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Isolation of an Atypical Strain of Actinobacillus pleuropneumoniae Serotype 1 with a Truncated Lipopolysaccharide Outer Core and No O-Antigen

2005; American Society for Microbiology; Volume: 43; Issue: 7 Linguagem: Inglês

10.1128/jcm.43.7.3522-3525.2005

1098-660X

Mario Jacques, Josée Labrie, Frank St. Michael, Andrew D. Cox, Marie-Anne Paradis, C. P. Dick, Christian Klopfenstein, André Broes, Nahuel Fittipaldi, Marcelo Gottschalk,

Aquaculture disease management and microbiota

ABSTRACT 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.