Community-acquired pneumonia
Encyclopedia
Community-acquired pneumonia (CAP) is a term used to describe one of several disease
s in which individuals who have not recently been hospital
ized develop an infection
of the lung
s (pneumonia
). CAP is a common illness and can affect people of all ages. CAP often causes problems like difficulty in breathing, fever
, chest pain
s, and a cough
. CAP occurs because the areas of the lung which absorb oxygen
(alveoli) from the atmosphere
become filled with fluid and cannot work effectively.
CAP occurs throughout the world and is a leading cause of illness and death. Causes of CAP include bacteria
, virus
es, fungi, and parasites
. CAP can be diagnosed
by symptom
s and physical examination
alone, though x-ray
s, examination of the sputum
, and other tests are often used. Individuals with CAP sometimes require treatment
in a hospital
. CAP is primarily treated with antibiotic
medication
. Some forms of CAP can be prevented
by vaccination
.
Less common symptoms include:
The manifestations of pneumonia, like those for many conditions, might not be typical in older people. They might instead experience:
Additional symptoms for infants could include:
s, children, and adult
s are at risk for different spectrums of disease causing microorganisms. In addition, adults with chronic
illnesses, who live in certain parts of the world, who reside in nursing home
s, who have recently been treated with antibiotic
s, or who are alcoholics
are at risk for unique infections. Even when aggressive measures are taken, a definite cause for pneumonia is only identified in half the cases.
or by blood-borne infection across the placenta
. Infants can also inhale (aspirate
) fluid from the birth
canal as they are being born. The most important infection in newborns is caused by Streptococcus agalactiae
, also known as Group B Streptococcus or GBS. GBS causes at least 50% of cases of CAP in the first week of life. Other bacterial causes in the newborn period include Listeria monocytogenes and tuberculosis
. Viruses can also be transferred from mother to child; herpes simplex virus
is the most common and life-threatening, but adenovirus, mumps
, and enterovirus
can also cause disease.
CAP in older infants reflects increased exposure to microorganisms. Common bacterial causes include Streptococcus pneumoniae
, Escherichia coli
, Klebsiella pneumoniae
, Moraxella catarrhalis
, and Staphylococcus aureus
. A unique cause of CAP in this group is Chlamydia trachomatis
, which is acquired during birth but which does not cause pneumonia until 2–4 weeks later. Maternally-derived syphilis
can be a cause of CAP in this age group. Common viruses include respiratory syncytial virus (RSV), metapneumovirus
, adenovirus, parainfluenza, influenza
, and rhinovirus
. RSV in particular is a common source of illness and hospitalization. Fungi and parasites are not typically encountered in otherwise healthy infants.
, Chlamydophil pneumoniae, or Legionella pneumophila
. In contrast, older children and teenagers are more likely to acquire Mycoplasma pneumoniae
and Chlamydophila pneumoniae
than adults.
s. Identifying people at risk for these organisms is important for appropriate treatment.
Many less common organisms cause CAP. They are typically identified because an individual has special risk factors or after treatment for the common causes has failed. These rarer causes are covered in more detail in their specific pages: bacterial pneumonia
, viral pneumonia
, fungal pneumonia
, and parasitic pneumonia
.
Obstruction
When part of the airway (bronchi) leading to the alveoli is obstructed, the lung is not able to clear fluid when it accumulates. This can lead to infection of the fluid resulting in CAP. One cause of obstruction, especially in young children, is inhalation of a foreign object such as a marble or toy. The object is lodged in the small airways and pneumonia can form in the trapped areas of lung. Another cause of obstruction is lung cancer
, which can grow into the airways block the flow of air.
Lung disease
People with underlying lung disease are more likely to develop CAP. Diseases such as emphysema
or habits such as smoking
result in more frequent and more severe bouts of CAP. In children, recurrent episodes of CAP may be the first clue to diseases such as cystic fibrosis
or pulmonary sequestration
.
Immune problems
People who have immune system problems
are more likely to get CAP. People who have AIDS
are much more likely to develop CAP. Other immune problems range from severe immune deficiencies of childhood such as Wiskott-Aldrich syndrome
to less severe deficiencies such as common variable immunodeficiency
.
s and the immune system
's response to the infection. The mechanisms of infection are quite different for virus
es and the other microorganisms.
by a health provider may reveal fever, an increased respiratory rate
(tachypnea
), low blood pressure
(hypotension
), a fast heart rate
(tachycardia
), and/or changes in the amount of oxygen in the blood
. Feeling the way the chest expands (palpation
) and tapping the chest wall (percussion
) to identify dull areas which do not resonate
can identify areas of the lung which are stiff and full of fluid (consolidated). Examination of the lungs with the aid of a stethoscope
can reveal several things. A lack of normal breath sounds or the presence of crackling sounds (rales
) when the lungs are listened to (auscultated
) can also indicate consolidation. Increased vibration of the chest when speaking (tactile fremitus) and increased volume of whispered speech during auscultation
of the chest can also reveal consolidation.
X-ray
s of the chest, examination of the blood
and sputum
for infectious microorganisms, and blood tests
are commonly used to diagnose individuals with suspected CAP based upon symptoms and physical examination. The use of each test depends on the severity of illness, local practices, and the concern for any complication
s resulting from the infection.
All patients with CAP should have the amount of oxygen in their blood monitored with a machine called a pulse oximeter
. This helps determine how well the lungs are able to work despite infection. In some cases, analysis of arterial blood gas
may be required to accurately determine the amount of oxygen in the blood. Complete blood count
(CBC), a blood test, may reveal extra white blood cell
s, indicating an infection. Chest x-rays and chest computed tomography
(CT) can reveal areas of opacity
(seen as white) which represent consolidation. A normal chest x-ray makes CAP less likely; however, CAP is sometimes not seen on x-rays because the disease is either in its initial stages or involves a part of the lung not easily seen by x-ray. In some cases, chest CT can reveal a CAP which is not present on chest x-ray. X-rays can often be misleading, as many other diseases can mimic CAP such as heart problems
or other types of lung damage.
