Identification of the novel tigecycline resistance gene tet(X6) and its variants in Myroides, Acinetobacter and Proteus of food animal origin

作者：Dejun Liu, Weishuai Zhai, Huangwei Song, Yulin Fu, Štefan Schwarz, Tao He, Li Bai, Yang Wang, Timothy R. Walsh, Jianzhong Shen · 发表于：Journal of Antimicrobial Chemotherapy · 年份：2020 · DOI：10.1093/jac/dkaa037 · 被引用次数：98 · 研究领域：Antibiotic Resistance in Bacteria、Pharmaceutical and Antibiotic Environmental Impacts、Infections and bacterial resistance

OBJECTIVES: To report a novel tigecycline resistance gene, tet(X6), and its variants in four bacterial species isolated from chickens and pigs in China. METHODS: WGS was conducted to identify the suspected resistance genes in the tigecycline-resistant Myroides phaeus 18QD1AZ29W. Functional cloning, homology modelling and molecular docking were performed to compare the function with other Tet(X) variants. Retrospective screening for tet(X6) was conducted for 80 isolates in our WGS data collection, and all genomic environments of tet(X6)-positive isolates were analysed. RESULTS: The tigecycline-resistant M. phaeus 18QD1AZ29W isolated from a pig farm in Shandong in 2018 was positive for tet(X2) and a novel tet(X) gene, designated tet(X6). Tet(X6) could increase the MICs of all tested tetracyclines/glycylcyclines for Escherichia coli only 2- to 4-fold, which was possibly due to a lower tetracycline binding capacity of Tet(X6) compared with that of other Tet(X) variants. Retrospective screening showed that seven other isolates (7/80, 8.8%), comprising four Proteus spp. and three Acinetobacter spp. from chickens and pigs in Shandong and Guangdong, were positive for three different variants of tet(X6). The analysis of the genomic environment revealed that two tet(X6)-positive isolates from M. phaeus and Proteus cibarius, respectively, contained ISCR2, which may play a role in tet(X6) transmission. CONCLUSIONS: This study identified a novel type of tigecycline resistance gene, tet(X6...