MRSA surveillance on livestock farms and meat.

Introduction: The objective of a collaborative OneHealth surveillance project was to investigate the prevalence of MRSA among livestock farms, persons working/living on these farms and on meat. Methods: Samples from Dutch broiler-, pig-, veal calf-, dairy cattle- and sheep farms, persons living/working on these farms and retail meat collected between 2018 – 2023 were cultured using (pre-) enrichment and selective plates. Next-generation sequencing of a subset of MRSA was performed to detect mecA/mecC, Panton-Valentine leucocidin (PVL) and to assign genogroups (GGs). Results: On 113/149 (75.8%) pig farms MRSA was present. The prevalence was lower among veal calf - (44/173; 25.4%), dairy- (11/181; 6.1%), sheep- (7/156; 4.5%), and broilers farms (0/195; 0%). Among 375 persons working/living on the farms, we identified 17 (4.5%) nasal MRSA carriers and all were farmers. All but two isolates from the farms belonged to GG0398 (= CC398). In total, 4529 Dutch retail meat samples were analyzed and 412 (9.1%) were MRSA-positive. Poultry meat was most often contaminated. Most meat isolates (97/148; 65.5%) belonged to GG0398. All but one isolate carried mecA, and all were PVL-negative. Conclusions: Despite the reduction of antimicrobial use by >70% in veterinary medicine since 2009, most pig farms are still MRSA positive. Farmers have a higher risk of being nasal MRSA carrier than persons in the general population. Meat is regularly contaminated with MRSA, but this is considered a limited risk for consumers. Almost all MRSA belonged to GG0398 confirming the continuous predominance of this type of MRSA in livestock and on meat.