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The Microorganism
Bordetella pertussis is responsible for the disease known as "Whooping Cough." B. pertussis is a small, gram-negative bacteria that colonizes the upper respiratory tract of primates and humans. There is no other known natural reservoir for this bacterium. B. pertussis is known to be fastidious and needs very specific conditions in order to grow. Even given these conditions, its replication is generally quite slow.
Bordetella pertussis contains a lipopolysaccharide endotoxin in its outer surface. This LPS is heterogenous, consisting of two major forms (Lipid-A and Lipid-X) that differ in their phosphate content.
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| Image courtesy of The Univeristy of Wisconsin, Madison http://www.bact.wisc.edu/Bact330/B.pertussis.jpeg |
Virulence factors are regulated by the bvg operon. Phase variation allows the loss of most virulance factors as well as some outer membrane proteins. Phenotypic modulation occurs in response to environmental cues and is reversible. BvgA and BvgS are members of a family of signal-transducing proteins that communicate via a four-step His-Asp-His-Asp phosphorelay.
Strains of Bordetella pertussis found in different parts of the world (e.g. Canada, the Netherlands) have been found to differ from each other and from whole-cell vaccine strains.