Chlamydophila pneumoniae
Encyclopedia
Chlamydophila pneumoniae is a species of Chlamydophila
, an obligate intracellular
bacteria that infects humans and is a major cause of pneumonia
.
It was known as the TWAR (Taiwan Acute Respiratory) agent from the names of the two original isolates - Taiwan (TW-183) and an acute respiratory isolate designated AR-39.
Until recently it was known as Chlamydia pneumoniae, and that name is used as an alternate in some sources. In some cases, to avoid confusion, both names are given.
C. pneumoniae has a complex life cycle and must infect another cell in order to reproduce; thus it is classified as an obligate intracellular pathogen
. The full genome
sequence for C. pneumoniae was published in 1999.
C. pneumoniae also infects and causes disease in Koala
s, emerald tree boa (Corallus caninus), iguana
s, chameleon
s, frogs, and turtles.
The first known case of infection with C. pneumoniae was a case of sinusitis in Taiwan.
This atypical bacterium commonly causes pharyngitis
, bronchitis
and atypical pneumonia
mainly in elderly and debilitated patients but in healthy adults also.
) that undergoes several transformations during its life cycle. It exists as an elementary body (EB) in between host
s. The EB is not biologically active but is resistant to environment
al stresses and can survive outside of a host for a limited time. The EB travels from an infected
person to the lung
s of a non-infected person in small droplets and is responsible for infection. Once in the lungs, the EB is taken up by cell
s in a pouch called an endosome
by a process called phagocytosis. However, the EB is not destroyed by fusion with lysosome
s as is typical for phagocytosed material. Instead, it transforms into a reticulate body and begins to replicate within the endosome. The reticulate bodies must utilize some of the host's cellular machinery to complete its replication. The reticulate bodies then convert back to elementary bodies and are released back into the lung, often after causing the death of the host cell. The EBs are thereafter able to infect new cells, either in the same organism
or in a new host. Thus, the life cycle of C. pneumoniae is divided between the elementary body, which is able to infect new hosts but can not replicate, and the reticulate body ,which replicates but is not able to cause new infection.
. Because treatment and diagnosis are different from historically recognized causes such as Streptococcus pneumoniae
, pneumonia caused by C. pneumoniae is categorized as an "atypical pneumonia
."
(infection
and inflammation
of the brain
and meninges
), arthritis
, myocarditis
(inflammation of the heart
), and Guillain-Barré syndrome
.
. One meta-analysis
of studies looking at associating serological data showing prior C. pneumoniae infection in patients with and without lung cancer found results suggesting prior infection was associated with a small increased risk of developing lung cancer. The authors of this study suggested further research should be conducted using larger populations and more methodologically robust study design
to confirm this result.
and coronary artery disease. Serological testing, direct pathologic analysis of plaques and in vitro testing suggest chronic infection with C. pneumoniae may be a risk factor for development of atherosclerotic plaques. C. pneumoniae infection increases adherence of macrophages to endothelial cells in vitro and ex vivo. However, the current data does not define how often C. pneumoniae is found in atherosclerotic or normal vascular
tissue nor does it allow for determining whether C. pneumoniae infection has a causative effect on atheroma formation or is merely an "innocent passenger" in these plaques. The largest trials that studied the use of antibiotics as a prevention for diseases associated with atherosclerosis such as heart attacks and strokes did not show any significant difference between antibiotics and placebo
.
C. pneumoniae has also been found in the cerebrospinal fluid of some patients diagnosed with multiple sclerosis.
Chlamydophila
Chlamydophila is a bacterial genus belonging to the family Chlamydiaceae, order Chlamydiales, class/phylum Chlamydiae.-Taxonomy:Chlamydophila was recognized in 1999, with six species in Chlamydophila and three in the original genus, Chlamydia...
, an obligate intracellular
Obligate intracellular parasite
Intracellular parasites are parasitic microorganisms - microparasites that are capable of growing and reproducing inside the cells of a host.-Facultative:...
bacteria that infects humans and is a major cause of 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...
.
It was known as the TWAR (Taiwan Acute Respiratory) agent from the names of the two original isolates - Taiwan (TW-183) and an acute respiratory isolate designated AR-39.
Until recently it was known as Chlamydia pneumoniae, and that name is used as an alternate in some sources. In some cases, to avoid confusion, both names are given.
C. pneumoniae has a complex life cycle and must infect another cell in order to reproduce; thus it is classified as an obligate intracellular pathogen
Obligate intracellular parasite
Intracellular parasites are parasitic microorganisms - microparasites that are capable of growing and reproducing inside the cells of a host.-Facultative:...
. The full genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
sequence for C. pneumoniae was published in 1999.
C. pneumoniae also infects and causes disease in Koala
Koala
The koala is an arboreal herbivorous marsupial native to Australia, and the only extant representative of the family Phascolarctidae....
s, emerald tree boa (Corallus caninus), iguana
Iguana
Iguana is a herbivorous genus of lizard native to tropical areas of Central America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena...
s, chameleon
Chameleon
Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...
s, frogs, and turtles.
The first known case of infection with C. pneumoniae was a case of sinusitis in Taiwan.
This atypical bacterium commonly causes pharyngitis
Pharyngitis
Pharyngitis is an inflammation of the throat or pharynx. In most cases it is quite painful, and is the most common cause of a sore throat.Like many types of inflammation, pharyngitis can be acute – characterized by a rapid onset and typically a relatively short course – or chronic....
