Study On Staphylococcal Cassette Chromosome Mec Genotype And Antimicrobial Resistance Of Methicillin-resistant Staphylococcus Aureus In Xi’an

Objectives1. To collect the non-repeating methicillin-resistant staphylococcus aureusfrom inpatients and to genotype the staphylococcal cassette chromosomemec(SCCmec) of the isolates to define the main gene types in this area.2. To test the susceptibility of the isolates to vancomycin, teicoplanin,linezolid, levofloxacin and rifampicin and to define the minimum inhibitoryconcentration of each antibiotic.Methods1. Collecting the methicillin-resistant staphylococcus aureus of theinpatients in four Class AGrade3hospitals in Xi’an who were hospitalized fromJanuary to June in2011.2. Detecting mecA gene and the SCCmec genotypes by the polymerasechain reaction (PCR). 3. Detecting antimicrobial susceptibility to five antibiotics includingvancomycin, teicoplanin, linezolid, levofloxacin and rifampicin bymicrodilution broth method.Results1.147MRSA isolates were collected, among which,111were from malepatients and36were from the females, and62isolates(42.2％) were from Xijinghospital,36isolates(24.5％) were from Tangdu hospital,27isolates(18.4％)were from Xibei hospital and22isolates(15.0％) were from Zhongxin hospital.The median age of patients was59（range1～90）and50.3％of the patientswere over60years old. The shortest hospital stay was2days and the longesthospital stay was184days. The Intensive Care Unit, the department ofNeurosurgery and the department of Neurology were the three departments thatprovided the highest amount of MRSA isolates. Sputum was the most collectedspecimen (77.6％).2. All the147MRSA isolates were mecA positive. One of them wasSCCmecII, another one was SCCmecIVa, a third one was not defined by thismethod and144contained SCCmec type III.3. All the tested strains were susceptible to vancomycin, teicoplanin andlinezolid but showed a high resistant rate to levofloxacin and rifampicin (93.9％and87.1％). The MICof vancomycin was the lowest in all antibiotic.Conclusions1. The infection of MRSA usually occurs in the respiratory tract and thelungs. Intensive care unit and the department Neurology and the department ofNeurosurgery were departments the most MRSAinfection.2. SCCmec III may be the main gene types in Xi’an. 3. The study does not find the isolates which are resistant to vancomycin,teicoplanin and linezolid.4. Besides the vancomycin, teicoplanin and linezolid also has a very wellantibacterial activity to MRSA and we should think very carefully andcomprehensivly to decide which medicine is the best choice to treat the MRSAinfection.