Several tests can be performed to identify the cause of an individual's CAP. Blood culture
s can be drawn to isolate any bacteria or fungi in the blood stream. Sputum Gram's stain and culture can also reveal the causative microorganism. In more severe cases, a procedure wherein a flexible scope is passed through the mouth into the lungs (bronchoscopy
) can be used to collect fluid for culture. Special tests can be performed if an uncommon microorganism is suspected (such as testing the urine for Legionella
antigen
when Legionnaires' disease
is a concern).
therapy). Additional consideration must be given to the setting in which the individual will be treated. Most people will be fully treated after taking oral pills while other people need to be hospitalized for intravenous antibiotics and, possibly, intensive care
. In general, all therapies in older children and adults will include treatment for atypical bacteria. Typically this is a macrolide antibiotic such as azithromycin
or clarithromycin
although a fluoroquinolone such as levofloxacin
can substitute. Doxycycline
is now the antibiotic of choice in the UK for complete coverage of the atypical bacteria. This is due to increased levels of clostridium difficile seen in hospital patients being linked to the increased use of clarithromycin
.
and gentamicin
for at least ten days. This treats the common bacteria Streptococcus agalactiae
, Listeria monocytogenes, and Escherichia coli
. If herpes simplex virus
is the cause, intravenous acyclovir is administered for 21 days.
for seven days is a common treatment. However, with increasing prevalence of DRSP, other agents such as cefpodoxime
will most likely become more popular in the future. Hospitalized children should receive intravenous ampicillin
, ceftriaxone
, or cefotaxime
. According to a recent meta-analysis a 3 days course of antibiotics seems to be sufficient for most cases of mild to moderate CAP in children.
For mild to moderate community-acquired pneumonia shorter courses of antibiotics (3–7 days) seem to be sufficient according to a recent meta-analysis.
s, such as the pneumonia severity index
and CURB-65 have been developed to help guide the decision. Factors which increase the need for hospitalization include age greater than 65; underlying chronic illnesses; a respiratory rate
greater than thirty breaths per minute; a systolic blood pressure
less than 90 mmHg; a heart rate
greater than 125 per minute; temperature
less than 35 or greater than 40°C; confusion; and evidence of infection outside the lung. Laboratory results which increase the need for hospitalization include arterial oxygen tension less than 60 mm Hg, carbon dioxide
of greater than 50 mmHg, or pH
less than 7.35 while breathing room air; hematocrit
less than 30%; creatinine
greater than 1.2 mg/dl or blood urea nitrogen
greater than 20 mg/ dl; white blood cell count less than 4 × 10^9/L or greater than 30 × 10^9/L; and absolute neutrophil count less than 1 x 10^9/L. X-ray findings which increase the need for hospitalization include involvement of more than one lobe of the lung
, presence of a cavity, and the presence of a pleural effusion
.
When CAP does not respond as expected, there are several possible causes. A complication of CAP may have occurred or a previously unknown health problem may be playing a role. Both situations are covered in more detail below. Additional causes include inappropriate antibiotics for the causative organism (i.e. DRSP), a previously unsuspected microorganism (such as tuberculosis
), or a condition which mimics CAP (such as Wegener's granulomatosis
). Additional testing may be performed and may include additional radiologic imaging (such as a computed tomography scan
) or a procedure such as a bronchoscopy
or lung biopsy
.
can occur when microorganisms enter the blood stream and the immune system
responds. Sepsis most often occurs with bacterial pneumonia
; Streptococcus pneumoniae is the most common cause. Individuals with sepsis require hospitalization in an intensive care unit. They often require medications and intravenous fluids to keep their blood pressure from going too low. Sepsis can cause liver, kidney, and heart damage among other things.
machine may be used. Otherwise, placement of a breathing tube into the mouth may be necessary and a ventilator
may be used to help the person breathe.
. If the microorganisms themselves are present, the fluid collection is often called an empyema
. If pleural fluid is present in a person with CAP, the fluid should be collected with a needle (thoracentesis
) and examined. Depending on the result of the examination, complete drainage of the fluid may be necessary, often with a chest tube
. If the fluid is not drained, bacteria can continue to cause illness because antibiotics do not penetrate well into the pleural cavity.
. Abscesses can be seen on an x-ray as a cavity within the lung. Abscesses typically occur in aspiration pneumonia
and most often contain a mixture of anaerobic bacteria
. Usually antibiotics are able to fully treat abscesses, but sometimes they must be drained by a surgeon
or radiologist
.
More cases of CAP occur during winter months than during other times of the year. CAP occurs more commonly in males than females and in blacks than Caucasians. Individuals with underlying illnesses such as Alzheimer's disease
, cystic fibrosis
, emphysema
, tobacco smoking
, alcoholism
, or immune system problems
are at increased risk for pneumonia.
is important not only for treatment of any underlying lung disease, but also because cigarette smoke interferes with many of the body's natural defenses against CAP.
Vaccination
is important in both children and adults. Vaccinations against Haemophilus influenzae
and Streptococcus pneumoniae
in the first year of life have greatly reduced their role in CAP in children. A vaccine against Streptococcus pneumoniae
is also available for adults and is currently recommended for all healthy individuals older than 65 and any adults with emphysema
, congestive heart failure
, diabetes mellitus
, cirrhosis
of the liver
, alcoholism
, cerebrospinal fluid
leaks, or who do not have a spleen
. A repeat vaccination may also be required after five or ten years.
Influenza
vaccines should be given yearly to the same individuals as receive vaccination against Streptococcus pneumoniae
. In addition, health care workers, nursing home residents, and pregnant women should receive the vaccine. When an influenza outbreak is occurring, medications such as amantadine
, rimantadine
, zanamivir, and oseltamivir
have been shown to prevent cases of influenza.
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
s in which individuals who have not recently been hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
ized develop an infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
of the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s (pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
). CAP is a common illness and can affect people of all ages. CAP often causes problems like difficulty in breathing, fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, chest pain
Chest pain
Chest pain may be a symptom of a number of serious conditions and is generally considered a medical emergency. Even though it may be determined that the pain is non-cardiac in origin, this is often a diagnosis of exclusion made after ruling out more serious causes of the pain.-Differential...
s, and a cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
. CAP occurs because the areas of the lung which absorb oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(alveoli) from the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
become filled with fluid and cannot work effectively.
CAP occurs throughout the world and is a leading cause of illness and death. Causes of CAP include bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es, fungi, and parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
. CAP can be diagnosed
Diagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
by symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s and physical examination
Physical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...
alone, though x-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s, examination of the sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
, and other tests are often used. Individuals with CAP sometimes require treatment
Pharmacotherapy
Pharmacotherapy is the treatment of disease through the administration of drugs. As such, it is considered part of the larger category of therapy....
in a hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
. CAP is primarily treated with antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
medication
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
. Some forms of CAP can be prevented
Preventive medicine
Preventive medicine or preventive care refers to measures taken to prevent diseases, rather than curing them or treating their symptoms...
by vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
.
Signs and symptoms
Symptoms of CAP commonly include:- dyspnea
- coughing that produces greenish or yellow sputumSputumSputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
- a high feverFeverFever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
that may be accompanied with sweating, chills, and uncontrollable shakingRigor (medicine)Rigor is a shaking occurring during a high fever. It occurs because cytokines and prostaglandins are released as part of an immune response and increase the set point for body temperature in the hypothalamus.... - sharp or stabbing chest pain
- rapid, shallow breathing that is often painful
Less common symptoms include:
- the coughing up of blood (hemoptysisHemoptysisHemoptysis or haemoptysis is the expectoration of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis is the expectoration (coughing up) of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis ...
