Abstract:

Objective To study vancomycin-resistant Enterococcus（VRE） drug resistance genes and multilocus sequence typing（MLST）. Methods Totally,80 isolates of VAN-resistant Enterococcus faecium and 12 isolates of Enterococcus faecalis isolated from the clinical specimens in Sanya Central Hospital were collected and were identified by VITEK MS microbial identification system. The susceptibilities of VRE to 14 kinds of commonly used antibiotics were determined by VITEK 2 Compact automatic drug sensitivity test system. The minimum inhibitory concentrations（MIC）of vancomycin and tekoranin were determined by microdilution broth method. Virulence genotypes（esp,hyl,gelE,asal,cy1A,efaA and ace） and transposon structure of VRE isolates were screened by polymerase chain reaction（PCR）. MLST was used to analyze the multi-site sequence typing of VRE. Results A total of 80 isolates of Enterococcus faecium and 12 isolates of Enterococcus faecalis were identified by mass spectrometry. Both Enterococcus faecium and Enterococcus faecalis showed 100.0% drug resistance to vancomycin in in vitro drug susceptibility test,and the drug resistance rates to ampicillin were 97.5% and 50.0%,respectively,but the drug resistance rates to furantoin were low. All the isolates of VRE were resistant to vancomycin and tekoranin,and MIC were 192-256 and 32-256 μg/mL,respectively,representing VanA phenotype. All the VRE isolates were vanA genotype,and the proportion of esp virulence genotype was the highest（82.5%）,Enterococcus faecium was common in esp-hy1 gene combination,and Enterococcus faecalis was mainly in multi-gene combination. The Tn1546 transposon structure analysis could be classified into A-E types. MLST showed that 92 isolates of VRE could be classified into 7 ST types,including ST17（43.5%）,ST78（32.6%）,ST203（6.5%）,ST363（5.4%）,ST555（4.3%）,ST1392（4.3%） and ST1394（3.4%）,among which ST17 and ST78 were the most common types,belonging to CC17 clone complex. Conclusions The 92 VRE isolates are all multi-drug resistant isolates,vanA genotype and CC17 clone complex,and they are highly carrying drug-resistant genes and virulence genes.

Key words: Vancomycin-resistant Enterococcus, Isolate identification, Drug resistance, Genotype, Multilocus sequence typing