AUTHOR=Fan Xin-Yan , Jiang Yue , Wu Han , Liu Jie , Gu Qing-Yun , Wang Zhen-Yu , Sun Lin , Jiao Xinan , Li Qiuchun , Wang Jing 

TITLE=Distribution and spread of tigecycline resistance gene tet(X4) in Escherichia coli from different sources

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2024.1399732

DOI=10.3389/fcimb.2024.1399732

ISSN=2235-2988

ABSTRACT=<p>Tigecycline serves as a last-resort antimicrobial agent against severe infections caused by multidrug-resistant bacteria. Tet(X) and its numerous variants encoding flavin-dependent monooxygenase can confer resistance to tigecycline, with <italic>tet</italic>(X4) being the most prevalent variant. This study aims to investigate the prevalence and characterize tigecycline resistance gene <italic>tet</italic>(X) in <italic>E. coli</italic> isolates from various origins in Yangzhou, China, to provide insights into <italic>tet</italic>(X) dissemination in this region. In 2022, we tested the presence of <italic>tet</italic>(X) in 618 <italic>E. coli</italic> isolates collected from diverse sources, including patients, pig-related samples, chicken-related samples, and vegetables in Yangzhou, China. The antimicrobial susceptibility of <italic>tet</italic>(X)-positive <italic>E. coli</italic> isolates was conducted using the agar dilution method or the broth microdilution method. Whole genome sequencing was performed on <italic>tet</italic>(X)-positive strains using Illumina and Oxford Nanopore platforms. Four isolates from pig or pork samples carried <italic>tet</italic>(X4) and exhibited resistance to multiple antimicrobial agents, including tigecycline. They were classified as ST542, ST10, ST761, and ST48, respectively. The <italic>tet</italic>(X4) gene was located on IncFIA8-IncHI1/ST17 (n=2), IncFIA18-IncFIB(K)-IncX1 (n=1), and IncX1 (n=1) plasmids, respectively. These <italic>tet</italic>(X4)-carrying plasmids exhibited high similarity to other <italic>tet</italic>(X4)-bearing plasmids with the same incompatible types found in diverse sources in China. They shared related genetic environments of <italic>tet</italic>(X4) associated with IS<italic>CR2</italic>, as observed in the first identified <italic>tet</italic>(X4)-bearing plasmid p47EC. In conclusion, although a low prevalence (0.65%) of <italic>tet</italic>(X) in <italic>E. coli</italic> strains was observed in this study, the horizontal transfer of <italic>tet</italic>(X4) among <italic>E. coli</italic> isolates mediated by pandemic plasmids and the mobile element IS<italic>CR2</italic> raises great concerns. Thus, heightened surveillance and immediate action are imperative to curb this clinically significant resistance gene and preserve the efficacy of tigecycline.</p>