# Phenotypic Antimicrobial Resistance of Some Bacterial Strains Isolated from Red Foxes (Vulpes vulpes) in Western Romania

## TL;DR

This study examines antimicrobial resistance in bacteria from red foxes in Romania to assess their role in tracking antibiotic resistance in the environment.

## Contribution

The study demonstrates that red foxes can serve as effective sentinels for monitoring antimicrobial resistance in wildlife and human-impacted areas.

## Key findings

- Multidrug-resistant Gram-negative bacteria like Escherichia coli and Salmonella were found in red foxes.
- Methicillin-resistant staphylococci were detected in both peri-urban and peri-rural areas.
- Antimicrobial susceptibility testing methods showed high agreement in results.

## Abstract

Background/Objectives: Recent investigations point to red foxes (Vulpes vulpes) as a very potent sentinel species for monitoring the dissemination of antimicrobial bacteria in wildlife habitats. Methods: This study investigated antimicrobial resistance in red foxes from 16 hunting grounds (peri-urban and peri-rural) in western Romania, between 2022 and 2024, in order to evaluate the species as “One Health” sentinels at the wildlife–human–animal interface. During this period, 137 bacterial strains previously identified from 216 samples were phenotypically tested using both the Kirby–Bauer disk diffusion method and the Vitek 2 Compact system. Results: Among the Gram-negative isolates, particularly Escherichia coli and Salmonella enterica, notable antimicrobial resistance and multidrug-resistant (MDR) phenotypes were observed, including resistance to third-generation cephalosporins (ceftazidime) and reduced susceptibility to carbapenems. Resistance patterns observed in Proteus spp. largely reflected intrinsic resistance traits. Methicillin-resistant and MDR staphylococci (Staphylococcus aureus, S. pseudintermedius and S. sciuri) were detected in both peri-urban and peri-rural hunting grounds, with higher frequencies observed in peri-rural areas. Although MDR prevalence was slightly higher in peri-urban compared to peri-rural sites, no statistically significant association was identified between area of isolation and antimicrobial resistance or MDR status. Antimicrobial susceptibility results obtained by disk diffusion and the Vitek 2 Compact system showed a high level of concordance for antibiotics tested in common. Conclusions: Overall, these findings support the use of red foxes as effective One Health sentinels for monitoring environmental antimicrobial resistance occurrence across wildlife, domestic animals, and human-impacted habitats.