Bordetella pertussis
Encyclopedia
Bordetella pertussis is a Gram-negative
, aerobic
coccobacillus
of the genus Bordetella
, and the causative agent of pertussis
or whooping cough. Unlike B. bronchiseptica
, B. pertussis is non-motile. Its virulence factors include pertussis toxin, filamentous hæmagglutinin
, pertactin
, fimbria
, and tracheal cytotoxin.
There does not appear to be a zoonotic reservoir for B. pertussis—humans are its only host
.
The bacterium is spread by airborne droplets. The incubation period is 7–14 days.
(or whooping cough) is an infection of the respiratory system
and characterized by a “whooping” sound when the person breathes in. In the US it killed 5,000 to 10,000 people per year before a vaccine was available. Vaccination
has transformed this and between 1985-88 fewer than 100 children died from pertussis. Worldwide in 2000, according to the WHO, around 39 million people were infected annually and about 297,000 died. A graph is available showing the dramatic effect of introducing vaccination in England.
Bordetella pertussis infects its host by colonizing lung epithelial cells. The bacterium contains a surface protein, filamentous hemagglutinin, which binds to sulfatide
s that are found on cilia of epithelial cells. Once anchored, the bacterium produces tracheal cytotoxin, which stops the cilia from beating. This prevents the cilia from clearing debris from the lungs, so the body responds by sending the host into a coughing fit. These coughs expel some bacteria into the air, which are free to infect other hosts.
Bordetella pertussis has the ability to inhibit the function of the host's immune system. Two toxins, known as the pertussis toxin
(or PTx) and adenylate cyclase
(CyaA
), are responsible for this inhibition. CyaA converts ATP
to cyclic AMP, and PTx inhibits an intracellular protein that regulates this process. The end result is that phagocytes convert too much ATP to cyclic AMP, which can cause disturbances in cellular signaling mechanisms, and prevent phagocytes from correctly responding to an infection. PTx, formerly known as lymphocytosis-promoting factor, causes a decrease in the entry of lymphocytes into lymph nodes. This can lead to a condition known as lymphocytosis
, with a complete lymphocyte
count over of 4000/μL in adults or over 8000/μL in children.
The infection occurs most with children under the age of one when they are unimmunized
or children with faded immunity
, normally around the age 11 through 18. The signs and symptoms are similar to a common cold
: runny nose, sneezing, mild cough
, and low-grade fever
. The patient becomes most contagious during the catarrhal stage of infection, normally 2 weeks after the coughing begins. It may become airborne when the person coughs, sneezes, or laughs. Pertussis
vaccine
is part of the DTaP (diphtheria
, tetanus
, acellular pertussis
) immunization
. The paroxysmal cough precedes a crowing inspiratory sound characteristic of pertussis
. After a spell, the patient might make a “whooping” sound when breathing in, or vomit. Adults have milder symptoms, like prolonged coughing without the “whoop.” Infants less than 6 months may not have the typical whoop. A coughing spell may last a minute or more, producing cyanosis
, apnoea and seizures. However, when not in a coughing fit, the patient does not experience trouble breathing. This is because Bordetella pertussis inhibits the immune response and therefore very little mucus is generated in the lungs.
A prolonged cough may be irritating and sometimes a disabling cough may go undiagnosed in adults for many months.
laboratory for Gram stain (Gram negative, coccobacilli, diplococci arrangement), growth on Bordet-Gengou agar
or BCYE plate with added cephalosporin
to select for the organism, which shows mercury-drop-like colonies.
The organism is oxidase
positive, but urease
, nitrase, and citrate
negative. It is also non-motile.
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
, aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...
coccobacillus
Coccobacillus
A coccobacillus is a type of rod-shaped bacteria. The word coccobacillus reflects an intermediate shape between coccus and bacillus . Coccobacilli rods are so short and wide that they resemble cocci. Haemophilus influenzae and Chlamydia trachomatis are coccobacilli...
of the genus Bordetella
Bordetella
Bordetella is a genus of small , Gram-negative coccobacilli of the phylum proteobacteria. Bordetella species, with the exception of B. petrii, are obligate aerobes as well as highly fastidious, or difficult to culture. Three species are human pathogens ; one of these Bordetella is a genus of small...
