High prevalence of SCC mec-associated Phenol-soluble modulin gene in clinical isolates of methicillin-resistant Staphylococcus aureus

Abstract

Introduction. We aimed to determine the distribution of Phenol-soluble modulin-mec (psm-mec) gene and its relationship with biofilm formation in clinical methicillin-resistant S. aureus (MRSA). Methods. In a descriptive study, a total of 94 cefoxitin-resistant S. aureus isolates were collected from patients and tested for antibiotic susceptibility testing, multiplex polymerase chain reaction (MPCR) for detection of mecA and pvl genes, PCR for detection of psm-mec gene and SCCmec typing of psm-mec and pvl-positive isolates. Furthermore, isolates were tested by microtiter plate method for biofilm formation assay. Results. Multiplex PCR for detection of mecA and pvl genes was performed for all cefoxitin-resistant isolates. The mecA gene was found in 92 (97.9) isolates but none of the isolates carried the pvl gene. Sixty-five (69.1) isolates harbored psm-mec genes and 95.4 of these isolates belong to SCCmec type III. Statistical analysis showed a significant difference between the presence or absence of psm-mec gene and biofilm production (P<0.001). Conclusion. In this study, more than half of the MRSA strains harbored psm-mec gene and almost one-fifth of them produced strong biofilm. Since the strains with strong biofilm formation have more antibiotic resistance and cause the long-lasting infection, for the suitable treatment of hospitalized patients with this kind of MRSA strains, we should be paid more attention to these strains.