) - headacheHeadacheA headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
s (including migraine headaches) - loss of appetiteAnorexia (symptom)Anorexia is the decreased sensation of appetite...
- excessive fatigue
- blueness of the skin (cyanosisCyanosisCyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
) - nauseaNauseaNausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
- vomitingVomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
- diarrheaDiarrheaDiarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
- joint pain (arthralgiaArthralgiaArthralgia literally means joint pain; it is a symptom of injury, infection, illnesses or an allergic reaction to medication....
) - muscle aches (myalgiaMyalgiaMyalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections...
)
The manifestations of pneumonia, like those for many conditions, might not be typical in older people. They might instead experience:
- new or worsening confusion
- hypothermiaHypothermiaHypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
- falls*
Additional symptoms for infants could include:
- being overly sleepy
- yellowing of the skin (jaundiceJaundiceJaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
) - difficulties feeding
Cause
There are over a hundred microorganisms which can cause CAP. The most common types of microorganisms are different among different groups of people. Newborn infantInfant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
s, children, and adult
Adult
An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....
s are at risk for different spectrums of disease causing microorganisms. In addition, adults with chronic
Chronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...
illnesses, who live in certain parts of the world, who reside in nursing home
Nursing home
A nursing home, convalescent home, skilled nursing unit , care home, rest home, or old people's home provides a type of care of residents: it is a place of residence for people who require constant nursing care and have significant deficiencies with activities of daily living...
s, who have recently been treated with antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s, or who are alcoholics
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
are at risk for unique infections. Even when aggressive measures are taken, a definite cause for pneumonia is only identified in half the cases.
Infants
Newborn infants can acquire lung infections prior to being born either by breathing infected amniotic fluidAmniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...
or by blood-borne infection across the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
. Infants can also inhale (aspirate
Pulmonary aspiration
Pulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...
) fluid from the birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...
canal as they are being born. The most important infection in newborns is caused by Streptococcus agalactiae
Streptococcus agalactiae
Streptococcus agalactiae is a beta-hemolytic Gram-positive streptococcus.- Identification :The CAMP test is an important test for identification...
, also known as Group B Streptococcus or GBS. GBS causes at least 50% of cases of CAP in the first week of life. Other bacterial causes in the newborn period include Listeria monocytogenes and tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
. Viruses can also be transferred from mother to child; herpes simplex virus
Herpes simplex virus
Herpes simplex virus 1 and 2 , also known as Human herpes virus 1 and 2 , are two members of the herpes virus family, Herpesviridae, that infect humans. Both HSV-1 and HSV-2 are ubiquitous and contagious...
is the most common and life-threatening, but adenovirus, mumps
Mumps
Mumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...
, and enterovirus
Enterovirus
Enteroviruses are a genus of ssRNA viruses associated with several human and mammalian diseases. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of antibody neutralization tests. Additional antigenic variants have been defined within several of the serotypes on the...
can also cause disease.
CAP in older infants reflects increased exposure to microorganisms. Common bacterial causes include Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S...
, Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
, Klebsiella pneumoniae
Klebsiella pneumoniae
Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines....
, Moraxella catarrhalis
Moraxella catarrhalis
Moraxella catarrhalis is a fastidious, nonmotile, Gram-negative, aerobic, oxidase-positive diplococcus that can cause infections of the respiratory system, middle ear, eye, central nervous system and joints of humans.-History:...
, and Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
. A unique cause of CAP in this group is Chlamydia trachomatis
Chlamydia trachomatis
Chlamydia trachomatis, an obligate intracellular human pathogen, is one of three bacterial species in the genus Chlamydia. C. trachomatis is a Gram-negative bacteria, therefore its cell wall components retain the counter-stain safranin and appear pink under a light microscope.The inclusion bodies...
, which is acquired during birth but which does not cause pneumonia until 2–4 weeks later. Maternally-derived syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
can be a cause of CAP in this age group. Common viruses include respiratory syncytial virus (RSV), metapneumovirus
Metapneumovirus
Human metapneumovirus is a negative single-stranded RNA virus of the family Paramyxoviridae and is closely related to the avian metapneumovirus subgroup C. It was isolated for the first time in 2001 in the Netherlands by using the RAP-PCR technique for identification of unknown viruses growing...
, adenovirus, parainfluenza, influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
, and rhinovirus
Rhinovirus
Human rhinoviruses are the most common viral infective agents in humans and are the predominant cause of the common cold. Rhinovirus infection proliferates in temperatures between 33–35 °C , and this may be why it occurs primarily in the nose...
. RSV in particular is a common source of illness and hospitalization. Fungi and parasites are not typically encountered in otherwise healthy infants.
Children
For the most part, children older than one month of life are at risk for the same microorganisms as adults. However, children less than five years are much less likely to have pneumonia caused by Mycoplasma pneumoniaeMycoplasma pneumoniae
Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes.It causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia, and is related to cold agglutinin disease.-Cell wall/Treatment:...
, Chlamydophil pneumoniae, or Legionella pneumophila
Legionella
Legionella is a pathogenic Gram negative bacterium, including species that cause legionellosis or Legionnaires' disease, most notably L. pneumophila. It may be readily visualized with a silver stain....
. In contrast, older children and teenagers are more likely to acquire Mycoplasma pneumoniae
Mycoplasma pneumoniae
Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes.It causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia, and is related to cold agglutinin disease.-Cell wall/Treatment:...
and Chlamydophila pneumoniae
Chlamydophila pneumoniae
Chlamydophila pneumoniae is a species of Chlamydophila, an obligate intracellular bacteria that infects humans and is a major cause of pneumonia....
than adults.
Adults
The full spectrum of microorganisms is responsible for CAP in adults. Several important groups of organisms are more common among people with certain risk factorRisk factor
In epidemiology, a risk factor is a variable associated with an increased risk of disease or infection. Sometimes, determinant is also used, being a variable associated with either increased or decreased risk.-Correlation vs causation:...
s. Identifying people at risk for these organisms is important for appropriate treatment.
- Viruses
- Viruses cause 20% of CAP cases. The most common viruses are influenzaInfluenzaInfluenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
, parainfluenza, respiratory syncytial virus, metapneumovirusMetapneumovirusHuman metapneumovirus is a negative single-stranded RNA virus of the family Paramyxoviridae and is closely related to the avian metapneumovirus subgroup C. It was isolated for the first time in 2001 in the Netherlands by using the RAP-PCR technique for identification of unknown viruses growing...
, and adenovirus. Less common viruses causing significant illness include chicken pox, SARS, avian fluH5N1Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...
, and hantavirusHantavirusHantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent waste products...
.
