| ObjectivesTo investigate the drug susceptibility of linezolid-resistant Enterococcus faecalis(LREfs)in our hospital,analyze the epidemiological characteristics,detect the resistance mechanism of the strains,and explore the risk factors for infection.MethodsThe LREfs from the First Affiliated Hospital of Zhejiang University from 2012 to 2015 were collected and the minimum inhibitory concentration(MIC)of strains against 16 drugs were determined using agar dilution method.High-throughput sequencing technology was used to perform whole-genome resequencing.The sequencing results were used for multi-sequence sequencing(MLST),and BioNumerics software was used to generate the minimum spanning tree(MST)analysis of strain phylogenetic relationships.The BLTRAN 2.3.0 software was used to detect the optrA gene,the cfr gene,and the mutation of 23 S rRNA V region.A retrospective case-control study of risk factors for the infection of LREfs was performed.ResultsA total of 26 linezolid-resistant enterococci were collected.,and after identification,they were all Enterococcus faecalis.The source of the specimens was mainly from urine,and the departments mainly focused on urology.Drug susceptibility results showed that 26 strains of LREfs were resistant to linezolid at low levels,with MIC values of 8 to 16 mg/l,all of which were sensitive to vancomycin,and 24 strains were multidrug resistant strains.The MLST classification results showed that 26 LREfs had 13 sequence types(ST):ST16 6 strains,ST585 5 strains,3 strains of ST476 and ST480 respectively,1 strain of ST479,ST21,ST619,ST116,ST81,and ST674 respectively.Three new types(ST856,ST857,ST858).The construction of MST showed that the LREfs in our hospital were scattered.The detection of drug resistance mutation and drug resistance gene showed that 23 strains were positive for optrA gene and 16 strains were detected 23SrRNA V-region mutations.cfr gene was not detected.Risk factor analysis showed that previous carbapenem antibiotics may be an independent risk factor for the infection of LREfs.ConclusionsLREfs in our hospital were mainly prevalent in the Department of surgery in sporadic.The phenomenon of multidrug resistance was quite serious,and all strains show a low level of drug resistance to linezolid.The optrA gene and the mutation in 23SrRNA V-region were the main mechanisms of drug resistance.The study of risk factors show that patients infected with LREfs in our hospital lacking the exposure of linezolid.Since some kinds of STs were found to be more popular in animal derived enterococcus,there was reason to speculate that the drug resistance gene in LREfs may come from animals via environmental contact. |
