A Study Of Antimicrobial Resistance And Molecular Epidemiology Of Methicillin-resistant Staphylococcus Aureus

OBJECTIVE: The objective is to study the isolating rate of MRSA (Methicillin-Resistant Staphylococcus Aureus) from 4 hospital in Hunan province, the isolating rate ofβ-lactamase and the antimicrobial susceptibility of MRSA; to compare some identification methods of MRSA; to study the homology of MRSA from the hospitalized patients in different time and 4 different hospitals, from the hospitalized patients and hospital environment. To analysis the characteristic of molecular epidemiology of MRSA, and provide reliable evidence for preventing the spread of MRSA.METHODS: 110 Staphylococcus aureus were isolated from the clinical samples of patients in 4 hospitals, 30 Staphylococcus aureus were isolated from the hospital environment and personnel in Xiangya Hospital. To detect the MRSA by using oxacillin disk diffusion test, cefoxitin disk diffusion test and MecA, FemA gene PCR assay.To detect theβ-lactamase by using nitrocephin sticks. The antimicrobial susceptibility of MRSA were tested by K-B disk diffusion test.To make sure if there were epidemic strains by analysising the plasmid profile. To study the homology of MRSA from the hospitalized patients and hospital environment in Xiangya Hospital, from the hospitalized patients in different time, from the hospitalized patients in 4 different hospitals by using Random Amplification of Polymorphic DNA (RAPD) analysis.RESULT: By using oxacillin disk diffusion test and cefoxitin disk diffusion test, 90 strains were found resistant to oxacillin, 1 strain intermediate, 49 strains sensitive; 89 strains were found resistant to cefoxitin, 51 strains sensitive. There were 89 strains detected MecA and FemA gene by PCR assay. Analysis of the false positive rate and false negative rate by X~2 test showed no significant difference between the results obtained by the two disk diffusion test. All the MRSA were sensitive to vancomycin and linezolid, but most of which were multiple resistant to other antibiotics. Among the 89 strains, 95.5% MRSA expressedβ-lactamase. 7 strains did not have detectable plasmid DNA. 82 strains were typed 17 distinct profile by using the plasmid profile. There were one or two epidemic plasmid of MRSA in the four hospital. A total of 5 distinct RAPD types (A, B, C, D and E) were categorized from the 89 strains, and 95.5% strains were the same types A. By using RAPD assay the strains there were homology of MRSA from the hospitalized patients and hospital environment in Xiangya Hospital, from the hospitalized patients in different time, from the hospitalized patients in 4 different hospitals.CONCLUSION: Oxacillin disk diffusion test and cefoxitin disk diffusion test are simple to perform, could rapidly, exactly detect the methicillin-resistant Staphylococcus aureus. And the cefoxitin disk diffusion test is more specific. The united detection MecA and FemA gene could exactly, effectively detect MRSA, which is more simple than the two gene amplify respectively. Among the 89 strains, 95.50% MRSA expressβ-lactamase, the rate is more higher than which other's report. All the MRSA were Multi-drug resistance (MDR), but sensitive to vancomycin and linezolid. The plasmid profile and RAPD assay are good for analysising the molecular epidemiology of MRSA. The MRSA strains have homology, and have been causing an outbreak in the 4 hospital.