, and the causative agent of pertussis
Pertussis
Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
or whooping cough. Unlike B. bronchiseptica
Bordetella bronchiseptica
Bordetella bronchiseptica is a small, gram-negative, rod-shaped bacterium of the genus Bordetella. It can cause infectious bronchitis, but rarely infects humans. Closely related to B. pertussis—the obligate human pathogen that causes pertussis or whooping cough—B...
, B. pertussis is non-motile. Its virulence factors include pertussis toxin, filamentous hæmagglutinin
Filamentous haemagglutinin adhesin
The filamentous hæmagglutinin adhesin is a large, filamentous protein that serves as a dominant attachment factor for adherence to host colliery epithelia cells of the respiratory tract. It is associated with biofilm formation and possesses at least four binding domains which can bind to...
, pertactin
Pertactin
Pertactin is a highly immunogenic virulence factor of Bordetella pertussis, a bacterium that causes pertussis. Specifically, it is an outer membrane protein that promotes adhesion to tracheal epithelial cells. PRN is purified from Bordetella pertussis and is used for the vaccine production as one...
, fimbria
Fimbria (bacteriology)
In bacteriology, a Cilli is a proteinaceous appendage in many Gram-negative and some Gram-positive bacteria that is thinner and shorter than a flagellum. This appendage ranges from 3-10 nanometers in diameter and can be up to several micrometers long...
, and tracheal cytotoxin.
There does not appear to be a zoonotic reservoir for B. pertussis—humans are its only 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...
.
The bacterium is spread by airborne droplets. The incubation period is 7–14 days.
Pertussis
PertussisPertussis
Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
(or whooping cough) is an infection of the respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
and characterized by a “whooping” sound when the person breathes in. In the US it killed 5,000 to 10,000 people per year before a vaccine was available. 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...
has transformed this and between 1985-88 fewer than 100 children died from pertussis. Worldwide in 2000, according to the WHO, around 39 million people were infected annually and about 297,000 died. A graph is available showing the dramatic effect of introducing vaccination in England.
Bordetella pertussis infects its host by colonizing lung epithelial cells. The bacterium contains a surface protein, filamentous hemagglutinin, which binds to sulfatide
Sulfatide
Sulfatides are a class of sulfated galactosylceramides synthesized primarily in the oligodendrocytes in the central nervous system. Sulfatides are a type of sulfolipid.-Clinical significance:...
s that are found on cilia of epithelial cells. Once anchored, the bacterium produces tracheal cytotoxin, which stops the cilia from beating. This prevents the cilia from clearing debris from the lungs, so the body responds by sending the host into a coughing fit. These coughs expel some bacteria into the air, which are free to infect other hosts.
Bordetella pertussis has the ability to inhibit the function of the host's immune system. Two toxins, known as the pertussis toxin
Pertussis toxin
Pertussis toxin is a protein-based AB5-type exotoxin produced by the bacterium Bordetella pertussis, which causes whooping cough. PT is involved in the colonization of the respiratory tract and the establishment of infection...
(or PTx) and adenylate cyclase
Adenylate cyclase
Adenylate cyclase is part of the G protein signalling cascade, which transmits chemical signals from outside the cell across the membrane to the inside of the cell ....
(CyaA
CyaA
Bifunctional hemolysin/adenylate cyclase is a protein that in B. pertussis is encoded by the cyaA gene. This protein in turn is cleaved into a calmodulin-sensitive adenylate cyclase and hemolysin. Both are virulence factors facilitating respiratory tract colonization by B. pertussis...
), are responsible for this inhibition. CyaA converts ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
to cyclic AMP, and PTx inhibits an intracellular protein that regulates this process. The end result is that phagocytes convert too much ATP to cyclic AMP, which can cause disturbances in cellular signaling mechanisms, and prevent phagocytes from correctly responding to an infection. PTx, formerly known as lymphocytosis-promoting factor, causes a decrease in the entry of lymphocytes into lymph nodes. This can lead to a condition known as lymphocytosis
Lymphocytosis
Lymphocytosis is an increase in the number or proportion of lymphocytes in the blood, usually detected when a complete blood count is routinely obtained. Lymphocytes normally represent 20 to 40% of circulating white blood cells...
