Epidemiological characteristics and genetic structure of linezolid-resistant Enterococcus faecalis Meijuan Chen,1 Hongying Pan,1 Yaling Lou,2 Zhe Wu,3 Jiajie Zhang,1 Yicheng Huang,1 Wei Yu,1,3,* Yunqing Qiu3,* 1Department of Infectious Diseases, Zhejiang Provincial People’s Hospital, People’s Hospital of Hangzhou Medical College, Hangzhou, China; 2Department of Infectious Diseases, Dongyang People’s Hospital, Jinhua, China; 3State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China *These authors contributed equally to this work Objectives: The aim of this study was to investigate the mechanism of linezolid resistance and evaluate the risk factors for linezolid-resistant Enterococcus faecalis (LZR-Efa) infections.Methods: A total of 730 E. faecalis isolates were collected, and whole-genome sequencing and bioinformatics analysis were performed. Meanwhile, risk factors related to linezolid resistance were analyzed by binary logistic regression.Results: Twenty-six LZR-Efa were isolated from various clinical samples, and 24 isolates were multidrug resistant. Four isolates were daptomycin nonsusceptible, while all LZR-Efa were susceptible to vancomycin. Thirteen different sequence types (STs) were identified, and the most prevalent type was ST16 (23.1%). The genes dfrE, lsaA, and emeA were identified in all isolates. A total of 23 E. faecalis were positive for optrA gene, and six amino acids mutations were identified among 18 LZR-Efa in OptrA. The 23S rRNA mutation was found in 16 LZR-Efa isolates. However, the presence of cfr was not identified. Furthermore, there were 41 virulence genes detected, and 10 genes (ace, bopD, cpsA, cpsB, ebpB, ebpC, efaA, fss1, fss2, and srtC) were found in all isolates. A total of nine isolates were positive for multiple virulent factors (ace, asa1, cylA, efaA, esp, and gelE). There was no difference in the number of virulence factors among different specimens (P