title: Association of complement sensitivity with virulence of Pasteurella multocida isolated from turkeys.
abstract: Two strains of Pasteurella multocida, both derivatives of strain P1059, were compared for virulence for 14-week-old turkeys and sensitivity to turkey plasma. Strain P1059-1, a nalidixic-acid-resistant mutant of P1059 with an LD50 of approximately 10(3) colony-forming units (CFU), was more resistant to the bactericidal effects of fresh turkey plasma at 37 C than avirulent strain P1059-1A. P1059-1A, with an LD50 of approximately 10(8) CFU, is an acapsular variant of P1059-1 that spontaneously arose after prolonged passage on artificial medium. The bactericidal effect on P1059-1A was removed when turkey plasma was treated with heat or with zymosan, maneuvers that removed hemolytic complement activity from turkey plasma.
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D001770:Blood Bactericidal Activity; D003165:Complement System Proteins / Q000276:immunology; D010325:Pasteurella / Q000276:immunology / Q000472:pathogenicity*; D010326:Pasteurella Infections / Q000276:immunology / Q000662:veterinary*; D011201:Poultry Diseases / Q000276:immunology*; D014422:Turkeys / Q000276:immunology* / Q000382:microbiology
chemical_list: D000907:Antibodies, Bacterial; D003165:Complement System Proteins