Antimicrobial Resistance and Staphylococcal Cassette Chromosome mec Genotype of Meticillin-resistant Staphylococcus aureus from Lower Respiratory Tract / 中华医院感染学杂志

ABSTRACT

OBJECTIVE To investigate antimicrobial resistance and molecular epidemiology profiles of meticillin-resistant Staphylococcus aureus(MRSA)sampled from lower respiratory tract.METHODS Totally 107 MRSA strains were isolated from lower respiratory tract specimens at Shanghai Pulmonary Hospital between Dec 2005 and Dec 2006.PVL genes were detected by PCR.The genotypes of SCCmec were identified by multiplex PCR.The antimicrobial resistance of MRSA were tested by Kirby-Bauer agar dilution.We also performed the homology of 32 MRSA strains using pulsed-field gel electrophoresis(PFGE).RESULTS All of the 107 MRSA strains were negative in the PVL locus detection and the most frequent SCCmec types were type Ⅲ(81.3%),the others including type Ⅱ(15.9%),type Ⅳ(2.8%),type Ⅰ and type Ⅴ were not found in this group.Those 3 different types of SCCmec were all resistant to ?-lactam antibiotics,less resistant to rifampin,and susceptible to vancomycin,teicoplanin and daptomycin.The resistant rate of those 3 types were different to the non-?-lactam antimicrobial drugs such as trimethoprim/sulfamethoxazole,clindamycin,erythromycin,gentamicin,levofloxacin,and tetracycline,the resistant rate in the types Ⅱ and Ⅲ was significantly higher than the type Ⅳ.PFGE analyses assorted the 32 MRSA strains into 4 PFGE patternspulsotype A(25 strains),including subtypes A1(17strains),A2(1 strain)and A3(7 strains);pulsotype B(5 strains),pulsotype C(1 strain),and pulsotype D(1 strain).CONCLUSIONS This study does not found positive PVL locus in the MRSA strains in our hospital,the most frequent SCCmec types are type Ⅲ and some are type Ⅱ.PFGE presented that there are outbreaks of MRSA in ICU ward and TB ward No 5 at that time and the pandemic strains are subtypes A1 and A3,most of these MRSA strains are multiple resistant,which deserves attention from both the clinical staff and infection-control department of the hospital.