Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of life-threatening human infections. The clinical impact of MRSA is mounting, not only due to the ever-increasing prevalence but also due to the occurrence of new, community-acquired MRSA strains. The aim of this prospective, multi-centre study was to determine the prevalence and genetic relatedness of clinically relevant MRSA isolates, in Turkey.

During a 1-year period, data from 20 successive patients with invasive S. aureus infections were collected from eight university hospitals, geographically distributed over the six main regions of Turkey. Among these S. aureus isolates, the genetic association of MRSA isolates was investigated by pulsed-field gel electrophoresis (PFGE) and spa typing. A selected number of isolates were also analyzed by multilocus sequence typing (MLST). Furthermore, Panton Valentine leucocidin (PVL) genes were examined.

In this study, the rate of methicillin resistance in S. aureus in patients with apparent infections (sepsis, meningitis, lung abscess or septic arthritis) ranged from 12 to 75% within the seven participating centres. Typing by pulsed-field gel electrophoresis and spa typing revealed the presence of 22 closely related genotypes. According to the PFGE and spa typing results, 53 out of 54 MRSA isolates were closely related. These isolates were of spa type t030 or a related spa type, contain an SCC mec type III element and belong to sequence type ST239. None of the isolates contained the PVL genes.

Despite the broad surface area of Turkey, a single predominant clone of ST239 circulates in hospitals in different regions and only few new types of MRSA were introduced over the past years. These results place Turkey in the epicenter of ST239 prevalence.