WGS-based surveillance for Campylobacter spp. in human infections and chicken meat production in Italy (2023)

Campylobacter spp. infections present an urgent and significant global public health challenge. This study offers a genomic characterization of Campylobacter spp. isolates from human samples and chicken-origin food sources in Italy during 2023. Whole-genome sequencing, cluster analysis, genomic comparison of human and food of animal origin isolates, and characterization of antimicrobial resistance mechanisms were performed on 257 isolates. Campylobacter jejuni revealed considerable variability, with predominant types, including ST21, ST50 (ST21 CC), and ST3335 (ST206 CC), in human isolates, whereas ST50 and ST2116 (ST353 CC) prevailed in food sources. In contrast, C coli isolates were associated primarily with the ST828 CC. Cluster analysis based on core-genome multilocus sequence typing (cgMLST) revealed that 40.0% of the isolates formed 23 genetic clusters, suggesting potential outbreak scenarios. The isolates presented a high prevalence of ciprofloxacin resistance linked to mutations in GyrA (80.1%) and extensive tetracycline resistance attributed to tet genes (64.6%). Multidrug resistance was predominantly observed in C. coli (12.1%). Notably, the chromosomal erythromycin resistance gene erm(N) in food C. coli isolates was detected for the first time in Italy and for the first time worldwide in a veterinarian or food isolate. This One Health study, which was based on genomic surveillance, improved our understanding of antimicrobial resistance and the epidemiology of Campylobacter spp. This study highlights the emergence of a novel antimicrobial resistance marker in Italy, erm(N), and reveals the prospective occurrence of multiple nationwide outbreak scenarios that demand immediate public health attention.