Bordetella pertussis is a slow-growing organism that requires specialized conditions for growth. It is the most fastidious species within the genus. One of the media used for its cultivation is charcoal agar supplemented with 10% horse (or sheep) blood and cefalexin. Plates are incubated in air without elevated carbon dioxide at 35°C for a minimum of 7 days before being reported as negative (most isolates are detected in 3 to 4 days). Colonies are small, shiny and round. With age they become whitish grey. Repeated subculture of B.pertussis leads to loss of fastidiousness and laboratory adaptation to a variety of media.
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. There does not appear to be a zoonotic reservoir for B. pertussis - humans are its only host. The bacterium is spread by coughing and by nasal dripping. The incubation period is 7-14 days.
Pertussis (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. Worldwide in 2004, around 18 million people were infected  and about 254,000 died .
Bordetella pertussis infects its host by colonizing lung epithelial cells. The bacterium contains a surface protein, filamentous hemagglutinin, which binds to sulfatides 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.
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.
Bordetella pertussis basic characteristics
- SHORT GRAM-NEGATIVE RODS or COCCOBACILLI
- CATALASE: POSITIVE
- OXIDASE: POSITIVE
- OBLIGATE AEROBES
Identification of Bordetella pertussis
- Slow growth on selective media for pathogenic bordetellae
- Growth on blood agar: fresh clinical isolates will not grow on common blood or chocolate agar
- Do not use carbohydrates as an energy source
- Serologic identification (agglutination in a polyclonal antiserum specific for B.pertussis or the fluorescein-labeled-antibody procedure)
Antibiotic treatment of pertussis
Bordetella pertussis on charcoal-blood agar with cefalexin
Bordetella pertussis Gram stain
CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC)
- Bordetella pertussis (VPD Surveillance Manual, 2015)
- Bordetella pertussis (VPD Surveillance Manual, 2015); pdf
- Pertussis (Whooping Cough); specimen collection
- Identification of Bordetella species
UK Standards for Microbiology Investigations