Abstract:

Objective To study the drug resistance mechanism of 4 clinical isolates of linezolid non-sensitive Enterococcus faecalis. Methods Phenotype identification and in vitro antimicrobial susceptibility test of the 4 clinical isolates of linezolid non-sensitive Enterococcus faecalis were performed by Vitek 2 Compact microbial analysis system,and the minimum inhibitory concentration （MIC） of linezolid was rechecked by E-test strips. Chloramphenicol-florfenicol resistance （cfr） gene,23S rRNA V region and 4 copies of 23S rRNA were amplified and sequenced to find mutations. Results No cfr gene was found in the 4 clinical isolates of linezolid non-sensitive Enterococcus faecalis,and sequencing 23S rRNA V region did not find G2576U mutation. After further amplification and sequencing of 4 copies of 23S rRNA,only G2576U mutation was found in 1 isolate,and all 4 isolates contained U2826C mutation. G2389A,U2363C and A2881G mutations were also determined. Since U2826C was located at the edge of variable region of 23S rRNA,the sequcening results showed that linezolid non sensitive Enterococcus faecalis harbored U2826C mutation. Conclusions For the 4 clinical isolates of linezolid non-sensitive Enterococcus faecalis 23S rRNA,random mutation might be the main mechanism of drug resistance to linezolid.

Key words: Linezolid, Enterococcus faecalis, 23S rRNA, Drug resistance mutation