Abstract Plasmid-mediated quinolone resistance (PMQR) genes are widely present among Enterobacterales, leading to treatment failures, extended hospital stays, and increased mortality percentages. qnrS is one of important PMQR, which usually found in multi-resistance plasmids. However, limited information does exist about structure of qnrS 1-harboring plasmid in China. The aim of the present study was to investigate the sequence of a novel conjugative qnrS 1-harboring IncFIB plasmid (pFZ11). The plasmid was obtained from an E. coli sequence type 1312 strain previously identified in Fuzhou, China. pFZ11 was 79,147-bp in length and carried only one quinolone resistance gene, qnrS 1. In addition, it contained two β -lactamase genes ( bla TEM-1 and bla CTX-M-15), two streptomycin resistance genes ( strA and strB ), one trimethoprim resistance gene cassette ( dfrA 14), and a tetracycline resistance determinant ( tetA ). pFZ11 was transferred successfully into E. coli J53 Ar at a conjugation frequency of 3.5 × 10 –5 ± 1.9 × 10 –5 . pFZ11 could be maintained at 100% for 15 days without antibiotic stress. then pFZ11 gradually lost, but still remained above 94% until 30 days. The plasmid pFZ11 was highly similar to plasmid pPGRT46 from Nigeria. IS 2- qnrS 1- ISkra 4 module was found in pFZ11, which probably facilitates the mobilization of such quinolone resistance gene. Our study unveils one qnrS 1-haboring IncFIB conjugative plasmid from E. coli clinical isolate in China, shedding light on its transferability, stability, and genetic structure.
Zhao et al. (2026) studied this question.