Characteristic of Drug Resistance in Staphylococcus aureus / 中华医院感染学杂志

ABSTRACT

OBJECTIVE To investigate the drug resistance and the prevalence of inducible clindamycin resistance in clinical isolates of Staphylococcus aureus and evaluate the clinical value of cefoxitin disk diffusion method and oxacillin disk diffusion for detection of meticillin-resistant S.aureus(MRSA).METHODS Bacteria identification and susceptibility test were performed by VITEK-2 system and K-B disk method.The PBP2a was detected by latex agglutination and MRSA was identified by cefoxitin disk diffusion method and oxacillin disk diffusion.The inducible resistance of erythromycin to clindamycin was checked by D-test according to the standards of CLSI(NCCLS).The statistical analysis was performed by WHONET 5.4 and SPSS 13.0 software.RESULTS Resistant rate to penicillin and ampicillin was 98.9% and 100.0%,respectively.Vancomycin-resistant(VRE) or intermediate strains were not found.Of the 93 S.aureus isolates,MRSA and meticillin-sensitive S.aureus(MSSA) were 58(62.4%) and 35(37.6%),respectively.The resistant rate of MRSA to 11 antibiotics was higher than MSSA.The sensitivity and specificity of cefoxitin disk diffusion method were 98.3% and 97.1%,respectively,those of oxacillin disk diffusion were 75.9% and 94.3%.Of the 9 isolates resitant to erythromycin but susceptible to clindamycin,5(55.6%) showed inducible resistance to clindamycin.CONCLUSIONS Resistance of S.aureus is quite serious.Cefoxitin disc diffusion method is a simple and reliable method for the detection of MRSA.The inducible resistance of erythromycin to clindamycin in S aureus should be checked by D-test in clinical microbiology laboratory routinely.