Introduction
Bordetella is a genus of small (0.2 – 0.7 µm), Gram-negative coccobacilli of the phylum Proteobacteria. Bordetella species, with the exception of B. petrii, are obligate aerobes, as well as highly fastidious, or difficult to culture. The Bordetella genus is named after Jules Bordet. All species can infect humans. The first three species to be described (B. pertussis, B. parapertussis, B. bronchiseptica), are sometimes referred to as the 'classical species'. 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 adhesins. These include filamentous haemaglutinin, pertactin, fimbriae, and pertussis toxin (though expression of pertussis toxin is unique to B. pertussis). As well as assisting in adherence to epithelial cells, some of these are also involved in attachment to immune effector cells.