Plasmid copy number and qnr gene expression in selection of fluoroquinolone-resistant Escherichia coli

Abstract

Fluoroquinolone resistance in Enterobacteriales is developed by chromosomal and plasmid-mediated mechanisms. Plasmids play an important role in dissemination of resistant genes and they carry genes that protect bacteria in different stress-induced situations. In this study, we studied Escherichia coli strains, each carried one plasmidmediated quinolone resistance determinant namely, qnrA1, qnrB1, qnrC1, and qnrD1. We exposed 0.5 McFarland density of each strain to 0.5 mg/L ciprofloxacin from the period of 30, 60, 90, and 120 min over 24 h. All treated strains were further exposed to a constantly increasing 1, 2, 4, and 8 mg/L ciprofloxacin solution through 24, 48, and 120 h. In given timepoints, RNA was extracted from all treated strains. Expression of qnrA1, qnrB1, qnrC1, and qnrD1 was investigated by quantitative PCR. Mutations in gyrA and parC genes were analyzed by PCR and nucleic acid sequencing. In this study, during 0.5 mg/L ciprofloxacin exposition, the following expression levels were detected: 1.2 for qnrA1, 1.47 for qnrD1, 12.44 for qnrC1, and 80.63 for qnrB1. In case of long-term study, we selected a resistant strain in qnrB1-positive E. coli, and its expression increased from 105.91 to 212.31. On the contrary, plasmid copy number increased in time from 1 to 4.13. No mutations in gyrA or in parC chromosomal genes of treated strains were detected. Our results show that qnrB1-positive E. coli strain was able to develop fluoroquinolone resistance by upregulated qnrB1 expression that was linked to a minor increase in plasmid copy number but no mutations occurred in gyrA or parC.

Interplay between Phenotypic Resistance to Relevant Antibiotics in Gram-Negative Urinary Pathogens: A Data-Driven Analysis of 10 Years’ Worth of Antibiogram Data

“…It has been extensively described-both in Hungary and in other countries-that acquiring plasmid-borne fluoroquinolone resistance is a critical step towards the development of MDR in both Enterobacterales positive or negative for ESBL-production (as also demonstrated by our data analysis) [70]. Subsequently, these isolates will present with chromosomal or plasmid-mediated aminoglycosideresistance and resistance to other ancillary antibiotics (such as nitrofurantoin, fosfomycin, trimethoprim-sulfamethoxazole, and next-generation tetracycline-derviatives) [71]. In the end, the process ends with infections that may only be treated by carbapenems, novel β-lactam/β-lactamase-inhibitors, and colistin [72].…”

Delafloxacin, Finafloxacin, and Zabofloxacin: Novel Fluoroquinolones in the Antibiotic Pipeline

“…Additionally, in gram-negative pathogens, plasmid-mediated quinolone resistance (PMQR) determinants enhance development of fluoroquinolone resistance. PMQRs are represented by Qnr determinants, QepA and OqxAB efflux pumps, and aminoglycoside-acetyltransferase Ib-c variants [ 21 , 22 , 23 ].…”