- Atypical organisms
- The most common bacterial causes of pneumonia are the so-called atypical bacteria Mycoplasma pneumoniaeMycoplasma pneumoniaeMycoplasma pneumoniae is a very small bacterium in the class Mollicutes.It causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia, and is related to cold agglutinin disease.-Cell wall/Treatment:...
and Chlamydophila pneumoniaeChlamydophila pneumoniaeChlamydophila pneumoniae is a species of Chlamydophila, an obligate intracellular bacteria that infects humans and is a major cause of pneumonia....
. Legionella pneumophilaLegionellaLegionella is a pathogenic Gram negative bacterium, including species that cause legionellosis or Legionnaires' disease, most notably L. pneumophila. It may be readily visualized with a silver stain....
is considered atypical but is less common. Atypical organisms are more difficult to grow, respond to different antibiotics, and were discovered more recently than the typical bacteria discovered in the early twentieth century.
- Streptococcus pneumoniae
- Streptococcus pneumoniaeStreptococcus pneumoniaeStreptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S...
is a common bacterial cause of CAP (most common cause in UK). Prior to the development of antibiotics and vaccination, it was a leading cause of death. Traditionally highly sensitive to penicillinPenicillinPenicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
, during the 1970s resistance to multiple antibiotics began to develop. Current strains of "drug resistant Streptococcus pneumoniae" or DRSP are common, accounting for twenty percent of all Streptococcus pneumoniae infections. Adults with risk factors for DRSP including being older than 65, having exposure to children in day careDay careChild care or day care is care of a child during the day by a person other than the child's legal guardians, typically performed by someone outside the child's immediate family...
, having alcoholism or other severe underlying disease, or recent treatment with antibiotics should initially be treated with antibiotics effective against DRSP.
- Hemophilus influenzae
- Hemophilus influenzaeHaemophilus influenzaeHaemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
is another common bacterial cause of CAP. First discovered in 1892, it was initially believed to be the cause of influenza because it commonly causes CAP in people who have suffered recent lung damage from viral pneumonia.
- Enteric Gram negative bacteria
- The enteric Gram negative bacteria such as Escherichia coliEscherichia coliEscherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
and Klebsiella pneumoniaeKlebsiella pneumoniaeKlebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines....
are a group of bacteria that typically live in the human intestinesColon (anatomy)The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
. Adults with risk factors for infection including residence in a nursing homeNursing homeA nursing home, convalescent home, skilled nursing unit , care home, rest home, or old people's home provides a type of care of residents: it is a place of residence for people who require constant nursing care and have significant deficiencies with activities of daily living...
, serious heartHeartThe heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
and lungLungThe lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
disease, and recent antibiotic use should initially be treated with antibiotics effective against Enteric Gram negative bacteria.
- Pseudomonas aeruginosa
- Pseudomonas aeruginosaPseudomonas aeruginosaPseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
is an uncommon cause of CAP but is a particularly difficult bacteria to treat. Individuals who are malnourished, have a lung disease called bronchiectasisBronchiectasisBronchiectasis is a disease state defined by localized, irreversible dilation of part of the bronchial tree caused by destruction of the muscle and elastic tissue. It is classified as an obstructive lung disease, along with emphysema, bronchitis, asthma, and cystic fibrosis...
, are on corticosteroids, or have recently had strong antibiotics for a week or more should initially be treated with antibiotics effective against Pseudomonas aeruginosa.
Many less common organisms cause CAP. They are typically identified because an individual has special risk factors or after treatment for the common causes has failed. These rarer causes are covered in more detail in their specific pages: bacterial pneumonia
Bacterial pneumonia
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.-Sign and symptoms:*Fever*Rigors*Cough*Dyspnea*Chest pain*Pneumococcal pneumonia can cause Hemoptysis-Gram positive:...
, viral pneumonia
Viral pneumonia
Viral pneumonia is a pneumonia caused by a virus.Viruses are one of the two major causes of pneumonia, the other being bacteria; less common causes are fungi and parasites...
, fungal pneumonia
Fungal pneumonia
Fungal pneumonia is an infection of the lungs by fungi. It can be caused by either endemic or opportunistic fungi or a combination of both. Case mortality in fungal pneumonias can be as high as 90% in immunocompromised patients, though immunocompetent patients generally respond well to anti-fungal...
, and parasitic pneumonia
Parasitic pneumonia
Parasitic pneumonia is an infection of the lungs by parasites. It is a rare cause of pneumonia, occurring almost exclusively in immunocompromised persons . This is a respiratory infection that may or may not be serious.There are a variety of parasites which can affect the lungs...
.
Risk factors
Some people have an underlying problem which increases their risk of getting an infection. Some important situations are covered below:Obstruction
When part of the airway (bronchi) leading to the alveoli is obstructed, the lung is not able to clear fluid when it accumulates. This can lead to infection of the fluid resulting in CAP. One cause of obstruction, especially in young children, is inhalation of a foreign object such as a marble or toy. The object is lodged in the small airways and pneumonia can form in the trapped areas of lung. Another cause of obstruction is lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
, which can grow into the airways block the flow of air.
Lung disease
People with underlying lung disease are more likely to develop CAP. Diseases such as emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
or habits such as smoking
Tobacco smoking
Tobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...
result in more frequent and more severe bouts of CAP. In children, recurrent episodes of CAP may be the first clue to diseases such as cystic fibrosis
Cystic fibrosis
Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...
or pulmonary sequestration
Pulmonary sequestration
A pulmonary sequestration, also known as a bronchopulmonary sequestration or a cystic lung lesion, is a medical condition where a piece of tissue that develops into lung tissue is not attached to the pulmonary arterial blood supply and does not communicate with the other...
.
Immune problems
People who have immune system problems
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...
are more likely to get CAP. People who have AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...
are much more likely to develop CAP. Other immune problems range from severe immune deficiencies of childhood such as Wiskott-Aldrich syndrome
Wiskott-Aldrich syndrome
Wiskott–Aldrich syndrome is a rare X-linked recessive disease characterized by eczema, thrombocytopenia , immune deficiency, and bloody diarrhea . It is also sometimes called the eczema-thrombocytopenia-immunodeficiency syndrome in keeping with Aldrich's original description in 1954...
to less severe deficiencies such as common variable immunodeficiency
Common variable immunodeficiency
Common variable immunodeficiency is a group of approximately 150 primary immunodeficiencies , which have a common set of symptoms but which have different underlying causes.Common variable immunodeficiency is the most commonly encountered primary immunodeficiency.-Causes and types:CVID...
.
Pathophysiology
The symptoms of CAP are the result of both the invasion of the lungs by microorganismMicroorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s and the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
's response to the infection. The mechanisms of infection are quite different for virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es and the other microorganisms.
- Viruses
- Viruses must invade cells in order to reproduce. Typically, a virus will reach the lungs by traveling in droplets through the mouthMouthThe mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
and noseHuman noseThe visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...
with inhalationInhalationInhalation is the movement of air from the external environment, through the air ways, and into the alveoli....
