Subinhibitory concentrations of nalidixic acid alter bacterial physiology and induce anthropogenic resistance in a commensal strain of Escherichia coli in vitro,Letters in Applied Microbiology

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Subinhibitory concentrations of nalidixic acid alter bacterial physiology and induce anthropogenic resistance in a commensal strain of Escherichia coli in vitro
Letters in Applied Microbiology ( IF 2.0 ) Pub Date : 2021-08-10 , DOI: 10.1111/lam.13550
J Chadha ₁ , L Khullar ₁

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The human gut houses a complex group of bacterial genera, including both opportunistic pathogens and commensal micro-organisms. These are regularly exposed to antibiotics, and their subinhibitory concentrations play a pivotal role in shaping the microbial responses. This study was aimed to investigate the effects exerted by sub-MICs of nalidixic acid (NA) on the growth rate, bacterial motility, biofilm formation and expression of outer membrane proteins (OMPs) in a commensal strain of E. coli. The NA-sensitive strain was sequentially passaged under sub-MICs of NA. E-test was used to determine the MIC values of NA. Results indicated significant changes in the growth profile of commensal E. coli upon exposure to NA at sub-MICs. Differential expression of OMPs was observed in cells treated with sub-MICs of NA. Bacterial motility was reduced under 1/2 MIC of NA. Interestingly, successive passaging under 1/2 MIC of NA led to the emergence of resistant E. coli with an increased MIC value of 64 µg ml⁻¹ in just 24 days. The NA-resistant variant was confirmed by comparing its 16S rRNA sequence to that of the sensitive commensal strain. Mutations in the Quinolone Resistance-Determining Regions (QRDRs) of chromosomal gyrA, and Topoisomerase IV-encoding parC genes were detected in NA-resistant E. coli. Our results demonstrate how antibiotics play an important role as signalling molecules or elicitors in driving the pathogenicity of commensal bacteria in vitro.

中文翻译：

萘啶酸的亚抑制浓度改变细菌生理学并诱导体外大肠杆菌共生菌株的人为抗性

人类肠道拥有一组复杂的细菌属，包括条件致病菌和共生微生物。它们经常接触抗生素，它们的亚抑制浓度在塑造微生物反应方面起着关键作用。本研究旨在研究萘啶酸 (NA) 的亚 MIC 对大肠杆菌共生菌株的生长速率、细菌运动性、生物膜形成和外膜蛋白 (OMP)表达的影响。NA 敏感菌株在 NA 的亚 MIC 下依次传代。E-test用于确定NA的MIC值。结果表明共生大肠杆菌的生长曲线发生了显着变化在亚 MIC 暴露于 NA 时。在用 NA 的亚 MIC 处理的细胞中观察到 OMP 的差异表达。在 NA 的 1/2 MIC 下，细菌运动性降低。有趣的是，在 NA 的 1/2 MIC 下连续传代导致耐药性大肠杆菌的出现，仅在 24 天内，MIC 值就增加了 64 µg ml ^-1。通过将其 16S rRNA 序列与敏感共生菌株的序列进行比较，确认了 NA 抗性变体。在耐NA 的大肠杆菌中检测到染色体gyrA的喹诺酮耐药性决定区 (QRDR)和编码拓扑异构酶 IV 的parC基因的突变. 我们的研究结果证明了抗生素如何作为信号分子或诱导物在体外驱动共生细菌的致病性方面发挥重要作用。

更新日期：2021-08-10

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