RESUMO
Objective To determine the genotypes and their epidermiology of microlide, lincosamide and streptogramin B(MLS_B)resistant S.epidermidis isolates causing nosocomial infection.Method 126 isolates were collected from inpatients in three hospitals in Beijing from 2003-2004 for testing the antibiotic susceptibility to the macrolide erythromycin,the lincosamide clindamycin.The resistance phenotypes of erythromycin-resistant isolates were determined by the double-disc test with erythromycin and clindamycin.The presence of the relative genes(ermA,ermB,ermC and msrA)to MLS_B resistance was identified by PCR and the similarity of the isolates was analyzed by PFGE.Result The isolates were mostly resistant to macrolide and lincosamide.In the constitutive phenotype cMLS_B isolates,the methicillin resistant S.epidermidis(MRSE)proportion appeared high(78.5%),whereas high methicillin susceptible S.epidermidis(MSSE)proportion was found in the inducible MLS_B phenotype(iMLS_B) (69.2%).ermC was shown as the most frequent determinant to the resistance,not only in MRSE and MSSE (70.8% and 6.8%),but also in iMLS_B and cMLS_B(76.9% and 90.3%).No specific endemic strain was found by PFGE analysis.The same resistance phenotype pattern was not clustered together and distributed into type A～F at the similarity of 60%.Among the phenotypes(cMLS_B,iMLS_B and MS phenotype),no significant difference was shown in the PFGE genotype distribution.Conclusion Our results indicate that the MLS_B resistance in S.epidermidis causing nosocomial infection is prevalent in the hospital and MLS_B antibiotics should be used iudiciously,ermC was shown as the most frequent determinant to the resistance.