Campylobacter spp. - prevalence on pig livers and antimicrobial susceptibility

The objective of the study was to determine the prevalence of Campylobacter spp. on surfaces of slaughtered pig livers. Multilocus sequence typing (MLST) was performed to determine the sequence types (STs) of selected Campylobacter coli isolates. Additionally, C. coli and Campylobacter jejuni isolates were tested for antimicrobial susceptibility by the broth dilution method. The minimal inhibitory concentrations were determined for erythromycin, gentamicin, ampicillin, ampicillin/sulbactam, nalidixic acid, ciprofloxacin, tetracycline and trimethoprim/sulphamethoxazole. Samples were taken during the slaughtering process in a slaughterhouse in Lower Saxony, Germany. Altogether, 10% of 1500 surfaces of pig livers from 50 fattening herds was found to be Campylobacter positive, with C. coli as the predominant species (76%) followed by C. jejuni (21%). Resistance to erythromycin and tetracycline was higher in C. jejuni compared to C. coli, whereas C. coli were more resistant to quinolone compared to C. jejuni. Fluoroquinolone resistance is usually associated with cross-resistance to quinolone, but in the presented investigation C. coli as well as C. jejuni showed a higher resistance to ciprofloxacin (28.6% and 20.0%, respectively) than to nalidixic acid (9.5% and 0%, respectively). A high genetic diversity of the C. coli isolates was demonstrated by MLST. Differences in STs and antimicrobial resistance pattern indicate that the Campylobacter strains originated from the pig itself and not from the slaughterhouse. A comparison of the STs with those reported in the C. jejuni/coli PubMLST database showed an overlap of porcine and human isolates, indicating that C. coli isolates from pigs should be considered as potential sources of human infection.