| Objective:Methicillin-resistant Staphylococcus aureus (MRSA) is an important multidrug-resistant pathogen that is found throughout the world. In this study, a diverse collection of261S. aureus isolates from human, animal, food and environmental sources were screened using genotypic and phenotypic methods to investigate the prevalence of methicillin-resistant S. aureus (MRSA) isolates based on the expression of the staphylococcal cassette chromosome nice (SCCmec),β-lactamase and other resistance genes, and antibiotic susceptibility testing.Methods:The antimicrobial sensitivity of S. aureus isolates were tested by K-B method; the incidence of drug resistance genes in Staphylococcus aureus were detected by PCR. The genotypes of SCCmec were determined by multiplex PCR. MLST was performed according to the sequences of7housekeeping genes.Results:(1) Of the261S. aureus strains that were characterized,213strains were methicillin-susceptible S. aureus (MSSA), and48strains were MRSA.(2) The rate of drug-resistance of48MRSA strains to Penicillin and Cefoxiti were all100%, to TrimethoPrim-Sulfamethoxazol and Tetracycline were85.42%and81.25%. The Vacomycin-resistance MRSA isolates have not be discovered. The rate of sensitive of213MSSA strains to Penicillin, Erythromycin and Tetracycline were71.36%,44.60%and27.70%. The resistance to all kinds of antibiotics of MRSA was significantly higher than MSSA (P<0.05).(3) Among all MRSA isolates have mecA gene, in which SCCmecⅢ, SCCmec V, SCCmecIV, SCCmec I and nontypeable isolates accounted for58.33%(28/48),22.92%(11/48),8.33%(4/48),2.08%(1/48) and8.33%(4/48). SCCmec type Ⅱ strains were not diseovered in our study. A lot of MRSA from people were SCCmecⅢ, accounted for77.78%(28/36), the MRSA from cattle were SCCmec V, the nontypeable isolates accounted for50%in pigs.(4) A total of195S. aureus isolates were MLST genotyped. There were42STs and12 new STs,10new allelees. The MRSA strains of human was SCCmecⅢ-ST239mainly, the MRSA of cattle was SCCmecⅢ-ST630mainly and the MRSA of pig was SCCmecⅤ-ST9mainly.Conclusion:(1) MRSA existed widely in the animals. The resistances to several antibiotics of MRSA were higher and had multiple drug resistance. The vacomycin-resistance MRSA isolates had not been discovered.(2) MSSA was more sensitive to all antibiotics than MRSA. SCCmec was closely associated with methicillin resistance in S. aureus isolates.(3) SCCmec genotyping and MLST classification could explain effectively the epidemiological characteristics of MRSA isolates. |
