Detection and Characterization of Thermotolerant Campylobacter Resistant to Antibiotics of Priority Use in Humans Present in Broiler Slaughterhouses and Retail Markets

<b>Background</b>: This study aimed to assess the presence of thermotolerant <i>Campylobacter</i> resistant to ciprofloxacin and erythromycin in poultry slaughterhouses and retail markets, as well as to characterize their multidrug resistance profiles, genetic determinants, and clonal relationships. <b>Methods</b>: Samples were collected at slaughterhouses from cecal content (n = 270), neck skin (n = 270), and wastewater (n = 9), and at retail markets from breast skin (n = 241). Isolates were obtained from mCCDA agar supplemented with ciprofloxacin (2 μg/mL) and identified as <i>C. jejuni</i> or <i>C. coli</i> by PCR. The agar microdilution test was used to determine the minimum inhibitory concentration for ciprofloxacin and erythromycin, and other critical antibiotics. Point mutations in <i>gyrA</i> (Thr86Ile) and 23S rRNA (A2075G), virulence genes (<i>flaA</i>, <i>flhA</i>, <i>cadF</i>, and <i>cdt</i>), and clonal relationships were assessed by PCR and PFGE. <b>Results</b>: At the slaughterhouses, thermotolerant <i>Campylobacter</i> spp. resistant to erythromycin and ciprofloxacin were detected in 48.55% (107/549) of the samples, whereas 4.56% (11/241) of retail samples were positive. The Thr86Ile substitution in <i>gyrA</i> and the A2075G mutation in the 23S rRNA gene were detected in 92.97% and 89.84% of the isolates, respectively. Most isolates (>80%) were multidrug resistant and harbored key virulence genes (<i>flaA</i>, <i>flhA</i>, and <i>cadF</i>). <i>C. jejuni</i> exhibited the highest prevalence of <i>cdt</i> genes (76.19%). There was substantial genotypic diversity among isolates, with broad distribution across the sampled matrices and sites. <b>Conclusions</b>: These findings highlight the circulation of multidrug-resistant and potentially virulent thermotolerant <i>Campylobacter</i> spp. in the later stages of the poultry meat supply chain.