Objective. The aim of this work was to characterize MSSA strains in Poland as a potential source for newly emerging MRSA strains and to compare these with the simultaneously circulating MRSA clones.
Methods. The study was performed on 183 isolates sent to the National Medicines Institute (NMI) during 6 month survey fom September 2006 to February 2007. The clonal structure of the isolates was studied by MLVF, PFGE, MLST, spa-typing and SCCmec typing. Detection of the PVL coding genes was performed by PCR.
Results. MLST revealed 11 different clonal complexes (CCs) and 3 different singletons in this study. Ninety-nine MRSA and MSSA isolates shared the background of the five major MRSA lineages: CC5, CC8, CC22, CC30 and CC45. MSSA isolates belonged also to CC1, CC7, CC12, CC15, CC25 and CC51. None of CCs with only MRSA isolates was detected. For the first time in Poland the MSSA isolates of ST22 were detected as well as single isolate of ST22-IV (Barnim clone). PVL positive isolates were detected among MSSA ST121 (singleton) and ST15 (CC15) and MRSA belonged to ST8-IV (CC8). None of the MSSA shared the background with the most common ST80 CA-MRSA in Europe
Conclusions. We conclude:
1. PVL positive MSSA strains of ST121 and ST15 can be a potential source of PVL positive CA-MRSA strains.
2. A pool of circulating MSSA strains is important parameter with regard of the epidemiology of hospital and community-acquired MRSA clones in Poland.