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Mycobacterium smegmatis moxifloxacin persister cells produce high levels of hydroxyl radical, generating genetic resisters selectable not only with moxifloxacin, but also with ethambutol and isoniazid

Swaminath, S and Paul, A and Pradhan, A and Sebastian, J and Nair, RR and Ajitkumar, P (2020) Mycobacterium smegmatis moxifloxacin persister cells produce high levels of hydroxyl radical, generating genetic resisters selectable not only with moxifloxacin, but also with ethambutol and isoniazid. In: Microbiology (United Kingdom), 166 (2). pp. 180-198.

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Official URL: https://doi.org/10.1099/mic.0.000874


Bacterial antibiotic persister cells tolerate lethal concentrations of antibiotics but emerge as the antibiotic-sensitive population upon antibiotics withdrawal. However, the possibility of antibiotic-resistant genetic mutants emerging from the antibiotic persister population in the continued exposure to microbicidal concentrations of antibiotics needed investigation. We explored this possibility using the fast-growing Mycobacterium smegmatis as a model organism for Mycobacterium tuberculosis biology, as it is known to incur antibiotic-resistant mutations identical to and at identical target positions as found in the clinical isolates of M. tuberculosis. Here we report that the moxifloxacin (MXF) persister population generate significantly elevated levels of hydroxyl radical. Hydroxyl radical being a sequence-non-specific mutagen, resulted in the emergence of moxifloxacin-resistant genetic mutants at 8-log10 higher frequency from the persister population. Luria-Delbruck experiment (in modified format) confirmed that MXF-resistant mutants emerged de novo from the persister population and were not pre-existent. The nature of the mutations in the quinolone resistance determining region indicated that they were generated due to oxidative stress. These mutations were identical to and at identical positions as found in the clinical isolates of MXF-resistant M. tuberculosis. Interestingly, from the MXF persister population, resisters to microbicidal concentrations of ethambutol and isoniazid could also be selected. These observations implied that the significantly high levels of hydroxyl radical might have generated genome-wide mutations, creating a pool of mutants in the MXF persister population, facilitating selection of resisters to other antibiotics also. These findings may be of clinical relevance to the emergence of drug-resistant strains during prolonged tuberculosis treatment regimen with high doses of multiple antibiotics. © 2020 The Authors.

Item Type: Journal Article
Publication: Microbiology (United Kingdom)
Publisher: Microbiology Society
Additional Information: The copyright for this article belongs to the Author(s).
Keywords: bacterial DNA; ethambutol; genomic DNA; hydrogen peroxide; hydroxyl radical; isoniazid; moxifloxacin; superoxide; bacterial protein; ethambutol; hydroxyl radical; isoniazid; moxifloxacin; tuberculostatic agent, antibiotic resistance; Article; bacterial cell; bacterial mutation; bacterial strain; bacterium culture; Candida cylindracea; controlled study; electron spin resonance; experimental design; flow cytometry; fluorescence; gene locus; lethal concentration; long term exposure; minimum bactericidal concentration; Mycobacterium smegmatis; Mycobacterium tuberculosis; nonhuman; oxidative stress; priority journal; bacterial genome; drug effect; drug tolerance; genetics; metabolism; microbial sensitivity test; mutation; Mycobacterium smegmatis; oxidation reduction reaction, Antitubercular Agents; Bacterial Proteins; Drug Resistance, Bacterial; Drug Tolerance; Ethambutol; Genome, Bacterial; Hydroxyl Radical; Isoniazid; Microbial Sensitivity Tests; Moxifloxacin; Mutation; Mycobacterium smegmatis; Mycobacterium tuberculosis; Oxidation-Reduction; Oxidative Stress
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 12 Jan 2023 11:22
Last Modified: 12 Jan 2023 11:22
URI: https://eprints.iisc.ac.in/id/eprint/79306

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