Bordetella pertussis

It is the causative agent of pertussis. Morphologically it is Gram negative coccobacilli, non motile and some strains are encapsulated. Colonies in culture have shiny, confluent appearance hence they are described as “aluminium paint”, “bisected pearls”, “mercury drops”, or “thumbprint appearance”.

Tracheal cytotoxin leads to damage of ciliated respiratory epithelium and release of nitric oxide further adding to the damage. Pertussis toxin causes rise in cAMP by inhibiting Gi protein. It also causes lymphocytosis. The disease presents as an upper respiratory infection followed by paroxysmal or “whooping” cough in children. In adults it is less severe presenting as a low level chronic dry cough. Such adults are still infectious to susceptible children. Identification is done by fluorescent staining and PCR of samples from nasopharyngeal swabs, culture on Bordet Gengou medium, antibody detection by agglutination, indirect haemagglutination, complement fixation and ELISA.