Methicillin-resistant Staphylococcus aureus in swine housed indoors in Galicia, Spain

Abstract

IntroductionLivestock are known reservoirs of methicillin-resistant Staphylococcus aureus (MRSA) and this constitutes an important public health issue. The prevalence of nasal MRSA carriers in swine housed indoors in Galicia, Spain, was studied. Methods197 samples from swine aged three, eight, 12, 16 and 24 weeks, and from adult pigs, were obtained from four farms. The cleaning procedures implemented to clean the barns and antimicrobial consumption were analyzed. Antimicrobial susceptibility and antimicrobial resistance genes were studied. PFGE, spa typing and MLST were used to classify the isolates. SCCmec, agr and pvl were analyzed. ResultsMRSA prevalence was 12.7%. Swine younger than 16 weeks had a higher colonization rate; 22.9% vs 3.5% (OR, 8.16; 95% CI, 2.47–29.79; p<0.01). The only farm found to be MRSA-free used disinfectants as part of its cleaning procedure. All MRSA were tetracycline-resistant (identifying the tetK and tetM genes), 80% were resistant to erythromycin and clindamycin and 16% were only clindamycin-resistant. The ermC and vgaA genes were identified in these two phenotypes. A single genotype (PFGE type A) and ST398 – spa t011 (84%) and t1451 (16%) were identified. SCCmec type V and agrI were identified in all isolates, and all were pvl-negative. ConclusionA correlation between swine age and MRSA colonization was observed. Appropriate cleaning procedures could have an impact on MRSA colonization in farming. Resistance to antibiotics used in human health was identified. Clinicians should be aware if their patients have come into contact with farm animals.