. There, the virus invades the cells lining the airways and the alveoli. This invasion often leads to cell death either through direct killing by the virus or by self-destruction through apoptosisApoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
. Further damage to the lungs occurs when the immune system responds to the infection. White blood cellWhite blood cellWhite blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
s, in particular lymphocyteLymphocyteA lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
s, are responsible for activating a variety of chemicals (cytokineCytokineCytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...
s) which cause leaking of fluid into the alveoli. The combination of cellular destruction and fluid-filled alveoli interrupts the transportation of oxygen into the bloodstream. In addition to the effects on the lungs, many viruses affect other organOrgan (anatomy)In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
s and can lead to illness affecting many different bodily functions. Viruses also make the body more susceptible to bacterial infection; for this reason, bacterial pneumonia often complicates viral CAP.
- Bacteria and fungi
- Bacteria and fungi also typically enter the lung with inhalation, though they can reach the lung through the bloodstream if other parts of the body are infected. Often, bacteria live in parts of the upper respiratory tractUpper respiratory tractThe upper respiratory tract or upper airway primarily refers to the parts of the respiratory system lying outside of the thorax or above the sternal angle. Another definition commomly used in medicine is the airway above the glottis or vocal cords...
and are constantly being inhaled into the alveoli. Once inside the alveoli, bacteriaBacteriaBacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and fungiFungusA fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
travel into the spaces between the cells and also between adjacent alveoli through connecting pores. This invasion triggers the immune systemImmune systemAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
to respond by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs. The neutrophils engulf and kill the offending organisms but also release cytokines which result in a general activation of the immune system. This results in the fever, chills, and fatigue common in CAP. The neutrophils, bacteria, and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation. Bacteria often travel from the lung into the blood stream and can result in serious illness such as septic shockSeptic shockSeptic shock is a medical emergency caused by decreased tissue perfusion and oxygen delivery as a result of severe infection and sepsis, though the microbe may be systemic or localized to a particular site. It can cause multiple organ dysfunction syndrome and death...
, in which there is low blood pressure leading to damage in multiple parts of the body including the brainBrainThe brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, kidneyKidneyThe kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, and heartHeartThe heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
.
- Parasites
- There are a variety of parasites which can affect the lungs. In general, these parasites enter the body through the skin or by being swallowed. Once inside the body, these parasites travel to the lungs, most often through the blood. There, a similar combination of cellular destruction and immune response causes disruption of oxygen transportation.
Diagnosis
Individuals with symptoms of CAP require further evaluation. Physical examinationPhysical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...
by a health provider may reveal fever, an increased respiratory rate
Respiratory rate
Respiratory rate is also known by respiration rate, pulmonary ventilation rate, ventilation rate, or breathing frequency is the number of breaths taken within a set amount of time, typically 60 seconds....
(tachypnea
Hyperventilation
Hyperventilation or overbreathing is the state of breathing faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide. It can result from a psychological state such as a panic attack, from a physiological condition such as metabolic acidosis, can be brought about by...
), low blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
(hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
), a fast heart rate
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
(tachycardia
Tachycardia
Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
), and/or changes in the amount of oxygen in the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
. Feeling the way the chest expands (palpation
Palpation
Palpation is used as part of a physical examination in which an object is felt to determine its size, shape, firmness, or location...
) and tapping the chest wall (percussion
Percussion (medicine)
Percussion is a method of tapping on a surface to determine the underlying structure, and is used in clinical examinations to assess the condition of the thorax or abdomen. It is one of the four methods of clinical examination, together with inspection, palpation and auscultation...
) to identify dull areas which do not resonate
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
can identify areas of the lung which are stiff and full of fluid (consolidated). Examination of the lungs with the aid of a stethoscope
Stethoscope
The stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of an animal body. It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins...
can reveal several things. A lack of normal breath sounds or the presence of crackling sounds (rales
Rales
Crackles, crepitations, or rales are the clicking, rattling, or crackling noises that may be made by one or both lungs of a human with a respiratory disease during inhalation. They are often heard only with a stethoscope...
) when the lungs are listened to (auscultated
Auscultation
Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
) can also indicate consolidation. Increased vibration of the chest when speaking (tactile fremitus) and increased volume of whispered speech during auscultation
Auscultation
Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
of the chest can also reveal consolidation.
X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s of the chest, examination of the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
and sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
for infectious microorganisms, and blood tests
Medical laboratory
A medical laboratory or clinical laboratory is a laboratory where tests are done on clinical specimens in order to get information about the health of a patient as pertaining to the diagnosis, treatment, and prevention of disease.-Departments:...
are commonly used to diagnose individuals with suspected CAP based upon symptoms and physical examination. The use of each test depends on the severity of illness, local practices, and the concern for any complication
Complication (medicine)
Complication, in medicine, is an unfavorable evolution of a disease, a health condition or a medical treatment. The disease can become worse in its severity or show a higher number of signs, symptoms or new pathological changes, become widespread throughout the body or affect other organ systems. A...
s resulting from the infection.
All patients with CAP should have the amount of oxygen in their blood monitored with a machine called a pulse oximeter
Pulse oximeter
A pulse oximeter is a medical device that indirectly monitors the oxygen saturation of a patient's blood and changes in blood volume in the skin, producing a photoplethysmograph. It is often attached to a medical monitor so staff can see a patient's oxygenation at all times...
. This helps determine how well the lungs are able to work despite infection. In some cases, analysis of arterial blood gas
Arterial blood gas
An arterial blood gas is a blood test that is performed using blood from an artery. It involves puncturing an artery with a thin needle and syringe and drawing a small volume of blood. The most common puncture site is the radial artery at the wrist, but sometimes the femoral artery in the groin or...
may be required to accurately determine the amount of oxygen in the blood. Complete blood count
Complete blood count
A complete blood count , also known as full blood count or full blood exam or blood panel, is a test panel requested by a doctor or other medical professional that gives information about the cells in a patient's blood...
(CBC), a blood test, may reveal extra white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
s, indicating an infection. Chest x-rays and chest computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
(CT) can reveal areas of opacity
Opacity (optics)
Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...
(seen as white) which represent consolidation. A normal chest x-ray makes CAP less likely; however, CAP is sometimes not seen on x-rays because the disease is either in its initial stages or involves a part of the lung not easily seen by x-ray. In some cases, chest CT can reveal a CAP which is not present on chest x-ray. X-rays can often be misleading, as many other diseases can mimic CAP such as heart problems
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
or other types of lung damage.
