From Barns to Bushes: Exploring the ECOFF-Based Non-Wild-Type Status of Campylobacter spp. in Pets, Livestock, Synanthropic Birds and Wild Animals in Northwestern Italy.

INTRODUCTION: Antimicrobial resistance (AMR) poses a significant threat to both humans and animals. Zoonotic bacteria, such as Campylobacter, contribute to human infections and the spread of AMR, particularly through livestock, pets and wildlife. We investigated the prevalence, distribution and EUCAST ECOFF-based wild-type (WT) vs. non-wild-type (NWT) phenotypes in Campylobacter spp. isolated from different animal species in northwestern Italy, between 2014 and 2023. METHODS: Stool samples from owned dogs, livestock, wildlife and synanthropic birds were collected for Campylobacter isolation. Preputial lavages were additionally collected from bovines for C. fetus. Samples underwent isolation, identification and antimicrobial susceptibility testing using microdilution. Antimicrobial susceptibility was interpreted based on EUCAST epidemiological cut-off values (ECOFFs). RESULTS: Campylobacter jejuni was widely spread, accounting for 77.1% of all isolates (n = 384). The occurrence of C. coli and C. upsaliensis was mainly identified in swine and owned dogs, respectively. Overall, 38.0% (95% CI = 32.1-44.2) of the isolates demonstrated NWT susceptibility to at least one antimicrobial, and 23.8% exhibited NWT susceptibility to ≥ 3 antimicrobial classes. Non-wild-type patterns to fluoroquinolones and tetracyclines were the most common observed, especially among livestock isolates. The occurrence of NWT phenotypes varied by Campylobacter species and the animal source. C. coli showed a 2.85-fold increase in the risk of exhibiting an NWT phenotype compared to C. jejuni (95% CI = 2.24-3.62), and isolates from livestock displayed a higher probability of being NWT to fluoroquinolones (prevalence risk ratio = 5.49; 95% CI = 3.44-8.77) and tetracyclines (PR = 2.76; 95% CI = 1.58-4.83). CONCLUSIONS: This study provides evidence of NWT Campylobacter isolates based on EUCAST epidemiological cut-off values (ECOFFs) in both wild and domestic animal hosts in northwestern Italy. The high frequency of NWT isolates, particularly of fluoroquinolones and tetracyclines in livestock-associated isolates, aligns with concerns regarding antimicrobial use in the animal production sector. The detection of NWT isolates in wild animals suggests potential environmental dissemination and interspecies transmission.