Isolation of an atypical strain of Actinobacillus pleuropneumoniae serotype 1 with a truncated lipopolysaccharide outer core and no O-antigen.
A field isolate of Actinobacillus pleuropneumoniae, the causative agent of porcine fibrinohemorrhagic necrotizing pleuropneumonia, was sent to the diagnostic laboratory for serotyping. The isolate presented a clear reaction, with both polyclonal antibodies against serotype 1 and monoclonal antibodies against the capsular polysaccharide of serotype 1. It also exhibited a PCR profile of Apx toxins expected for serotype 1. The isolate, however, failed to react with monoclonal antibodies against the O-antigen of serotype 1 lipopolysaccharide (LPS), suggesting a rough phenotype. The lipid A-core region of the isolate migrated faster than the corresponding region of the serotype 1 reference strain S4074 by Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting the presence of a truncated core. Sugar analysis and mass spectrometry analysis of the O-deacylated LPS from the field isolate were consistent with the absence of O-antigen and truncation of the outer core compared to the wild-type reference strain. Experimental infection of pigs confirmed the virulence of the isolate. This is the first report of an isolate of A. pleuropneumoniae serotype 1 with a truncated outer core and a rough LPS phenotype. Veterinary diagnostic laboratories should be vigilant, since infections caused by such an isolate will not be detected by serological tests based on LPS O-antigen.
Jacques
Mario
M
Groupe de recherche sur les maladies infectieuses du porc, Faculté de médecine vétérinaire, Université de Montréal, 3200 rue Sicotte, C.P. 5000, St-Hyacinthe, Québec, Canada J2S 7C6. mario.jacques@umontreal.ca
Labrie
Josée
J
St Michael
Frank
F
Cox
Andrew D
AD
Paradis
Marie-Anne
MA
Dick
C Paul
CP
Klopfenstein
Christian
C
Broes
André
A
Fittipaldi
Nahuel
N
Gottschalk
Marcelo
M
D000189:Actinobacillus Infections / Q000382:microbiology / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D019081:O Antigens; D010641:Phenotype; D012703:Serotyping; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D014774:Virulence
D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D019081:O Antigens