Journal Article

Antibiotic Resistance Profiles of Commensal and Pathogenic Bacteria Isolated from Wild Boar Carcasses in Campania Region, Southern Italy

Sollena, Lorena, Fioretti, Alessandro, Akwongo, Claire Julie, Murru, Nicoletta, Houf, Kurt, Peruzy, Maria Francesca, Borrelli, Luca

2026

Overview

Background/Objectives: Antimicrobial resistance (AMR) in wildlife is an emerging public health concern due to the risk of zoonotic transmission, especially through the food chain, yet data on free-ranging animals remain scarce. This study examined the presence and patterns of AMR among bacteria isolated from hunted wild boars in the Campania region of Italy. Methods: Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) was used to identify bacterial isolates from wild boar meat and carcass swabs to the species level, and the Kirby–Bauer disk diffusion test was applied to screen 205 isolates, spanning 20 bacterial genera, against a panel of clinically relevant antibiotics. Resistance metrics were analyzed at genus and antibiotic levels, and patterns were visualized using a hierarchically clustered heatmap. Results: Resistance was detected in 15 of the 20 genera, with full susceptibility observed in Acinetobacter, Arthrobacter, Glutamicibacter, Leclercia, and Rahnella. Overall, 67.3% (138/205) of the isolates showed resistance to at least one antibiotic, with 33.7% (69/205) classified as multidrug-resistant (MDR). Carbapenems retained the highest activity (≥95% susceptibility) among all genera tested, while amoxicillin/clavulanate (78.4%) and aztreonam (57.4%) exhibited the highest mean resistance. Among potential pathogens, Escherichia coli exhibited an extended-spectrum β-lactamase (ESBL)-like phenotype, with resistance to amoxicillin/clavulanate (67%), aztreonam (54%), and ceftazidime (47%) but preserved carbapenem susceptibility. Staphylococcus spp. showed pronounced resistance to linezolid (57%) and erythromycin (52%), whereas Pseudomonas isolates demonstrated elevated resistance to aztreonam and ceftazidime (57% each). Opportunistic pathogens such as Alcaligenes faecalis and Pantoea agglomerans showed peak resistance to ciprofloxacin and amoxicillin/clavulanate. Pathogens and opportunistic pathogens demonstrated higher mean resistance (>30%) than commensals (≤32%), but the difference in mean and median resistance levels was not statistically significant (Mann–Whitney’s U test, W = 4, p = 0.39). Conclusions: These findings highlight the widespread occurrence of AMR and MDR phenotypes, with clinically significant resistance patterns in wild-boar-associated bacteria, including non-pathogenic strains, highlighting their role in the amplification of AMR. Although the preservation of carbapenem susceptibility underscores their potential as last-line antibiotics, the high resistance to commonly used antibiotics raises concerns for zoonotic transmission. Surveillance of wildlife reservoirs therefore remains critical for integrated AMR control.

• Publisher: MDPI AG,Multidisciplinary Digital Publishing Institute (MDPI)
• Subject: Alcaligenes / Amoxicillin / Animals / Antibacterial agents / Antibiotic resistance / Antibiotics / Antimicrobial agents / Antimicrobial resistance / Arthrobacter / Aztreonam / Bacteria / Beta lactamases / Carbapenems / Carcasses / Ceftazidime / Ciprofloxacin / Commensals / Drug resistance / Drug resistance in microorganisms / E coli / epidemiology / Erythromycin / Escherichia coli / Food chains / Food contamination & poisoning / Genera / Genes / High resistance / Hogs / Ionization / Linezolid / Mass spectrometry / Mass spectroscopy / Meat / Multidrug resistance / Multidrug resistant organisms / One Health / Organisms / Oxytetracycline / Pathogens / Phenotypes / Public health / Statistical analysis / Surveillance / Susceptibility / Veterinary medicine / wild boar / Wildlife / Zoonoses / β Lactamase