Association of fluoroquinolone resistance with rare quinolone resistance-determining region (QRDR) mutations and protein-quinolone binding affinity (PQBA) in multidrug-resistant Escherichia coli isolated from patients with urinary tract infection.

BACKGROUND

Urinary tract infections (UTIs) caused by Escherichia coli pose significant public health risks, particularly in developing countries like Bangladesh. This study aimed to elucidate resistance patterns among UTI isolates and comprehensively investigate the mutational spectrum and its impact on drug-microbe interactions.

METHODS

We collected and identified E. coli isolates from hospitalized UTI patients at Dhaka Medical College Hospital and determined their resistance patterns using the disc diffusion method and broth microdilution. Quinolone resistance-determining regions (QRDRs) of the target genes (gyrA, gyrB, parC, and parE) associated with fluoroquinolone resistance were amplified by polymerase chain reaction (PCR) and analyzed through BTSeq™ sequencing for mutations, followed by molecular docking analysis using PyMOL and AutoDock for the protein-quinolone binding affinity (PQBA) study.

RESULTS

All isolates (100 %) displayed multidrug resistance, with chloramphenicol (16 % resistant) and colistin (28 % resistant) demonstrating superior efficacy compared to other antibiotics. The isolates resistant to colistin, as determined by disc diffusion testing, exhibited remarkably high minimum inhibitory concentrations (MICs), with one isolate registering an MIC exceeding 512 µg/mL. Alarming resistance rates were observed for five antibiotic classes, except for polymyxins (28 % resistant) and protein synthesis inhibitors (48 % resistant). Fifty-two percent (52 %) of the isolates exhibited resistance to all five tested quinolones. Sequence analysis revealed a novel L88Q mutation in ParC, affecting PQBA and binding conformation. Additionally, three ParC mutations (S80I, E84V, and E84G) and two ParE mutations (S458A and I529L) were identified, which had not been previously reported in Bangladesh. Among these, S80I appeared in all isolates. Double-mutations (S83L+D87N) in GyrA, L88Q and S80I in ParC, and I529L in ParE were identified as key drivers of fluoroquinolone resistance.

CONCLUSION

Our findings underscore the accumulation of significant mutations within QRDRs of UTI isolates, potentially compromising fluoroquinolone efficacy. The emergence of these novel mutations warrants further investigation to impede their dissemination and combat quinolone resistance.