Characterisation of sucrose-negative Yersinia enterocolitica 4/O:3 isolates recovered from pig tonsils.

Sucrose-negative Yersinia enterocolitica isolates of bioserotype 4/O:3 have been recovered for the first time. They were found in 2% of the tonsils of clinically healthy fattening pigs. These sucrose-negative Y. enterocolitica isolates could not be differentiated from Y. kristensenii isolates using API 20E; thus, they were identified using PCR and sequencing. Using pulsed-field gel electrophoresis (PFGE). NotI profiles of sucrose-negative Y. enterocolitica 4/O:3 isolates showed a high similarity to sucrose-positive Y. enterocolitica 4/O:3 isolates. This study demonstrated that sucrose-negative Y. enterocolitica 4/O:3 isolates of porcine origin can harbour virulence genes; plasmid-encoded virulence markers were found in 8 out of 11 isolates and all isolates contained chromosomal-encoded virulence markers. Thus, the pathogenicity of sucrose-negative Yersinia isolates should always be assessed.