Bordetella

Bordetella is a genus of small (0.2-0.7µm), Gram-negative coccobacilli of the phylum Proteobacteria. Bordetella species, with the exception of B. petrii, are obligate aerobes, highly fastidious, and difficult to culture. All of the Bordetella species can infect humans. B. pertussis and occasionally B. parapertussis cause pertussis or whooping cough in humans, and some B. parapertussis strains can colonize sheep. Transmission occurs by direct contact, or via respiratory aerosol droplets, or fomites. Bacteria initially adhere to ciliated epithelial cells in the nasopharynx, and this interaction with epithelial cells is mediated by a series of protein adhesions. The initial catarrhal phase of infection features symptoms similar to those of the common cold, and during this period, large numbers of bacteria can be recovered from the pharynx. Thereafter, the bacteria proliferate and spread further into the respiratory tract, where the secretion of toxins gives rise to ciliostasis and facilitates the entry of bacteria into tracheal/bronchial ciliated cells.