Abstract
Antimicrobial-resistant bacteria causing intractable and even fatal infections are a major health concern. Resistant bacteria residing in the intestinal tract of healthy individuals present a silent threat because of frequent transmission via conjugation and transposition. Plasmids harboring quinolone resistance genes are increasingly detected in clinical isolates worldwide. Here, we investigated the molecular epidemiology of plasmid-mediated quinolone resistance (PMQR) in Gram-negative bacteria from healthy service trade workers. From 157 rectal swab samples, 125 ciprofloxacin-resistant strains, including 112 Escherichia coli, 10 Klebsiella pneumoniae, two Proteus mirabilis, and one Citrobacter braakii, were isolated. Multiplex PCR screening identified 39 strains harboring the PMQR genes (including 17 qnr,19 aac(6′)-Ib-cr, and 22 oqxA/oqxB). The genome and plasmid sequences of 39 and 31 strains, respectively, were obtained by short- and long-read sequencing. PMQR genes mainly resided in the IncFIB, IncFII, and IncR plasmids, and coexisted with 3–11 other resistance genes. The high PMQR gene carriage rate among Gram-negative bacteria isolated from healthy individuals suggests the high-frequency transmission of these genes via plasmids, along with other resistance genes. Thus, healthy individuals may spread antibiotic-resistant bacterial, highlighting the need for improved monitoring and control of the spread of antibiotic-resistant bacteria and genes in healthy individuals.
Highlights
125 non-duplicated ciprofloxacin (CIP)-resistant Gram-negative strains were isolated from 157 rectal swab samples; this corresponds to a carriage rate of
By analyzing the correspondence between drug resistance genes and drug resistance phenotypes (Table 3), we found that the drug sensitivity results for 10 strains of K
We found that the plasmid-mediated quinolone resistance (PMQR) gene carriage rate for K. pneumoniae was higher than that for E. coli, which was consistent with previous studies showing carriage rates for
Summary
Quinolones, a group of broad-spectrum antimicrobial agents, are widely used for treating infections caused by Gram-negative bacteria and are routinely used in animal breeding. In China, total antibiotic usage is estimated at approximately 162,000 tons/year [1], with human consumption accounting for approximately 48% and the remainder attributed to consumption by livestock and other domesticated animals [2]. Fluoroquinolone usage accounts for 17% of this total [3]. Three plasmid-mediated quinolone resistance (PMQR) mechanisms have been described: the first involves Qnr proteins, the second involves aac(60 )-Ib-cr genes, and the third involves oqxA, oqxB, and qepA plasmid-mediated efflux pumps [5,6].
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