Abstract
Background and Objectives: Staphylococcus epidermidis is one of the prevalent bacteria causing septicemia in neonates and children. Methicillin resistance in S. epidermidis isolates like S.aureus isolates has been shown and is of major clinical importance. This study was carried out to evaluate antibiotic resistance of S. epidermidis isolates and to detect methicillin resistance by oxacillin disc diffusion test and PCR.
Materials and Methods: Blood cultures of 2943 in-patients of Children Hospital of Tabriz with fever and signs of septicemia were studied, which 100 S. epidermidis isolates were recovered. Oxacillin disc(1µg) diffusion method and PCR were carried out to detect the methicillin resistance. Conventional disc agar diffusion test was also applied to evaluate the antibiotic sensitivity of our isolates against 9 routine use antibiotics according to CLSI (Clinical and Laboratory Standards Institute).
Results: Result of PCR showed mecA gene in 89 isolates out of 100 S. epidermidis, while 11 isolates lacked the mecA gene. Oxacillin disc method detected 85 resistant isolates, while 5 isolates with mecA gene were recorded as sensitive and one isolate lacking this gene was diagnosed as oxacillin resistant.
Conclusion: Oxacillin disc diffusion method showed sensitivity of 94.4% and specificity of 90.9% compared to PCR. Among routine use antibiotics the highest resistance was against penicillin and the least was against vancomycin. Results of this study indicated that oxacillin disc diffusion method had a low sensitivity and specificity in detection of methicillin resistance. Therefore accurate detection of methicillin resistance in S. epidermidis needs both phenotyping and genotyping methods.