Blood culture
Blood culture is a microbiological culture of blood. It is employed to detect infections that are spreading through the bloodstream...
s can be drawn to isolate any bacteria or fungi in the blood stream. Sputum Gram's stain and culture can also reveal the causative microorganism. In more severe cases, a procedure wherein a flexible scope is passed through the mouth into the lungs (bronchoscopy
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
) can be used to collect fluid for culture. Special tests can be performed if an uncommon microorganism is suspected (such as testing the urine for Legionella
Legionella
Legionella is a pathogenic Gram negative bacterium, including species that cause legionellosis or Legionnaires' disease, most notably L. pneumophila. It may be readily visualized with a silver stain....
antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
when Legionnaires' disease
Legionellosis
Legionellosis is a potentially fatal infectious disease caused by gram negative, aerobic bacteria belonging to the genus Legionella. Over 90% of legionellosis cases are caused by Legionella pneumophila, a ubiquitous aquatic organism that thrives in temperatures between , with an optimum temperature...
is a concern).
Treatment
CAP is treated by administering an antibiotic which is effective in killing the offending microorganism as well as managing any complications of the infection. If the causative microorganism is unidentified, different antibiotics are tested in the laboratory in order to identify which medication will be most effective. Often, however, no microorganism is ever identified. Also, since laboratory testing can take several days, there is some delay until an organism is identified. In both cases, a person's risk factors for different organisms must be remembered when choosing the initial antibiotics (called empiricEmpiricism
Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...
therapy). Additional consideration must be given to the setting in which the individual will be treated. Most people will be fully treated after taking oral pills while other people need to be hospitalized for intravenous antibiotics and, possibly, intensive care
Intensive care medicine
Intensive-care medicine or critical-care medicine is a branch of medicine concerned with the diagnosis and management of life threatening conditions requiring sophisticated organ support and invasive monitoring.- Overview :...
. In general, all therapies in older children and adults will include treatment for atypical bacteria. Typically this is a macrolide antibiotic such as azithromycin
Azithromycin
Azithromycin is an azalide, a subclass of macrolide antibiotics. Azithromycin is one of the world's best-selling antibiotics...
or clarithromycin
Clarithromycin
Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...
although a fluoroquinolone such as levofloxacin
Levofloxacin
Levofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class and is used to treat severe or life-threatening bacterial infections or bacterial infections that have failed to respond to other antibiotic classes. It is sold under various brand names, such as Levaquin and...
can substitute. Doxycycline
Doxycycline
Doxycycline INN is a member of the tetracycline antibiotics group, and is commonly used to treat a variety of infections. Doxycycline is a semisynthetic tetracycline invented and clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand name Vibramycin. Vibramycin...
is now the antibiotic of choice in the UK for complete coverage of the atypical bacteria. This is due to increased levels of clostridium difficile seen in hospital patients being linked to the increased use of clarithromycin
Clarithromycin
Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...
.
Newborns
Most newborn infants with CAP are hospitalized and given intravenous ampicillinAmpicillin
Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...
and gentamicin
Gentamicin
Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...
for at least ten days. This treats the common bacteria Streptococcus agalactiae
Streptococcus agalactiae
Streptococcus agalactiae is a beta-hemolytic Gram-positive streptococcus.- Identification :The CAMP test is an important test for identification...
, Listeria monocytogenes, and Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
. If herpes simplex virus
Herpes simplex virus
Herpes simplex virus 1 and 2 , also known as Human herpes virus 1 and 2 , are two members of the herpes virus family, Herpesviridae, that infect humans. Both HSV-1 and HSV-2 are ubiquitous and contagious...
is the cause, intravenous acyclovir is administered for 21 days.
Children
Treatment of CAP in children depends on both the age of the child and the severity of his/her illness. Children less than five do not typically receive treatment to cover atypical bacteria. If a child does not need to be hospitalized, amoxicillinAmoxicillin
Amoxicillin , formerly amoxycillin , and abbreviated amox, is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral...
for seven days is a common treatment. However, with increasing prevalence of DRSP, other agents such as cefpodoxime
Cefpodoxime
Cefpodoxime is an oral third generation cephalosporin antibiotic. It is marketed as the prodrug cefpodoxime proxetil by Pharmacia & Upjohn under the trade name Vantin. It is active against most Gram positive and Gram negative organisms. Notable exceptions include Pseudomonas aeruginosa,...
will most likely become more popular in the future. Hospitalized children should receive intravenous ampicillin
Ampicillin
Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...
, ceftriaxone
Ceftriaxone
Ceftriaxone is a third-generation cephalosporin antibiotic. Like other third-generation cephalosporins, it has broad spectrum activity against Gram-positive and Gram-negative bacteria. In most cases, it is considered to be equivalent to cefotaxime in terms of safety and efficacy...
, or cefotaxime
Cefotaxime
Cefotaxime is a third-generation cephalosporin antibiotic. Like other third-generation cephalosporins, it has broad spectrum activity against Gram positive and Gram negative bacteria...
. According to a recent meta-analysis a 3 days course of antibiotics seems to be sufficient for most cases of mild to moderate CAP in children.
Adults
In 2001, the American Thoracic Society, drawing on work by the British and Canadian Thoracic Societies, established guidelines for the management of adults with CAP which divided individuals with CAP into four categories based upon common organisms encountered.- Healthy outpatients without risk factors
- This group, the largest, is composed of otherwise healthy patients without risk factors for DRSP, enteric Gram negative bacteria, Pseudomonas, or other less common causes of CAP. The primary microoganisms in this group are viruses, atypical bacteria, penicillin sensitive Streptococcus pneumoniae, and Hemophilus influenzae. Recommended management is with a macrolide antibiotic such as azithromycinAzithromycinAzithromycin is an azalide, a subclass of macrolide antibiotics. Azithromycin is one of the world's best-selling antibiotics...
or clarithromycinClarithromycinClarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...
for seven to ten days.
- Outpatients with underlying illness and/or risk factors
- This group does not require hospitalization; its members either have underlying health problems (such as emphysemaEmphysemaEmphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
or congestive heart failureCongestive heart failureHeart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
) or is at risk for DRSP and/or enteric Gram negative bacteria. Treatment is with a fluoroquinolone active against Streptococcus pneumoniae such as levofloxacinLevofloxacinLevofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class and is used to treat severe or life-threatening bacterial infections or bacterial infections that have failed to respond to other antibiotic classes. It is sold under various brand names, such as Levaquin and...
or a beta-lactam antibioticBeta-lactam antibioticβ-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in its molecular structure. This includes penicillin derivatives , cephalosporins , monobactams, and carbapenems...
such as cefpodoximeCefpodoximeCefpodoxime is an oral third generation cephalosporin antibiotic. It is marketed as the prodrug cefpodoxime proxetil by Pharmacia & Upjohn under the trade name Vantin. It is active against most Gram positive and Gram negative organisms. Notable exceptions include Pseudomonas aeruginosa,...
, cefuroximeCefuroximeCefuroxime is a second-generation cephalosporin antibiotic that has been widely available in the USA as Ceftin since 1977. GlaxoSmithKline sells the antibiotic in the United Kingdom under the name Zinnat.-Indications:As for the other cephalosporins, although as a...
