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Cell Wall Components and Antigenic Properties
B. pertussis is a Gram-negative bacterium that possesses lipo-polysaccharide (LPS) in the outer membrane. The LPS of B.pertussis is unusual. It is heterogenous with two distinct typesof LPSs, lipid A and lipid X. Both lipid A and lipid X can acti-vate the alternative pathway of complement and stimulate the release of cytokines. The role of their unusual LPS in the patho-genesis of whooping cough is unknown.
B. pertussis possesses two types of antigens. These are genus-specific somatic O antigen and strain-specific capsular K anti-gen. The O antigen is protein in nature, heat-stable, and is of single antigenic type. It is present in most of the strains of Bordetella. The K antigen is heat labile. These K antigens are ofdifferent types and are used for differentiating B. pertussis iso-lates in epidemiological studies.
A total of 14 agglutinating factors or agglutinogens have been identified based on agglutinin absorption test. B. pertus-sis strains are classified into various types based on the pres-ence of agglutinogens on their capsule. Factor 7 is found in all strains of B. pertussis (1–7, 13), B. parapertussis (7–10, 14), and B. bronchiseptica (7–13).
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