Bordetella is a genus of small (0.2 - 0.7 µm), Gram-negative coccobacilli of the phylum proteobacteria. Bordetella species are strict aerobes as well as highly fastidious. Three species are human pathogens (B. pertussis, B. parapertussis, B. bronchiseptica); one of these (B. bronchiseptica) is also motile.