Discrimination between Invasive and Contaminating Staphylococcus epidermidis strains according to the multiplex-PCR and study of phenotypic drug resistance

Background and Aim: With increase Staphylococcus epidermidis infections, discrimination between invasive and non-invasive S. epidermidis strains and determination of drug resistance, for diagnosis and treatment is important. Materials and Methods: From August 2014 to March 2015, 123 strains isolated from patients and medical instruments from Ali Asghar and Hazrat Rasoul hospitals were used to discriminate invasive and contaminating S. epidermidis strains by ica, atlE, agrA, sarA, and mecA genes by Multiplex PCR method. Also, according to the CLSI standards, resistance to cefoxitin, linzeolid, clindamycin, erythromycin and tetracycline were tested by disk diffusion method and vancomycin E-test method. Results: prevalence of ica and mecA genes were 85% and 75% in invasive strains and 20% and 51% in contaminating strains, respectively. The resistance level to cefoxitin, tetracycline, clindamycin and erythromycin antibiotics in invasive strains were: 75℅, 35℅, 37℅, 76℅ and in contaminating strains were; 51℅, 40℅, 30℅, 64℅, respectively. Resistance to vancomycin and linezolid was not observed in this study. Conclusions: This study shown that ica gene can be used as a suitable marker for discrimination between invasive and contaminating isolates. Also, vancomycin is a better choice for the treatment of resistant patients to methicillin. KeyWords: Invasive Staphylococcus epidermidis, Methicillin, Disk diffusion, Multiplex PC