Study On Staphylococcal Cassette Chromosome Mec Genotype And Molecular Epidemiology Of Methicillin-resistant Staphylococcus Aureus

Objective To investigate the molecular epidemiology characteristics of SCCmec genotype of methicillin-resistant Staphylococcus aureus in hospital and community. To understand the relationship between Panton-Valentine leukocidin and the severity of the disease with MRSA infection and study Multilocus Sequence Typing of MRSA strains.Methods The phenotype of MRSA was screened by cefoxitin disk diffusion test. MRSA were identified of mecA gene by PCR. The genotypes of SCCmec were determined by multiplex PCR. Antibiotic resistance of MRSA strains were studied by ager dilution method.The PVL gene was detected by PCR. Then the PVL-positive strains were selected for MLST.Results Among 64 isolates of MRSA, SCCmec III,SCCmec II, SCCmecIVand nontypeable isolates accounted for 89.0% (57/64) ,1.6% (1/64) ,1.6% (1/64) ,7.8% (5/64) respectively. SCCmec type I and V strains were not discovered in our study. 63 HA-MRSA strains of 64 MRSA strains were multiple resistant to other antibiotics. The PVL gene of 63 HA-MRSA strains were negative.The rates of drug sensitive to chloramphenicol, cotrimoxazole were high. All the MRSA strains were sensitive to Vancomycin. Only one CA-MRSA strain was PVL-positive and the result of MLST was ST59. In addition toβ-lactam antibiotics were only resistant to lincosamide, macrolide and tetracycline.Conclusions The dominant epidemic strain of HA-MRSA was SCCmec type III. One CA-MRSA isolate was discovered in our region with the molecular characteristics of ST59-SCCmec type IV carrying the PVL virulence gene.SCCmec type III MRSA strains were multi-drug resistant. The drug resistance spectrum of CA-MRSA was narrower than that of HA-MRSA. It is of important significance monitoring of MRSA strains to guide the clinical use of antibiotics appropriately.