• Campylobacter coli
• Campylobacter jejuni
• cgMLST
• Genetica di popolazione
• MLST

Campylobacter spp. are among the microorganisms most commonly associated with foodborne disease. The infection occours mainly by the handling or consumption of undercooked chicken meat or by the ingestion of contaminated raw milk. Studying the epidemiology of the disease and the emergence of drug-resistant Campylobacter are fundamental research topics to prioritize food safety interventions and to establish proper control strategies. This study characterized Campylobacter strains isolated from different animal reservoir and humans by using whole-genome sequencing to detail the genetic diversity of circulating strains and to examine the predominant clusters in Italy. We reconstructed a global phylogeny from Italian isolates and we attributed the source of infection using the attribution model revealing that most cases were linked to chicken as the main reservoir in Italy, followed to a lesser extent by the following sources: cattle; environment; wild bird; small ruminant, and pork. Then, we investigated the genomic constitution and antimicrobial resistance (AMR) of 238 Campylobacter from pigs and wild boars in Italy. The clustering using global MLST profiles showed specific Italian clusters and a clear separation between pig and wild boar profiles. Minimum inhibitory concentrations (MIC) of six antibiotics revealed higher resistance in pigs to ciprofloxacin, nalidixic acid, streptomycin and tetracycline, compared to wild boar. In contrast, most strains were susceptible to gentamicin. Worrying levels of multidrug resistance (MDR) were observed mostly in pig isolates. Finally, we stydied the antimicrobial resistance (AMR) genotypes of C. jejuni isolated from humans, poultry and birds from wild and urban Italian habitats to identify correlations between phenotypic and genotypic AMR in the isolates. We found out that in farmed chickens, the incidence of AMR was higher than other bird groups, confirming that the food-production birds are much more exposed to antimicrobials. The improper and overuse of antibiotics in the human population and in animal husbandry has resulted in an increase in antibiotic-resistant infections, particularly fluoroquinolone resistant ones. Assessing the genetic diversity among Campylobacter species is essential to our understanding of epidemiology and population structure. In the next future, integrated infectious disease surveillance systems that include molecular typing, epidemiology, ecology, and evolutionary processes, can improve understanding of the emergence and re-emergence of pathogens. Moreover, a better understanding of the AMR mechanisms in C. jejuni is necessary to develop new strategies for improving AMR programs and provide the most appropriate therapies to human and veterinary populations.