, amoxicillinAmoxicillinAmoxicillin , formerly amoxycillin , and abbreviated amox, is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral...
, or amoxicillin/clavulanateCo-amoxiclavAmoxicillin/clavulanic acid or co-amoxiclav is a combination antibiotic consisting of amoxicillin trihydrate, a β-lactam antibiotic, and potassium clavulanate, a β-lactamase inhibitor...
plus a macrolide antibiotic such as azithromycinAzithromycinAzithromycin is an azalide, a subclass of macrolide antibiotics. Azithromycin is one of the world's best-selling antibiotics...
or clarithromycinClarithromycinClarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...
for seven to ten days.
- Hospitalized individuals not at risk for Pseudomonas
- This group requires hospitalization and administration of intravenous antibiotics. Treatment is with either an intravenous fluoroquinolone active against Streptococcus pneumoniae such as levofloxacinLevofloxacinLevofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class and is used to treat severe or life-threatening bacterial infections or bacterial infections that have failed to respond to other antibiotic classes. It is sold under various brand names, such as Levaquin and...
or beta-lactam antibioticBeta-lactam antibioticβ-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in its molecular structure. This includes penicillin derivatives , cephalosporins , monobactams, and carbapenems...
such as cefotaxime, ceftriaxone, ampicillin/sulbactam, or high-dose ampicillin plus an intravenous macrolide antibiotic such as azithromycinAzithromycinAzithromycin is an azalide, a subclass of macrolide antibiotics. Azithromycin is one of the world's best-selling antibiotics...
or clarithromycinClarithromycinClarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...
for seven to ten days.
- Individuals requiring intensive care at risk for Pseudomonas
- Individuals being treated in an intensive care unit with risk factors for infection with Pseudomonas aeruginosa require specific antibiotics targeting this difficult to eradicate bacteria. One possible regimen is an intravenous antipseudomonal beta-lactam such as cefepimeCefepimeCefepime is a fourth-generation cephalosporin antibiotic developed in 1994. Cefepime has an extended spectrum of activity against Gram-positive and Gram-negative bacteria, with greater activity against both Gram-negative and Gram-positive organisms than third-generation agents...
, imipenemImipenemImipenem is an intravenous β-lactam antibiotic developed in 1980. It has an extremely broad spectrum of activity.Imipenem belongs to the subgroup of carbapenems. It is derived from a compound called thienamycin, which is produced by the bacterium Streptomyces cattleya...
, meropenemMeropenemMeropenem is an ultra-broad spectrum injectable antibiotic used to treat a wide variety of infections, including meningitis and pneumonia. It is a beta-lactam and belongs to the subgroup of carbapenem, similar to imipenem and ertapenem. Meropenem was originally developed by Sumitomo Pharmaceuticals...
, or piperacillin/tazobactamPiperacillinPiperacillin is an extended spectrum beta-lactam antibiotic of the ureidopenicillin class.It is normally used together with a beta-lactamase inhibitor such as tazobactam. The combination drug piperacillin/tazobactam is commercially available as e.g. Tazocin, Zosyn, Brodactam, Piptaz and as Trezora...
plus an intravenous antipseudomonal fluoroquinolone such as levofloxacinLevofloxacinLevofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class and is used to treat severe or life-threatening bacterial infections or bacterial infections that have failed to respond to other antibiotic classes. It is sold under various brand names, such as Levaquin and...
. Another recommended regimen is an intravenous antipseudomonal beta-lactam such as cefepime, imipenem, meropenem, or piperacillin/ tazobactam plus an intravenous aminoglycoside such as gentamicinGentamicinGentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...
or tobramycin plus either an intravenous macrolide such azithromycin or an intravenous nonpseudomonal fluoroquinolone such as ciprofloxacinCiprofloxacinCiprofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class.It is a second-generation fluoroquinolone antibacterial. It kills bacteria by interfering with the enzymes that cause DNA to rewind after being copied, which stops synthesis of DNA and of...
.
For mild to moderate community-acquired pneumonia shorter courses of antibiotics (3–7 days) seem to be sufficient according to a recent meta-analysis.
Hospitalize
Some people with CAP require hospitalization and more intensive care than the majority. In general, a discussion between the individual and his or her health care provider determines the need for hospitalization. Clinical prediction ruleClinical prediction rule
A clinical prediction rule is type of medical research study in which researchers try to identify the best combination of medical sign, symptoms, and other findings in predicting the probability of a specific disease or outcome....
s, such as the pneumonia severity index
Pneumonia severity index
The pneumonia severity index [PSI] or PORT Score is a clinical prediction rule that medical practitioners can use to calculate the probability of morbidity and mortality among patients with community acquired pneumonia....
and CURB-65 have been developed to help guide the decision. Factors which increase the need for hospitalization include age greater than 65; underlying chronic illnesses; a respiratory rate
Respiratory rate
Respiratory rate is also known by respiration rate, pulmonary ventilation rate, ventilation rate, or breathing frequency is the number of breaths taken within a set amount of time, typically 60 seconds....
greater than thirty breaths per minute; a systolic blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
less than 90 mmHg; a heart rate
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
greater than 125 per minute; temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
less than 35 or greater than 40°C; confusion; and evidence of infection outside the lung. Laboratory results which increase the need for hospitalization include arterial oxygen tension less than 60 mm Hg, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
of greater than 50 mmHg, or pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
less than 7.35 while breathing room air; hematocrit
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...
less than 30%; creatinine
Creatinine
Creatinine is a break-down product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body...
greater than 1.2 mg/dl or blood urea nitrogen
Blood urea nitrogen
The blood urea nitrogen test is a measure of the amount of nitrogen in the blood in the form of urea, and a measurement of renal function. Urea is a by- product from metabolism of proteins by the liver and is removed from the blood by the kidneys.-Physiology:The liver produces urea in the urea...
greater than 20 mg/ dl; white blood cell count less than 4 × 10^9/L or greater than 30 × 10^9/L; and absolute neutrophil count less than 1 x 10^9/L. X-ray findings which increase the need for hospitalization include involvement of more than one lobe of the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
, presence of a cavity, and the presence of a pleural effusion
Pleural effusion
Pleural effusion is excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation.-Pathophysiology:...
.
Prognosis
Individuals who are treated for CAP outside of the hospital have a mortality rate less than 1%. Fever typically responds in the first two days of therapy and other symptoms resolve in the first week. The x-ray, however, may remain abnormal for at least a month, even when CAP has been successfully treated. Among individuals who require hospitalization, the mortality rate averages 12% overall, but is as much as 40% in people who have bloodstream infections or require intensive care. Factors which increase mortality are the same as those which increase the need for hospitalization and are listed above.When CAP does not respond as expected, there are several possible causes. A complication of CAP may have occurred or a previously unknown health problem may be playing a role. Both situations are covered in more detail below. Additional causes include inappropriate antibiotics for the causative organism (i.e. DRSP), a previously unsuspected microorganism (such as tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
), or a condition which mimics CAP (such as Wegener's granulomatosis
Wegener's granulomatosis
Wegener's granulomatosis , more recently granulomatosis with polyangiitis , is an incurable form of vasculitis that affects the nose, lungs, kidneys and other organs. Due to its end-organ damage, it is life-threatening and requires long-term immunosuppression...
