Antibiotic Resistance and Β-lactamases of Yersinia Enterocolitica Isolated from Pigs in Poland

Sixty-two isolates of pig-derived Yersinia enterocolitica belonging to 1A and 4 biotypes and non-typeable isolates were subjected to antimicrobial resistance testing by the disc diffusion method. The presence of β-lactamase A (Bla-A) and B (Bla-B) was detected by the double disc diffusion test, and the β-lactamase genes blaA and blaB in these isolates were detected by PCR. The isolates were resistant or moderately susceptible mostly to penicillins (except piperacillin) and first-generation cephalosporins. The majority of the isolates of biotype 1A were resistant or moderately susceptible to amoxicillin/clavulanic acid. Three isolates of biotype 4 were also resistant to amoxicillin/clavulanic acid. Most of Y. enterocolitica isolates were resistant or intermediately susceptible to second-generation cephalosporins. Cefotaxime was the most active third-generation cefalosporin against the tested Y. enterocolitica. No isolate was resistant to imipenem. Tetracyclines, aminoglycosides, and quinolones showed high activity against Y. enterocolitica. The presence of the Bla-A enzyme was found in 27/31 isolates of biotype 1A, 22/28 isolates of biotype 4, and in all untypeable isolates. In these isolates the blaA gene was detected by PCR amplification. In all Y. enterocolitica isolates blaB gene was detected but not all isolates of biotype 4 showed the presence of Bla-B.