Antimicrobial Resistance, Virulence, and Genotypic Profile Comparison of Campylobacter jejuni and Campylobacter coli Isolated from Humans and Retail Meats

A total of 360 spatially and temporally related Campylobacter isolates, including 168 from clinical human cases (Campylobacter jejuni n = 148; Campylobacter coli n = 20) and 192 from retail meats (C. jejuni n = 114; C. coli n = 78), were analyzed for antimicrobial susceptibilities, virulence, and genotypic profiles. Ciprofloxacin-resistant C. jejuni was observed in 13.5% and 19% of the isolates from humans and retail chicken breasts, respectively. Antimicrobial resistance to ciprofloxacin and erythromycin was detected in C. coli isolates recovered from 29% and 16.6% of retail meats and 15% and 5% humans, respectively. Overall, virulence determinants were more prevalent in Campylobacter isolates recovered from retail meats than from humans. C. jejuni isolates from humans were significantly associated with the rakR, dnaJ, and pld genes, whereas C. coli isolates from retail meats were associated with the dnaJ, pld, and virB11 virulence genes. Genotyping of 262 C. jejuni isolates using pulsed-field gel electrophoresis revealed a total of 186 unique SmaI patterns, with 14% of patterns composed of isolates recovered from retail meats and ill humans. All unique groups with indistinguishable SmaI patterns were further analyzed by a second restriction enzyme (KpnI), which revealed limited overlap between isolates from different sources. Significant association between doxycycline-resistant C. jejuni strains recovered from humans and different virulence genes (e.g., cdtB) was identified at the statistical level but not at the genotypic level. In conclusion, significant differences observed in the distribution of antimicrobial resistance profiles, virulence determinants, and genotypic diversity among C. jejuni and C. coli isolates indicate that there are sources other than retail meats that may also contribute to human Campylobacter infections.