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Bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) has a significant morbidity and mortality. The aim of this study was to evaluate the efficiency of real-time polymerase chain reaction (Rt-PCR) targeting nuc and mec genes in the culture extracts of blood culture systems for the early diagnosis of MRSA. A total of 48 samples that gave positive growth signal in BACTEC 9000 MB (BD, USA) and stained as gram-positive cocci, were included in the study. The samples were collected between 2009 and 2010. VITEC 2 (bioMerieux, France) system was used for the identification and antibiotic susceptibility testing of the isolates. According to the culture results, 15 of the isolates were methicillin-resistant coagulase-negative staphylococci (MRCNS), four were MRSA, 14 were methicillin-susceptible coagulase- negative staphylococci (MSCNS) and 15 were methicillin-susceptible S.aureus (MSSA). However, Rt-PCR yielded 17 MRCNS, eight MRSA, 10 MSCNS and 13 MSSA results. Our findings indicated lack of concordance between blood culture and PCR technique. When the blood culture results were accepted as the gold standard for the determination of methicillin resistance, sensitivity, specificity, positive and negative predictive values of Rt-PCR were found as 73%, 62%, 56% and 78%, respectively. In conclusion, in contrast to the expectations, Rt-PCR was not considered as an appropriate method for the detection of MRSA in routine diagnosis.

The identification of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is becoming a hard task since colonization with MRSA is lasting for years and the number of the health care facilities other than hospitals is continuously increasing. In this study we aimed to investigate the genetic properties and health-care association of MRSA strains isolated from skin and soft tissue infections of outpatients admitted to Akdeniz University Hospital. Thirty strains were phenotypically identified as MRSA and after assessing the risk factors, 28 (93.3%) of them were classified as health-care associated (HCA) and 2 (6.7%) of them as community-acquired (CA). All of the isolates were positive for nuc and mecA genes by polymerase chain reaction. Antimicrobial resistance rates of HCA-MRSA and CA-MRSA isolates were found as follows, respectively; 89.3% and 0% for rifampin, 89.3% and 50% for ciprofloxacin, 89.3% and 0% for gentamicin, 50% and 50% for erythromycin, 28.6% and 0% for clindamycin, whereas all of the isolates were susceptible to vancomycin, linezolid and trimethoprim-sulfamethoxazole. SCCmec type III was detected in 24 (85.7%) of HCA-MRSA strains. SCCmec type IV was detected in 1 (3.6%) of HCA-MRSA and in 2 (100%) of CA-MRSA strains. Panton-Valentin leucocidin (PVL) gene positivity was detected in only CA-MRSA isolates (2/2; 100%). MRSA isolates were grouped into 17 different genotypes (from A to R) of which pulsotype A was predominant among HCA isolates and CA-MRSA isolates were found to be clonally related with each other. This is the first study which investigated the genetic properties of MRSA strains in Antalya (a province located at Mediterranean Region, Turkey). In this study HCA risk factors were investigated and CA-MRSA rate was only 6.7% among all MRSA strains isolated from outpatients. As a result of detailed investigation of HCA risk factors, it was possible to detect the exact rate of CA-MRSA among outpatients. Thus it is of clinical and epidemiological importance to know the origin of MRSA isolates since this will affect the empirical treatment choice. Genetic studies supplied by appropriate demographic data will help to clarify the evolution and epidemiology of MRSA in the community and in the hospital setting.

Panton-Valentin leucocidin (PVL) is a cytotoxin which causes tissue necrosis by degradating leucocytes and other cell types. PVL has recently become very up to date as it has been shown to be the major virulance factor of community acquired methicillin resistant Staphylococcus aureus strains. In this study, the presence of PVL was investigated in methicillin sensitive and resistant S. aureus (MSSA and MRSA, respectively) strains which were isolated from clinical samples between January 2005-May 2006 at Dokuz Eylul University Hospital, Izmir. Fifty five MRSA and 79 MSSA strains which were isolated from blood, wound and respiratory tract samples were randomly included to the study. The presence of PVL was evaluated by multiplex polymerase chain reaction (PCR) which detects pvl and S. aureus-specific nuc genes. As a result, PVL positivities were detected in two (5%) of 40 MSSA and four (10.3%) of 39 MSSA strains isolated in the years 2005 and 2006, respectively. None of the MRSA isolates had pvl gene. Although this cytotoxin was rarely detected among MSSA isolates, it was interesting to note that the prevalence of PVL was twice more in the year 2006 compared to 2005. It was also worth to notify that four of six (66.7%) PVL positive strains had been isolated from the patients of general surgery inpatient or outpatient clinics.