Isolation, characterization and antimicrobial resistance of Yersinia enterocolitica from Polish cattle and their carcasses

Abstract

Background: Yersinia enterocolitica is a heterogeneous bacterial species that has been divided into six biotypes and more than 70 serotypes. Each year, the European Food Safety Authority classifies yersiniosis caused by Y. enterocolitica as one of the most important zoonotic diseases. The prevalence of Y. enterocolitica in cattle has not been thoroughly analyzed in Poland, and beef and bovine carcasses contaminated with antimicrobial resistant Y. enterocolitica pose a health risk for both, farm workers and consumers. Therefore, the aim of this study was to evaluate the prevalence of Y. enterocolitica in cattle and to determine the antimicrobial susceptibility of the isolated strains.

Results: A total of 1020 samples were analyzed, including 660 rectal swabs collected from live cattle and 360 swabs from cold-stored beef carcasses. The results of this study indicate that Y. enterocolitica was isolated from three of the 15 examined cattle herds and the prevalence within these herds ranged from 0% to nearly 32%. Y. enterocolitica was isolated from 14.7% of the examined heifers, 7.4% of calves and 5.5% of adult cows. More than 65% of the strains were isolated from cold enrichment. The strains isolated from live cattle tested positive for the ystB gene, while ail and ystA genes were not found. Most of the isolated strains belonged to bioserotype 1A/NT. The majority of the isolated strains were resistant to ampicillin, cefalexin and amoxicillin with clavulanic acid, however these are expected phenotypes for Y. enterocolitica.

Conclusions: The results of this study indicate that Y. enterocolitica is present in cattle herds in Poland. The strains isolated from live cattle were ystB-positive, most of them belonged to bioserotype 1A/NT. The prevalence of Y. enterocolitica strains was generally low in cold-stored beef carcasses.

Keywords: Antimicrobial susceptibility; Bioserotyping; Cattle; Cold-stored beef carcasses; Molecular characterization; Multidrug resistance; Prevalence; Yersinia enterocolitica.

Fig. 1

Isolation of Y. enterocolitica strains from cattle in herds No. 1, No. 2 and No. 5. The number of Y. enterocolitica strains isolated from different age groups of animals compared to the total number of animals in three herds where Y. enterocolitica was detected: A – herd No. 1; B – herd No. 2; C – herd No. 5

Fig. 2

Isolation of Y. enterocolitica strains from cattle in the analyzed herds. The number of Y. enterocolitica strains isolated from animals belonging to the analyzed herds compared to the total number of animals in these herds

Fig. 3

Analysis of SNPs of the ystB gene in Y. enterocolitica strains. Each line corresponds to a different nucleotide sequence of the ystB gene and is marked with a different color. The nucleotide sequences were compared with the reference sequences – the closer the lines, the greater the similarity between the compared sequences. Variations were defined as sequences not showing 100% homology with the reference sequences

Fig. 4

Phylogenetic analysis of Y. enterocolitica strains isolated from cattle. The evolutionary history was inferred using the UPGMA method. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site. The analysis involved 17 nucleotide sequences. Codon positions included were 1st + 2nd + 3rd + Noncoding. All positions containing gaps and missing data were eliminated. There were a total of 253 positions in the final dataset. Evolutionary analyses were conducted in MEGA5

Fig. 5

Antimicrobial susceptibility of Y. enterocolitica strains isolated from cattle. The number of Y. enterocolitica strains resistant/intermediate resistant/susceptible to 13 examined antimicrobials