Occurrence and characterization of livestock-associated methicillin-resistant Staphylococcus Aureus

Abstract

Methicillin resistant Staphylococcus aureus causes a wide range of severe and economically-important diseases in humans and animals. Different types of MRSA are associated with different hosts but the transmission occurs between them. The aim of this study was to investigate possible spread of MRSA among livestock in Lithuania and to determine their types and antimicrobial resistance. Cattle (n=120), horses (n=120) pigs (n=160) and poultry (pooled samples, n=120) were tested for MRSA prevalence. From a total of 520 samples tested, 4 isolates of methicillin resistant Staphylococcus aureus (0.8 %) were identified. All isolates were obtained from the finisher pigs delivered from the same farm complex. Multiplex PCR demonstrated presence of mecA, nuc and 16S genes in all tested cultures. All MRSA isolates were identified as ST398. Sequencing of spa genes and SCCmec typing revealed that all strains belonged to the spa type t011 and SCCmec V. PFGE revealed two different clones among the isolates. Susceptibility testing revealed resistance to tetracycline in all MRSA isolates attributed to tetK and tetM genes. All tested isolates were resistant to erythromycin owing to the presence of ermB gene as well as resistances to azithromycin, clindamycin and quinupristin/dalfopristin. One isolate was resistant to trimethoprim/sulfamethoxazole and carried the resistance gene dfrK while the other isolate was resistant to the combination of amoxicillin and clavulanic acid. All of the isolates were susceptible to fluoroquinolones, cefotaxime, chloramphenicol, fosfomycin, fusidic acid, gentamicin, linezolid, vancomycin, mupirocin and teicoplanin