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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.

Excessive use of antimicrobials and inadequate infection control practices has turned antimicrobial resistance (AMR) into a global, public health peril. We studied the expression of qnrA, qnrB, and qnrS plasmid in ciprofloxacin (CIP)-resistant strains of Escherichia coli in swine and humans from Romania, using the Polymerase Chain Reaction (PCR) technique. Antibiotic Susceptibility Testing (AST) for human subjects (H) on 147 samples and 53 swine (S) was ascertained as well as the isolation of bacterial DNA (E. coli) as follows: bacteriolysis, DNA-binding, rinsing, elution, amplification, and nucleic acids’ migration and U.V. visualization stages. From 24 samples of E. coli resistant to CIP collected from H subjects and 15 from S, for PCR analysis, 15 H and 12 S were used, with DNA purity of 1.8. The statistically analyzed results using the Crosstabs function (IBM SPSS Statistics-Ver. 2.1.), revealed the qnrS (417 bp) gene in 13 human subjects (52.0%), as well as in all swine samples studied. The qnrB (526 bp) gene was exposed in 9 of the human patients (36.0%) and in all swine isolates, and the qnrA (516 bp) gene was observed only in 3 of the isolates obtained from human subjects (12.0%) and was not discovered in pigs (p > 0.05). The presence of plasmids qnrA, qnrB, and qnrS in the human samples and of qnrB and qnrS in swine, facilitates the survival of pathogens despite the CIP action. The long-term use of CIP could cause a boost in the prevalence of qnr resistance genes, and resistance in the pigs destined for slaughter, a perturbing fact for public health and the human consumer.