B. pertussis is a very small, prokaryotic, coccoid bacterium, which does not make endospores. It is a gram negative bacterium which means the cell structure contains an outer membrane, an inner membrane, and a thin peptidoglycan layer. It metabolizes through aerobic respiration, is nonmotile and an encapsulated microorganism. It appears either in pairs or singly, cannot survive in the environment and only reside in human hosts, where it usually appears in the trachea and the bronchi. B. pertussis produces several virulence factors. These include pertussis toxin, which is secreted in the cell and extracellular fluid, and filamentous hemagglutinin, which is a “fimbrial-like structure on the bacterial surface” (Todar).
B. pertussis is nutritionally fastidious meaning it has complex growing requirements, and is difficult to grow without specialized media. It requires special growth factors and may not grow on routine media, although it has been found that the organism grows better on a media that has a slightly acidic pH. Growth of this organism is restrained by its own waste as well as heavy metals, peroxides, sulfides, and fatty acids. To neutralize any inhibitory substances and absorb toxic metabolites this organism is often grown on media with rich concentrations of blood, or charcoal. ("Pertussis."). Two different solid cultures that are used in growing B. pertussis are Bordet-Gengou agar (BGA) and Regan-Lowe agar (RLA). Bordet- Gengou agar contains potato starch and is peptone free, also an inhibitory substance. It also contains glycerol as a stabilizer, and an
antibiotic, such as penicillin, to restrain gram positive organisms from growing, although the antibiotic may slightly