, with a complete lymphocyte
Lymphocyte
A 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...
count over of 4000/μL in adults or over 8000/μL in children.
The infection occurs most with children under the age of one when they are unimmunized
Immunization
Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an agent ....
or children with faded immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
, normally around the age 11 through 18. The signs and symptoms are similar to a common cold
Common cold
The common cold is a viral infectious disease of the upper respiratory system, caused primarily by rhinoviruses and coronaviruses. Common symptoms include a cough, sore throat, runny nose, and fever...
: runny nose, sneezing, mild 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...
, and low-grade 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...
. The patient becomes most contagious during the catarrhal stage of infection, normally 2 weeks after the coughing begins. It may become airborne when the person coughs, sneezes, or laughs. Pertussis
Pertussis
Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
vaccine
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
is part of the DTaP (diphtheria
Diphtheria
Diphtheria is an upper respiratory tract illness caused by Corynebacterium diphtheriae, a facultative anaerobic, Gram-positive bacterium. It is characterized by sore throat, low fever, and an adherent membrane on the tonsils, pharynx, and/or nasal cavity...
, tetanus
Tetanus
Tetanus is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani...
, acellular pertussis
Pertussis
Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
) immunization
Immunization
Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an agent ....
. The paroxysmal cough precedes a crowing inspiratory sound characteristic of pertussis
Pertussis
Pertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
. After a spell, the patient might make a “whooping” sound when breathing in, or vomit. Adults have milder symptoms, like prolonged coughing without the “whoop.” Infants less than 6 months may not have the typical whoop. A coughing spell may last a minute or more, producing cyanosis
Cyanosis
Cyanosis 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...
, apnoea and seizures. However, when not in a coughing fit, the patient does not experience trouble breathing. This is because Bordetella pertussis inhibits the immune response and therefore very little mucus is generated in the lungs.
A prolonged cough may be irritating and sometimes a disabling cough may go undiagnosed in adults for many months.
Diagnosis
A nasopharyngeal or an oropharynx swab is sent to the bacteriologyBacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...
laboratory for Gram stain (Gram negative, coccobacilli, diplococci arrangement), growth on Bordet-Gengou agar
Bordet-Gengou agar
Bordet-Gengou agar is a type of agar plate optimized to isolate Bordetella, containing blood, potato extract, and glycerol, with an antibiotic such as cephalexin or penicillin and sometimes nicotinamide...
or BCYE plate with added cephalosporin
Cephalosporin
The cephalosporins are a class of β-lactam antibiotics originally derived from Acremonium, which was previously known as "Cephalosporium".Together with cephamycins they constitute a subgroup of β-lactam antibiotics called cephems.-Medical use:...
to select for the organism, which shows mercury-drop-like colonies.
The organism is oxidase
Oxidase test
The oxidase test is a test used in microbiology to determine if a bacterium produces certain cytochrome c oxidases. It uses disks impregnated with a reagent such as N,N,N′,N′-tetramethyl-p-phenylenediamine or N,N-Dimethyl-p-phenylenediamine , which is also a redox indicator...
positive, but urease
Rapid urease test
Rapid urease test, also known as the CLO test , is a rapid test for diagnosis of Helicobacter pylori. The basis of the test is the ability of H. pylori to secrete the urease enzyme, which catalyzes the conversion of urea to ammonia and bicarbonate.-Process:The test is performed at the time of...
, nitrase, and citrate
Citrate
A citrate can refer either to the conjugate base of citric acid, , or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.-Other citric acid ions:...
negative. It is also non-motile.
External links
- Pertussis Information from the World Health Organisation
- Bordetella chapter in Baron's Medical Microbiology (online text at the NCBINational Center for Biotechnology InformationThe National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...
bookshelf). - Bordetella pertussis in ARUP Consult — The Physician's Guide to Laboratory Test Selection and Interpretation
- Pertussis United Kingdom Health Protection Agency.