Relationships between virulence and morphological or serological properties of variants dissociated from serotype 1 Haemophilus paragallinarum strains.
Relationships between morphological or serological properties and virulence were investigated in seven Haemophilus paragallinarum variants. The variants, originated from five serotype 1 strains, were classified into seven types on the basis of colony morphology and iridescence and the presence of variant-specific antigens. Smooth (S) and encapsulated organisms having variant-specific antigens and forming highly iridescent (ir+) colonies were highly virulent in vivo; slightly encapsulated organisms having variant-specific antigens and forming slightly iridescent (ir +/-) colonies were moderately virulent; and nonencapsulated or slightly encapsulated organisms with or without variant-specific antigens and forming noniridescent (ir-) or ir +/- colonies were avirulent. Virulence was well correlated with the amount of capsule substance containing hyaluronic acid. The evidence suggests that the presence of variant-specific agglutinogen L and hemagglutinin HA-L seem to be responsible for adherence or colonization, but not for virulence, of the organisms in chickens.
D000818:Animals; D000942:Antigens, Bacterial / Q000032:analysis; D002645:Chickens; D014644:Genetic Variation; D006190:Haemophilus / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D014774:Virulence
D000942:Antigens, Bacterial