Molecular typing of methicillin resistant Staphylococcus aureus isolates using Staphylococcal Cassette Chromosome mec (SCCmec) analysis

Objective: Staphylococcus aureus, with its virulence mechanisms and capacity to develop resistance against antimicrobial agents, is an organism that can cause serious, life-threatening infections. Methicillin-resistant Staphylococcus aureus (MRSA) strains are the leading cause of hospital-acquired infections in many countries. Since MRSA clones are easily spread throughout the world, it has become even more important to investigate the genotypic and evolutionary characteristics of these clones, along with the genetic and evolutionary relations between the strains isolated from different geographical regions.The aim of the present study was to determine the Staphylococcal Casette Chromosome (SCC) mec) types of MRSA strains isolated from various clinical samples obtained from hospitals of Dokuz Eyül University, İstanbul Medical School, Marmara University and the pediatric hospital of Hacettepe University, to investigate the presence of Panton-Valentine Leukocidin (pvl) gene in these isolates and to determine the molecular epidemiological relations in each center and between different centers using macrorestriction analysis.Method: A total of 207 isolates including 100 isolates from Dokuz Eylül Üniversity, 21 isolates from İstanbul University Medical School, 34 isolates from Marmara University Medical School and 52 isolates from Hacettepe University Pediatric Hospital were included in the study. There were no duplicate isolates from the same patients. The identification of the isolates was made in the respective microbiology laboratories of each center. The methicillin resistance of all isolates was tested again in our center, according to the ?CLSI? (Clinical and Laboratory Standarts Institute) recommendations. SCCmec types and the presence of PVL were investigated using multiplex polymerase chain reaction (PCR). The clonal relation between the isolates and the epidemiological status of each center was determined using the PFGE method, following SmaI enzyme restriction.Results: Of the isolates included in the study, 1 (0.5%) harbored SCCmec type II, 7 (3.4%) had SCCmec type III, 179 had SCCmec type III, 12 (6.7%) carried SCCmec type IV and 6 (2.9%) carried SCCmec type IVE. pvl gene was identified in 5 (2.4%) isolates. All PVL-positive strains contained the type IV SCCmec element. However, pvl gene was not present in all SCCmec type IV/IVE isolates. Except for type IV, pvl gene was not detected in the SCCmec types. It was determined that the isolates had 13 different pulsotypes according to their PFGE patterns. Overall, 87.4% of the isolates belonged to a dominant clone (the A clone). However, it was also determined that none of the strains carrying type IV/IVE SCCmec elements belonged to this clone. Of the isolates harboring SCCmec type IV/IVE, 55% were in the K pulsotype.Conclusion: The important aspects of our study, in which the great majority of the MRSA isolates harbored the SCCmec type III variant, are the detection of SCCmec type IV/IVE isolates and the finding that only a small part of these isolates contianed the pvl gene. Additionally, the fact that the type IV/IVE SCCmec element, which is known as a community-acquired MRSA SCCmec type, was detected in the hospital-acquired MRSA strains reflects the change in the epidemiology of MRSA. On the other hand, the finding that the pvl gene, which is a virulence factor of SCCmec type IV MRSA isolates, was not present in some isolates, points out to the necessity of querying the certainty of the relation between of SCCmec type IV and PVL.