Molecular characterization and genotypic antimicrobial resistance analysis of Campylobacter jejuni and Campylobacter coli isolated from broiler flocks in Northern Italy

Genetic variability and genotypic antimicrobial resistance (AMR) of Campylobacter jejuni and Campylobacter coli from commercial broiler farms were investigated in this study. Campylobacter isolates were genetically characterized by RAPD-PCR and flaA- and flaB-SVR sequence-based typing. Eight RAPD types were identified in C. jejuni and 3 in C. coli, while 16 fla profiles were detected among all isolates. Further, 13 flaA-SVR and 13 flaB-SVR alleles were identified. Both typing methods detected a high level of genetic diversity, but fla-SVR typing showed a higher discriminatory power. Indeed, Simpson’s index of fla typing (D = 0.920) was higher than that of RAPD typing (D = 0.814). Moreover, the association of flaA- and flaB-SVR sequence analysis showed a higher discriminatory power compared to the sequence analysis of single loci. Isolates were also analyzed by the MAMA-PCR test and the detection of cmeB gene to determine the occurrence of genetic determinants of AMR to macrolides and fluoroquinolones (FQs) and multidrug-resistance (MDR). The A2074C and A2075G mutations in the 23S rRNA gene, the C257T mutation in the gyrA gene, and the cmeB gene were higher in C. coli (19.0%, 67.0%, 100.0% and 100.0%, respectively) than in C. jejuni (0.0%, 3.1%, 48.3% and 48.3%, respectively). This study showed a high degree of genetic diversity and a high prevalence of genetic determinants of macrolide-, FQ-, and multidrug-resistance among C. jejuni and C. coli isolates from Italian commercial broiler farms.