Erythromycin-resistant Campylobacter coli from slaughtered animals as a potential public health risk

Erythromycin-resistant Campylobacter were isolated from pig, cattle, and poultry carcasses slaughtered in Poland between 2008 and 2011. A total of 1335 strains were examined and among them 20 (1.5%) showed a high level of erythromycin resistance (≥ 32 mg/l) as determined by the microbroth dilution method. All these isolates were C. coli and mainly originated from poultry (15 strains). PCR amplification or DNA sequencing identified the mutation A2075G in the 23S rRNA gene in all strains tested. The vast majority of such C. coli were also resistant to quinolones, tetracyclines, and streptomycin whereas none of them revealed resistance to gentamycin. Furthermore, several isolates (14; 70.0%) displayed multi-resistance pattern against quinolones, aminoglycosides, and tetracyclines. PCR analysis identified several putative virulence genes such as cadF, flaA, and iam (present in all erythromycin resistant isolates) as well as the cdtA and flhA markers (19 and 16 strains, respectively) among C. coli tested. On the other hand, only two out of 20 isolates were positive for the ciaB and docA genes. Furthermore, none of the analysed strains had the virB11 and wlaN markers. A molecular relationship determination of the erythromycin-resistant C. coli performed by pulsed field gel electrophoresis (PFGE) revealed 17 different types. This reflects the high genetic diversity among the examined isolates. The results obtained suggest that erythromycin-resistant C. coli from food-producing animals may represent an underestimated potential health risk for consumers.