Comparison of Oxacillin Agar Screening and PCR Methods in Detection of Methicillin Resistance Staphylococcus epidermidis Strains Isolated from Blood Cultures of Children

In recent years methicillin resistant Staphylococcus epidermidis is among the prevalent bacteria causing septicemia in neonates and children. Therefore the rapid diagnosis and their antibiotic resistance surveillance are of great importance for treatment. The aim of this study was to evaluate oxacillin screening agar with three concentrations of oxacillin and to compare with PCR in detection of methicillin resistant Staphyliococcus epidermidis. A total of 100 Staphylococcus epidermidis strains were recovered from blood cultures of neonates and children. Resistance of isolates to methicillin were checked using oxacillin agar screening containing 0.6, 4, and 6 μg/ml of oxacillin. They were also tested for mecA gene by PCR. According to PCR results 89 of test isolates revealed to have mecA gene. Oxacillin agar screening test containing 0.6 μg/ml oxacillin could detect 85 and 89 resistant strains after 24h and 48h incubation,respectively. The same test containing 4μg/ml oxacillin could detect 78 and 89 resistant strains after 24h and 48h incubation, respectively and by using 6 μg/ml oxacillin 67 and 75 resistant strains detected after 24h and 48h incubation, respectively. Sensitivity of oxacillin agar screening test containing oxacillin concentrations of 0.6μg/ml and 4μg/ml after 48h incubation were the same as PCR test, whereas 6μg/ml oxacillin showed low sensitivity in detection of resistant isolates. Therefore, oxacillin agar screening test with 0.6 μg/ml and 4 μg/ml after 48h incubation, which is a cheap and handy for any level of routine laboratory could be used in accurate and effective detection of methicillin resistant S. epidermidis (MRSE).