MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, PR China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu Province, PR China; Institute of Comparative Medicine, Yangzhou University, Yangzhou, Jiangsu Province, PR China.
J Glob Antimicrob Resist. 2022 Jun;29:105-112. doi: 10.1016/j.jgar.2022.02.012. Epub 2022 Feb 26.
Tigecycline is one of the last-resort treatments against multidrug-resistant (MDR) Gram-negative bacteria. Recently, a novel efflux pump gene cluster tmexCD1-toprJ1 has been identified to reduce the antibacterial activity of tigecycline. However, the epidemiological feature and the horizontal transfer of this cluster have not been thoroughly studied in chicken-origin strains.
Here, we found that the tmexCD1-toprJ1 gene cluster was present in 32.7% (16/49) of tigecycline-resistant Klebsiella pneumoniae (K. pneumoniae) isolates in a chicken farm. All the strains showed MDR phenotype, and the efflux pump inhibitor 1-(1-naphthylmethyl)-piperazine (NMP) synergized the activity of tigecycline to the tmexCD1-toprJ1-carrying strains by 8- to 128-fold. The S1 nuclease-pulsed field gel electrophoresis (S1-PFGE), and Southern blotting revealed that all the tmexCD1-toprJ1 gene clusters were located on plasmids with various sizes and could be transferred among strains by conjugation and transformation. Furthermore, the tmexCD1-toprJ1-carrying plasmid could have a fitness cost in recipient strains. Sixteen isolates belonged to two different sequence types (ST3332 and ST37), and they were classified into two distinct lineages. Importantly, one plasmid was found to co-harbour tmexCD1-toprJ1 and mcr-8.5, which may pose a potential threat to public health.
This study demonstrates the clonal dissemination in tmexCD1-toprJ1-carrying K. pneumoniae strains in the chicken farm.
替加环素是治疗多药耐药（MDR）革兰氏阴性菌的最后手段之一。最近，一种新的外排泵基因簇 tmexCD1-toprJ1 被发现降低了替加环素的抗菌活性。然而，该基因簇在鸡源菌株中的流行特征和水平转移尚未得到彻底研究。
在这里，我们发现 32.7%（16/49）的鸡场耐替加环素肺炎克雷伯菌（K. pneumoniae）分离株中存在 tmexCD1-toprJ1 基因簇。所有菌株均表现出 MDR 表型，外排泵抑制剂 1-（1-萘基甲基）-哌嗪（NMP）使 tmexCD1-toprJ1 携带株对替加环素的活性协同增加了 8 至 128 倍。S1 核酸酶脉冲场凝胶电泳（S1-PFGE）和 Southern 印迹显示，所有的 tmexCD1-toprJ1 基因簇均位于大小各异的质粒上，并可通过接合和转化在菌株间转移。此外，tmexCD1-toprJ1 携带质粒可能会给受体菌株带来适应度成本。16 个分离株属于两种不同的序列型（ST3332 和 ST37），它们分为两个不同的谱系。重要的是，发现一个质粒同时携带 tmexCD1-toprJ1 和 mcr-8.5，这可能对公共卫生构成潜在威胁。
本研究表明，鸡场中携带 tmexCD1-toprJ1 的肺炎克雷伯菌菌株存在克隆传播。