, bronchitis
Bronchitis
Acute bronchitis is an inflammation of the large bronchi in the lungs that is usually caused by viruses or bacteria and may last several days or weeks. Characteristic symptoms include cough, sputum production, and shortness of breath and wheezing related to the obstruction of the inflamed airways...
and atypical pneumonia
Atypical pneumonia
Atypical pneumonia aka "walking pneumonia" is a pneumonia not caused by one of the more traditional pathogens, and with a clinical presentation inconsistent with typical pneumonia. It can be caused by a variety of microorganisms...
mainly in elderly and debilitated patients but in healthy adults also.
Life cycle and method of infection
Chlamydophila pneumoniae is a small bacterium (0.2 to 1 micrometerMicrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
) that undergoes several transformations during its life cycle. It exists as an elementary body (EB) in between host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
s. The EB is not biologically active but is resistant to environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
al stresses and can survive outside of a host for a limited time. The EB travels from an infected
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...
person to 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 of a non-infected person in small droplets and is responsible for infection. Once in the lungs, the EB is taken up by cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s in a pouch called an endosome
Endosome
In biology, an endosome is a membrane-bound compartment inside eukaryotic cells. It is a compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome. Molecules internalized from the plasma membrane can follow this pathway all the way to lysosomes for...
by a process called phagocytosis. However, the EB is not destroyed by fusion with lysosome
Lysosome
thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...
s as is typical for phagocytosed material. Instead, it transforms into a reticulate body and begins to replicate within the endosome. The reticulate bodies must utilize some of the host's cellular machinery to complete its replication. The reticulate bodies then convert back to elementary bodies and are released back into the lung, often after causing the death of the host cell. The EBs are thereafter able to infect new cells, either in the same organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
or in a new host. Thus, the life cycle of C. pneumoniae is divided between the elementary body, which is able to infect new hosts but can not replicate, and the reticulate body ,which replicates but is not able to cause new infection.
Pneumonia
C. pneumoniae is a common cause of pneumonia around the world. C. pneumoniae is typically acquired by otherwise healthy people and is a form of community-acquired pneumoniaCommunity-acquired pneumonia
Community-acquired pneumonia is a term used to describe one of several diseases in which individuals who have not recently been hospitalized develop an infection of the lungs . CAP is a common illness and can affect people of all ages. CAP often causes problems like difficulty in breathing, fever,...
. Because treatment and diagnosis are different from historically recognized causes such as 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...
, pneumonia caused by C. pneumoniae is categorized as an "atypical pneumonia
Atypical pneumonia
Atypical pneumonia aka "walking pneumonia" is a pneumonia not caused by one of the more traditional pathogens, and with a clinical presentation inconsistent with typical pneumonia. It can be caused by a variety of microorganisms...
."
Other illnesses
In addition to pneumonia, C. pneumoniae less commonly causes several other illnesses. Among these are meningoencephalitisMeningoencephalitis
Meningoencephalitis is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain.-Causes:...
(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...
and inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the brain
Brain
The 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,...
and meninges
Meninges
The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...
), arthritis
Arthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....
, myocarditis
Myocarditis
Myocarditis is inflammation of heart muscle . It resembles a heart attack but coronary arteries are not blocked.Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly non-viral pathogens such as Borrelia burgdorferi or Trypanosoma cruzi, or as a...
(inflammation of the heart
Heart
The 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 Guillain-Barré syndrome
Guillain-Barré syndrome
Guillain–Barré syndrome , sometimes called Landry's paralysis, is an acute inflammatory demyelinating polyneuropathy , a disorder affecting the peripheral nervous system. Ascending paralysis, weakness beginning in the feet and hands and migrating towards the trunk, is the most typical symptom...
.
Association with lung cancer
Multiple studies have studied whether there is an association between prior C. pneumoniae infection and lung cancerLung 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...
. One meta-analysis
Meta-analysis
In statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. In its simplest form, this is normally by identification of a common measure of effect size, for which a weighted average might be the output of a meta-analyses. Here the...
of studies looking at associating serological data showing prior C. pneumoniae infection in patients with and without lung cancer found results suggesting prior infection was associated with a small increased risk of developing lung cancer. The authors of this study suggested further research should be conducted using larger populations and more methodologically robust study design
Study design
Clinical study design is the formulation of trials and experiments in medical and epidemiological research, sometimes known as clinical trials. Many of the considerations here are shared under the more general topic of design of experiments but there can be others, in particular related to patient...
to confirm this result.
Links with chronic diseases
There has been considerable research into the association between C. pneumoniae infection and atherosclerosisAtherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
and coronary artery disease. Serological testing, direct pathologic analysis of plaques and in vitro testing suggest chronic infection with C. pneumoniae may be a risk factor for development of atherosclerotic plaques. C. pneumoniae infection increases adherence of macrophages to endothelial cells in vitro and ex vivo. However, the current data does not define how often C. pneumoniae is found in atherosclerotic or normal vascular
Vascular
Vascular in zoology and medicine means "related to blood vessels", which are part of the circulatory system. An organ or tissue that is vascularized is heavily endowed with blood vessels and thus richly supplied with blood....
tissue nor does it allow for determining whether C. pneumoniae infection has a causative effect on atheroma formation or is merely an "innocent passenger" in these plaques. The largest trials that studied the use of antibiotics as a prevention for diseases associated with atherosclerosis such as heart attacks and strokes did not show any significant difference between antibiotics and placebo
Placebo
A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
.
C. pneumoniae has also been found in the cerebrospinal fluid of some patients diagnosed with multiple sclerosis.