Bordetella pertussis is the name for a bacterium. It is considered the causative agent of whooping cough.
What is bordetella pertussis?
Bordetella pertussis is a species of bacteria that belongs to the genus Bordetella. The gram-negative small bacterium causes whooping cough (pertussis) and presents singly or in pairs. The name Bordetella goes back to the Belgian bacteriologist Jules Baptiste Bordet (1870-1961), who isolated the germ together with a colleague in 1906. This laid the foundation for the pertussis vaccine, which was used from 1933. Humans serve as the sole reservoir for Bordetella pertussis. On average, the bacterium causes about 17 million cases of pertussis per year around the world. About 90 percent of cases are recorded in developing countries.
Occurrence, distribution, and characteristics
Bordetella pertussis exhibits the shape of a rod. In addition, the aerobic immobile germ produces various proteins. Their toxins are partly responsible for the symptoms of pertussis. The pathogens can attach well to the respiratory mucosa, where they multiply. From the taxonomic point of view, the Bordetellae belong to the Alcaligenaceae family. Their organism can be grown on blood agar, charcoal blood agar, Bordet-Gengou blood agar as well as various synthetic culture media. The growth of Bordetella pertussis bacteria progresses slowly. Thus, it takes between three and six days for the colonies, which are the size of a pinhead, to grow. Bordetella pertussis colonizes the cilia of the respiratory epithelium. The growth of the bacteria is affected by pertussis toxin (PTx) and filamentous hemagglutinin. PTx is understood to be an exotoxin. It occurs both in the extracellular fluid and cell-bound. The exotoxin is composed of an A-component and a B-component. The A-component is ADP-ribosyl transferase, while the B-component consists of five polypeptide subunits. These bind to the carbohydrate structures located on the surface of the cells. PTx has the property of limiting the activity of phagocytes, special immune cells. It also triggers systemic effects. These include greater sensitivity to histamine, an increase in insulin production, and lymphocytosis. Apart from the pertussis toxin, other toxins are produced by the bordetelles. These ensure a more rapid spread of the pathogen within the human body. Foremost among these is the tracheal cytotoxin, which is responsible for restricting the cilia beat in the respiratory tract. Bordetella pertussis is equipped with hair-like structures on its surface called pili. The pili ensure that the bordetella can attach to the mucosa of the respiratory tract in humans. Furthermore, the surface of Bordetella pertussis has some outer membrane proteins, lipopolysaccharides as well as fimbriae. Bordetellae proliferate on the ciliary epithelium of the respiratory mucosa, resulting in local destruction of the mucosa. Bordetella pertussis occurs throughout the year. Its spread is even more pronounced in the cool autumn and winter months. In Germany, the germs are mainly found in younger children. Babies are also at high risk of being infected with bordetella. But adults can also be infected with Bordetella pertussis. Bordetella pertussis is considered highly contagious. The bacteria are transmitted by droplet infection. In most cases, there is close contact with the infected person and the bordetella gets into the body of another person through sneezing, coughing or talking. The incubation period is usually 9 to 20 days.
Diseases and symptoms
The bacterium Bordetella pertussis causes whooping cough. This disease initially causes typical cold symptoms. These include a cold, cough, and some fever. The symptoms sometimes last up to 14 days. The first stage of the disease is called the catarrhal stage by physicians. During this stage, there is the greatest risk of infection. As the disease progresses, the cough becomes more and more intense. This second stage is called stage convulsivum and is characterized by coughing fits.The cough bursts appear staccato and are conspicuous by a protruding tongue. It is not uncommon for patients to regurgitate mucus with a glassy consistency. In some cases, the patients also suffer from vomiting. The coughing fits are often numerous, especially during the night hours. Sometimes they are also caused by physical exertion. Overall, the duration of the convulsivum stage is from two to six weeks. The last stage of whooping cough caused by bordetella is called stage decrementi. The number of coughing attacks gradually decreases. The same applies to their extent. This stage takes about three to six weeks. If antibiotics are not administered, it can also last six to ten weeks. There is a risk that Bordetella pertussis may cause complications of whooping cough. These are mostly middle ear infections or pneumonia. These result from secondary infections with pneumococci or Haemophilus influenzae. Another relatively common complication is seizures. Treatment with antibiotics is often of limited efficacy in Bordetella pertussis, unlike other bacterial species. Thus, the coughing attacks result from the toxins produced by the germs. To be effective, antibiotics must be administered at the catarrhal stage, or at the latest in the early convulsive stage. Vaccination is considered the best way to prevent Bordetella pertussis infection. For this purpose, the patient first receives basic immunization with several rounds of vaccination.