Molecular characterization of Staphylococcus aureus strains isolated from surgical site infections of patients in southern Poland

INTRODUCTION: The aim of the study was a molecular characterization of Staphylococcus aureus strains isolated from surgical site infections (SSIs) from patients in southern Poland, undergoing different surgical procedures, together with evaluation of the prevalence of antimicrobial resistance and the presence of virulence factors. MATERIALS AND METHODS: In this laboratory-based, multicenter study, non-repetitive 162 samples from SSI were collected from hospitalized patients (12 hospitals, n=139) or outpatients (n=23) in southern Poland between January 1 and December 31, 2013. In all S. aureus isolates, we investigated antimicrobial susceptibility, the presence of selected virulence genes (lukE, pvl, tsst-l and eta), and also conducted spa typing. RESULTS: Patients with SSI had a median age of 61 years; 54.9% were male. Prevalence of MRSA (29 strains, 17.9%) SSI per surgery type was 8.7% in orthopaedic, 17.7% in general and 42.9% in vascular surgery. Over 20% of strains were resistant for erythromycin (27.2%), clindamycin (23.5%). No resistance was found for linezolid, glycopeptides or tigecycline. Gene of Leukocidin (lukE) was the most frequently found gene. Spa typing identified 10 spa types; the two dominant types were t003 (41.4%) and t138(17.2%). CONCLUSIONS: The results show that after vascular surgery, there was an unexpectedly high prevalence of MRSA in SSIs in southern Poland. Conversely, the prevalence of MRSA was unexpectedly low following orthopaedics procedures. The surprisingly observation was the low virulence of the S. aureus strains among older patients.