). Additional testing may be performed and may include additional radiologic imaging (such as a computed tomography scan
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
) or a procedure such as a bronchoscopy
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
or lung biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
.
Complications
Despite appropriate antibiotic therapy, severe complications can result from CAP, including:Sepsis
SepsisSepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
can occur when microorganisms enter the blood stream and the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
responds. Sepsis most often occurs with bacterial pneumonia
Bacterial pneumonia
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.-Sign and symptoms:*Fever*Rigors*Cough*Dyspnea*Chest pain*Pneumococcal pneumonia can cause Hemoptysis-Gram positive:...
; Streptococcus pneumoniae is the most common cause. Individuals with sepsis require hospitalization in an intensive care unit. They often require medications and intravenous fluids to keep their blood pressure from going too low. Sepsis can cause liver, kidney, and heart damage among other things.
Respiratory failure
Because CAP affects the lungs, often individuals with CAP have difficulty breathing. If enough of the lung is involved, it may not be possible for a person to breathe enough to live without support. Non-invasive machines such as a bilevel positive airway pressureBilevel positive airway pressure
Bilevel positive airway pressure is a continuous positive airway pressure mode used during noninvasive positive pressure ventilation. It delivers a preset inspiratory positive airway pressure and expiratory positive airway pressure . BPAP can be described as a Continuous Positive Airway...
machine may be used. Otherwise, placement of a breathing tube into the mouth may be necessary and a ventilator
Medical ventilator
A medical ventilator can be defined as any machine designed to mechanically move breatheable air into and out of the lungs, to provide the mechanism of breathing for a patient who is physically unable to breathe, or breathing insufficiently....
may be used to help the person breathe.
Pleural effusion and empyema
Occasionally, microorganisms from the lung will cause fluid to form in the space surrounding the lung, called the pleural cavityPleural cavity
In human anatomy, the pleural cavity is the potential space between the two pleura of the lungs. The pleura is a serous membrane which folds back onto itself to form a two-layered, membrane structure. The thin space between the two pleural layers is known as the pleural cavity; it normally...
. If the microorganisms themselves are present, the fluid collection is often called an empyema
Empyema
Pleural empyema is an accumulation of pus in the pleural cavity. Most pleural empyemas arise from an infection within the lung , often associated with parapneumonic effusions. There are three stages: exudative, fibrinopurulent and organizing. In the exudative stage, the pus accumulates...
. If pleural fluid is present in a person with CAP, the fluid should be collected with a needle (thoracentesis
Thoracentesis
Thoracentesis , also known as thoracocentesis or pleural tap, is an invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes. A cannula, or hollow needle, is carefully introduced into the thorax, generally after administration of local anesthesia...
) and examined. Depending on the result of the examination, complete drainage of the fluid may be necessary, often with a chest tube
Chest tube
A chest tube is a flexible plastic tube that is inserted through the side of the chest into the pleural space. It is used to remove air or fluid , or pus from the intrathoracic space...
. If the fluid is not drained, bacteria can continue to cause illness because antibiotics do not penetrate well into the pleural cavity.
Abscess
Rarely, microorganisms in the lung will form a pocket of fluid and bacteria called an abscessAbscess
An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...
. Abscesses can be seen on an x-ray as a cavity within the lung. Abscesses typically occur in aspiration pneumonia
Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents...
and most often contain a mixture of anaerobic bacteria
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
. Usually antibiotics are able to fully treat abscesses, but sometimes they must be drained by a surgeon
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
or radiologist
Interventional radiology
Interventional radiology is a specialty of radiology, in which image-guided procedures are used to diagnose and treat a multitude of diseases across all body systems...
.
Epidemiology
CAP is a common illness in all parts of the world. It is a major cause of death among all age groups. In children, the majority of deaths occur in the newborn period, with over two million worldwide deaths a year. In fact, the WHO estimates that one in three newborn infant deaths are due to pneumonia. Mortality decreases with age until late adulthood; elderly individuals are particularly at risk for CAP and associated mortality.More cases of CAP occur during winter months than during other times of the year. CAP occurs more commonly in males than females and in blacks than Caucasians. Individuals with underlying illnesses such as Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
, cystic fibrosis
Cystic fibrosis
Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...
, emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
, tobacco smoking
Tobacco smoking
Tobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...
, alcoholism
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
, or immune system problems
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
are at increased risk for pneumonia.
Prevention
In addition to treating any underlying illness which can increase a person's risk for CAP, there are several additional ways to prevent CAP. Smoking cessationSmoking cessation
Smoking cessation is the process of discontinuing the practice of inhaling a smoked substance. This article focuses exclusively on cessation of tobacco smoking; however, the methods described may apply to cessation of smoking other substances that can be difficult to stop using due to the...
is important not only for treatment of any underlying lung disease, but also because cigarette smoke interferes with many of the body's natural defenses against CAP.
Vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
is important in both children and adults. Vaccinations against Haemophilus influenzae
Haemophilus influenzae
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
and Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S...
in the first year of life have greatly reduced their role in CAP in children. A vaccine against Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S...
is also available for adults and is currently recommended for all healthy individuals older than 65 and any adults with emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
, congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
, diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, cirrhosis
Cirrhosis
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...
of the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, alcoholism
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
, cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
leaks, or who do not have a spleen
Asplenia
Asplenia refers to the absence of normal spleen function and is associated with some serious infection risks. Hyposplenism is used to describe reduced splenic functioning, but not as severely affected as with asplenism.-Congenital:...
. A repeat vaccination may also be required after five or ten years.
Influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
vaccines should be given yearly to the same individuals as receive vaccination against Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S...
. In addition, health care workers, nursing home residents, and pregnant women should receive the vaccine. When an influenza outbreak is occurring, medications such as amantadine
Amantadine
Amantadine is the organic compound known formally as 1-adamantylamine or 1-aminoadamantane. The molecule consists of adamantane backbone that has an amino group substituted at one of the four methyne positions. This pharmaceutical is sold under the name Symmetrel for use both as an antiviral and an...
, rimantadine
Rimantadine
Rimantadine is an orally administered antiviral drug used to treat, and in rare cases prevent, influenzavirus A infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Both rimantadine and the similar drug...
, zanamivir, and oseltamivir
Oseltamivir
Oseltamivir INN , an antiviral drug, slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell; median time to symptom alleviation is reduced by 0.5–1 day. The drug is sold under the trade name Tamiflu, and is taken orally...
have been shown to prevent cases of influenza.