Detection of Extended Spectrum βeta Lactamase-producing (ESβL) bacteria in wild boar meat, carcasses and faeces: a food safety concern.

Antibiotic resistant bacteria, particularly ESβLs, are currently a major global public health challenge. Wild game, often overlooked in antimicrobial resistance research, represents a potentially significant player in the complex web of the antimicrobial resistance transmission pathway. This study aimed to screen wild boars hunted in Salerno province, southern Italy in 2023/2024 for carriage of ESβL-producing bacteria. To this end, meat, carcass swabs, and faeces from freshly killed wild boars presented to the Montesano sulla Marcellana slaughterhouse for processing and subsequent meat inspection, from various locations in Salerno Province were sampled. Following an enrichment step in Enterobacteriaceae enrichment broth, a plate culture was performed on the chromogenic Oxoid Brilliance ESβL agar. Presumptive ESβL isolates identified based on colony colours were re-seeded onto another Oxoid Brilliance ESβL agar plate and incubated to obtain single colonies. One colony from each plate was then sub-cultured on Tryptone soy agar and identified to species level using the matrix-assisted laser desorption ionisation time of flight mass spectrometry (MALDI-TOF MS). Overall, 20 different bacterial species were isolated from 85.7% of the wild boars sampled, with 16.3% originating from meat, 40.7% from carcass swabs and 43% from faeces. An average of 4 different species of EsβLs were isolated from each wild boar, with a higher presence in faeces, then in swabs and meat. E. coli was the most frequently isolated ESβLs from all sample types, representing 48.7% for faecal samples, 22.9% for swabs, and 14.29% for meat. Higher percentages were also observed for Bacillus cereus_thuringiensis_PG_IV (16.2%) and Klebsiella pneumoniae (8.1%) in faeces, Klebsiella pneumoniae (14.3%) and Proteus hauseri (11.43%) on swabs, and Klebsiella pneumoniae (14.29%) and Pseudomonas monteilii (14.29%) in meat. Additionally, emerging food borne bacteria including Escherichia fergusonii and Morganella morganii were also detected in meat. The detection of EsβLs in wild boar meat, carcass swabs, and faeces indicates the potential for antimicrobial resistance spread through wildlife, the environment and food chain, posing a public health risk from consumption of wild boars as well as interaction with wild game and its environment. Intensive efforts to control and prevent the spread and surge of antimicrobial resistance through wild boar meat chain are recommended.