Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Veterinary Medicine, China Agricultural University, Beijing, People's Republic of China.
Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
J Antimicrob Chemother. 2020 Jun 1;75(6):1428-1431. doi: 10.1093/jac/dkaa037.
To report a novel tigecycline resistance gene, tet(X6), and its variants in four bacterial species isolated from chickens and pigs in China.
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.
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.
This study identified a novel type of tigecycline resistance gene, tet(X6), in Myroides, Acinetobacter and Proteus from chickens and swine. Tet(X6) conferred lower tetracycline/glycylcycline MICs than other Tet(X) variants, and ISCR2 may play a role in the transmission of tet(X6).
报道在中国鸡和猪源分离的 4 种细菌中发现的新型替加环素耐药基因 tet(X6)及其变体。
对替加环素耐药的嗜麦芽窄食单胞菌 18QD1AZ29W 进行 WGS 以鉴定疑似耐药基因。通过功能克隆、同源建模和分子对接，比较其与其他 Tet(X)变体的功能。对我们的 WGS 数据集中的 80 个分离株进行 tet(X6)的回顾性筛选，并分析 tet(X6)-阳性分离株的所有基因组环境。
2018 年从山东一猪场分离的耐替加环素嗜麦芽窄食单胞菌 18QD1AZ29W 携带 tet(X2)和一种新型 tet(X)基因 tet(X6)。tet(X6)仅将所有测试的四环素/甘氨酰环素对大肠杆菌的 MICs 增加了 2-4 倍，这可能是由于 Tet(X6)的四环素结合能力低于其他 Tet(X)变体。回顾性筛选显示，其他 7 个分离株（7/80，8.8%）来自山东和广东的鸡和猪，分别为 4 种变形杆菌属和 3 种不动杆菌属，它们对 tet(X6)的三种不同变体均呈阳性。基因组环境分析显示，来自嗜麦芽窄食单胞菌和普通变形杆菌的两个 tet(X6)阳性分离株分别含有 ISCR2，这可能在 tet(X6)的传播中发挥作用。
本研究在鸡和猪源的嗜麦芽窄食单胞菌、不动杆菌属和变形杆菌属中发现了一种新型替加环素耐药基因 tet(X6)。tet(X6)赋予比其他 Tet(X)变体更低的四环素/甘氨酰环素 MICs，并且 ISCR2 可能在 tet(X6)的传播中发挥作用。
