Methicillin-resistant Staphylococcus aureus GG0398 on livestock farms and meat in the Netherlands

Objectives: The objective of this collaborative surveillance project was to investigate the prevalence of methicillin-resistant Staphylococcus aureus (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 and 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 of 149 (75.8%) pig farms, MRSA was present. The prevalence was lower among veal calf (44/173; 25.4%), and dairy (11/181; 6.1%), sheep (7/156; 4.5%), and broiler 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 analysed 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 a 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 the MRSA belonged to GG0398 confirming the continuous predominance of this type of MRSA in livestock and on meat.