The germ Bordetella parapertussis belongs to the genus Bordetella and is difficult to distinguish from the related germ Bordetella pertussis.
What is Bordetella parapertussis?
The bacterium Bordetella parapertussis owes its name to its genetic and biochemical similarity to the related germ Bordetella pertussis. The generic name Bordetella was used in memory of the microbiologist Jules Bordet. The germ has a short and coccoid rod shape. It is approximately 400 nanometers wide and 800 nanometers long and is non-motile. It is gram-negative and thus has only a murein envelope with an overlying lipid layer. Bordetella parapertussis has an aerobic metabolism and is incapable of replication without oxygen. Thus, the metabolism of the germ is based on respiration. Pili, also called fimbriae, are deposited on the bacterial envelope. Pili are burr-like branchings that allow the bacterium to adhere to various surfaces. Endospores are not formed by the germ. Transmission occurs only via droplet infection by means of expectorated secretions during coughing. Amino acids, which are obtained by chemoorganotrophic specialization, are needed to build up the cell’s own substances and as a source of energy. Citrate and puyruvate can also be absorbed. The germ cannot utilize sugars and is therefore asaccharolytic. Sodium chloride and bile salts are tolerated by the germ in small amounts. Enrichment of the culture media with 3% sodium chloride shows no effect on replication of the pathogen. Higher levels may block auto-replication. A bile salt content of up to 10% is tolerated without problems. At a level of 40%, replication is completely blocked. A complete sequencing of the genome of the species Bordetella parapertussis was already carried out in 2003. A strain isolated from a child in 1993 was used for this purpose. The size of the genome, 4774 kilobase pairs, is roughly comparable to the size of the genome of the bacterial species Escherichia coli. Sequencing of two other strains was performed by 2013. Strain Bpp5, isolated from a sheep, was the first to identify a plasmid of unknown utility in the germ.
Occurrence, distribution, and properties
Bordetella parapertussis colonizes only the epithelial cells of the respiratory tract. This is that tract that houses the respiratory tract and thus allows oxygen uptake. The bacterium only has the opportunity to open up new hosts via droplet infection. Optimal conditions are created in the oxygen-rich respiratory tract for the germ’s metabolism, which is based on aerobic processes.
Diseases and ailments
Bordetella parapertussis and Bordetella pertussis are typical triggers of whooping cough. The germs trigger a moderate form of whooping cough and are responsible for 5-20% of the cases registered annually. The possibility of a really severe disease with lethal consequences exists in children up to the age of six. Due to the high risk of infection, mandatory reporting of the disease was introduced in 2013. Classic whooping cough is divided into three stages, but atypical and persistent courses can also occur in infected persons of all ages. After an incubation period of approximately 7-14 days, the catarrhal stage sets in. It is characterized by flu-like symptoms, mild fever and a non-productive irritable cough. The catarrhal stage lasts about two weeks, and infection via droplet infection is most likely. In the second stage, the convulsive stage, the typical symptoms of whooping cough appear. Dense successive coughing attacks with deep mucous sound, often with tongue sticking out and glassy sputum are present. Furthermore, there is retching, which can lead to vomiting. After the coughing attack, there is often a strong lung whooping, which may also be heard in a diminished form during the infected person’s normal breathing. The convulsivum stage is the longest stage of whooping cough and may last from two to six weeks. The third stage, the decrementi stage, refers to the slow resolution of the disease. The coughing attacks decrease and the deep and mucous sound recedes. Overall, the sufferer finds it much easier to cough.Strangles and mucous sputum no longer occur to the same extent and the overall appearance of the disease slowly flattens out. Since the lipopolysaccharides typical of gram-negative germs are stored on the cell wall and generate antibodies, an infection can be traced via these antibodies. Differentiation between the species Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica can also be made by the antibodies, since the lipopolysaccharides (LPS) of the individual species differ. The proteins of the outer membrane and the fimbriae offer themselves as further antigens (antibody generators). The proteins trigger agglutination (agglutination) when encountering the corresponding antibodies. A biochemical differentiation of the germs relevant to human medicine is difficult. However, the serological detection of the corresponding immunoglobulins (antibodies) offers the possibility to identify the exact type of Bordetella germ. Unfortunately, this differentiation is not possible in the early stages of the infection, since the corresponding antibodies are not yet formed. The situation is further complicated by the fact that active immunoglobulins can be confused with immunoglobulins from a previous infection or vaccination. An uncertain diagnosis can be remedied by a subsequent polymerase chain reaction (PCR). For this purpose, gene segments present in swabs taken from the patient are amplified. These can subsequently provide confirmation of the suspicion. Another problem with Bordetella germs in PCR is the genetic similarity of parapertussis and pertussis. Gene sequences that are characteristic of the individual bacterial strains are very difficult to identify. Advanced testing methods to improve PCR, such as fluorescent light to better identify gene sequences, are part of modern research. Elevated titers in combination with a positive PCR test provide at least a very high probability that it is the Bordetella species detected.
