Fecal Carriage of Escherichia coli Harboring the tet(X4)-IncX1 Plasmid from a Tertiary Class-A Hospital in Beijing, China

Abstract

The emergence of the mobile tigecycline-resistance gene, tet(X4), poses a significant threat to public health. To investigate the prevalence and genetic characteristics of the tet(X4)-positive Escherichia coli in humans, 1101 human stool samples were collected from a tertiary class-A hospital in Beijing, China, in 2019. Eight E. coli isolates that were positive for tet(X4) were identified from clinical departments of oncology (n = 3), hepatology (n = 2), nephrology (n = 1), urology (n = 1), and general surgery (n = 1). They exhibited resistance to multiple antibiotics, including tigecycline, but remained susceptible to meropenem and polymyxin B. A phylogenetic analysis revealed that the clonal spread of four tet(X4)-positive E. coli from different periods of time or departments existed in this hospital, and three isolates were phylogenetically close to the tet(X4)-positive E. coli from animals and the environment. All tet(X4)-positive E. coli isolates contained the IncX1-plasmid replicon. Three isolates successfully transferred their tigecycline resistance to the recipient strain, C600, demonstrating that the plasmid-mediated horizontal gene transfer constitutes another critical mechanism for transmitting tet(X4). Notably, all tet(X4)-bearing plasmids identified in this study had a high similarity to several plasmids recovered from animal-derived strains. Our findings revealed the importance of both the clonal spread and horizontal gene transfer in the spread of tet(X4) within human clinics and between different sources.

Characterization of an Escherichia coli Isolate Coharboring the Virulence Gene astA and Tigecycline Resistance Gene tet(X4) from a Dead Piglet

“…In recent years, plasmid-mediated tet (X4) gene transfer among animal-derived bacteria has caused wide public concern [ 4 ]. Notably, the IncX1, IncX3, IncHI1, and IncQ plasmids carrying the tet (X4) gene are most common and have been identified in Enterobacteriaceae [ 5 , 6 , 7 ]. Escherichia coli harboring tet (X4) have been isolated from multiple sources, including birds, retail meat, and the environment, and they have also been found in human clinical samples [ 8 , 9 , 10 , 11 , 12 ].…”