Risk Factor Analysis for Occurrence of Linezolid-Resistant Bacteria in the Digestive and Respiratory Tract of Food-Producing Animals in Belgium: A Pilot Study.

Linezolid is a critically important antimicrobial used in human medicine. While linezolid is not licensed for food-producing animals, the veterinary use of other antimicrobials, such as phenicols (e.g., florfenicol), could cross/co-select for linezolid-resistant (LR) bacteria. Such LR strains pose a great concern for public health due to their potential transfer between animals and humans. This study explored possible associations between epidemiological risk factors, including phenicol use, and the occurrence of LR bacteria, such as enterococci and staphylococci, in poultry, pigs, and veal calves in Belgium. Florfenicol use significantly increased the likelihood of harboring LR bacteria in veal calves, sows, and fattening pigs, particularly for the digestive tract (odds ratio (OR): [3.19-5.29]) and the respiratory tract (OR: [6.11-9.09]). LR strains from feces from fattening pigs were significantly associated with production type (OR: [3.31-44.14]) and the presence of other animal species (OR: 0.41). The occurrence of LR strains in the respiratory tract from sows was also significantly associated with using antimicrobials other than florfenicol (OR: 10.07) and purchasing animals (OR: 7.28). Our study highlights the potential risks of using certain veterinary antimicrobials, such as florfenicol, in food-producing animals and emphasizes the need for responsible antimicrobial use to safeguard both animal and public health.