R2539 Abstract (publication only) Detection and characterisation of methicillin-resistant Staphylococcus aureus strains isolated from pigs in Lithuania - a cross-sectional study N. Couto*, M. Ruzauskas, A. Belas, M. Virgailis, I. Klimiene, R. Siugzdiniene, C. Pomba (Lisbon, PT; Kaunas, LT)

Objectives: To investigate methicillin-resistant Staphylococcus aureus (MRSA) occurrence among pigs in Lithuania and to characterize isolated strains. Methods: Between January 2011 and December 2011, 120 nasal swabs were taken from randomly selected breeding pigs from 6 different farms and additionally 40 nasal swabs were obtained from finishing pigs from two other farms at two slaughter houses just before slaughtering. MRSA was screened on Brilliance^TM MRSA 2 Agar (Oxoid) and chromID^TM MRSA medium (bioMérieux) and confirmed by PCR for the presence of the mecA gene. MRSA isolates were subjected to spa typing, SCCmec typing, ST398 PCR, and underwent PFGE analysis with Cfr9I. Isolates were also tested for the lukF/lukS genes encoding Panton–Valentine leukocidin (PVL). Antimicrobial susceptibility testing was performed using the broth microdilution method (MicroScan® PM21; Dade Behring Siemens) and interpreted according to CLSI guidelines. The presence of tetK, tetM, ermA, ermB, ermC, vgaA, vgaC and dfrK genes was studied by PCR. Results: Four nasal swabs out of 160 (2.5%) were MRSA-positive. The isolates were obtained from animals of the same farm at slaughterhouse. The strains were CC398, spa type t011 and SCCmec V. None of the MRSA isolates carried the PVL genes. Analysis obtained by PFGE revealed that two isolates had similar profiles, while the other two clustered differently. Susceptibility testing revealed resistance to tetracycline in all MRSA isolates, attributed to tetK and tetM genes. All tested isolates were resistant to erythromycin and clindamycin owing to the presence of ermB gene. One MRSA strain was resistant to trimethoprim/sulfamethoxazole and carried the dfrK resistance gene. All isolates were susceptible to fluoroquinolones, mupirocin, fosfomycin, fusidic acid, rifampicin, chloramphenicol, gentamicin, netilmicin, linezolid, nitrofurantoin, teicoplanin and vancomycin. Conclusions: This study is the first report on the prevalence and characteristics of livestock- associated MRSA isolated in pigs in Lithuania. Since the MRSA strains were isolated just before slaughtering, pigs can potentially be reservoirs of bacteria that may enter the food chain. Furthermore, MRSA ST398 shows low host specificity and can colonize various animal hosts as well as humans, which raises the question of potential interspecies and zoonotic transmission.