Antimicrobial susceptibility of Yersinia enterocolitica strains isolated from pigs in the north-eastern region of Poland

The purpose of the study was to evaluate the susceptibility of Yersinia (Y.) enterocolitica strains isolated from pigs in the north-eastern region of Poland to various chemotherapeutics. In total, the study comprised 103 Y. enterocolitica strains isolated in the years 2000-2007 from pig farms located in north-eastern Poland. The in vitro susceptibility of Y. enterocolitica strains to 14 chemotherapeutics was evaluated (ciprofloxacin, enrofloxacin, norfloxacin, gentamycin, neomycin, streptomycin, oxytetracycline, tetracycline, chloramphenicol, colistin, tiamulin, sulphonamides, sulphamethoxazole/trimethoprim-SXT, nitrofurantoin). Commercially available antimicrobial disks produced by Rosco and OXOID were used. The in vitro susceptibility of Y. enterocolitica strains was evaluated by a standardized disk diffusion method using Mueller-Hinton agar, according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. The study demonstrated the significant variation in the susceptibility of the isolates. The Y. enterocolitica strains were found to show the highest in vitro susceptibility to quinolones (ciprofloxacin, norfloxacin, enrofloxacin), gentamycin and colistin. A slightly lower susceptibility in case of chloramphenicol and SXT was noticed. Streptomycin and neomycin were less effective. Sulfonamides and nitrofurantoin were also found to have very limited efficacy. However, Y. enterocolitica strains were fully resistant to tiamulin. Taking into account the widespread presence of Y. enterocolitica in many animal species and their increasing risk for public health, it is necessary to continually monitor the susceptibility of Y. enterocolitica strains to chemotherapeutics.