[Molecular characteristic of methicillin-resistant Staphylococcus aureus strains isolated in Moscow clinics]

OBJECTIVES; Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen of nosocomial infection. The goal of this work was to evaluate the clonality of hospital-acquired MRSA (HA-MRSA) circulating in Russian Federation and to compare different multiplex PCR techniques with SNP-based approach for MRSA typing.

Epidemiologically unrelated MRSA isolates (n = 62) from Moscow hospitals were selected for typing. Genomic DNA from clinical isolates was purified using the DNA express kit (Lytech Ltd, Russia). Staphylococcus chromosomal cassette mec (SCCmec) typing was performed by PCR using the previously described methods. Seven loci from five housekeeping genes (arcC162, arcC210, aroE132, gmk123, tpi241, tpi243 and yqiL333) were used for SNP-typing. Detection of particular nucleotides in selected loci was carried out in the thermocyclic primer extension reaction, followed by mass spectrometry of the products. Standard MLST procedure was performed as reference method.

The majority of the MRSA isolates (93.6%) belong to world-wide disseminated clonal complex (CC) 8. Three isolates (4.8%) belong to CC 1. All ST 239 isolates were found to carry SCCmec type III; ST 8 isolates, SCCmec type IV.

Among Russian MRSA CC 8 isolates carrying SCCmec IV type are predominant. SNP-typing is powerful toll for studies of molecular epidemiology of MRSA.