title: Induction of mycobacterial resistance to quinolone class antimicrobials.
abstract: An agar plate assay was developed for detecting the induction of drug-resistant mycobacterial mutants during exposure to inhibitors of DNA gyrase. When Mycobacterium smegmatis on drug-containing agar, resistant colonies arose over a period of 2 weeks. A recA deficiency reduced mutant recovery, consistent with involvement of the SOS response in mutant induction. The C-8-methoxy compounds gatifloxacin and moxifloxacin allowed the recovery of fewer resistant mutants than either ciprofloxacin or levofloxacin when present at the same multiple of the MIC; a quinolone-like 8-methoxy-quinazoline-2,4-dione was more effective at restricting the emergence of resistant mutants than its cognate fluoroquinolone. Thus, the structure of fluoroquinolone-like compounds affects mutant recovery. A spontaneous mutator mutant of M. smegmatis, obtained by growth in medium containing both isoniazid and rifampin, increased mutant induction during exposure to ciprofloxacin. Moreover, the mutator increased the size of spontaneous resistant mutant subpopulations, as detected by population analysis. Induction of ciprofloxacin resistance was also observed with Mycobacterium tuberculosis H37Rv. When measured with clinical isolates, no difference in mutant recovery was observed between multidrug-resistant (MDR) and pansusceptible isolates. This finding is consistent with at least some MDR isolates of M. tuberculosis lacking mutators detectable by the agar plate assay. Collectively, the data indicate that the use of fluoroquinolones against tuberculosis may induce resistance and that the choice of quinolone may be important for restricting the recovery of induced mutants.
authors.affiliation: Public Health Research Institute, New Jersey Medical School, UMDNJ, Newark, New Jersey, USA.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Malik
authors.forename: Kalyan
authors.initials: K
authors.lastname: Chavda
authors.forename: Xilin
authors.initials: X
authors.lastname: Zhao
authors.forename: Nirali
authors.initials: N
authors.lastname: Shah
authors.forename: Syed
authors.initials: S
authors.lastname: Hussain
authors.forename: Natalia
authors.initials: N
authors.lastname: Kurepina
authors.forename: Barry N
authors.initials: BN
authors.lastname: Kreiswirth
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kerns
authors.forename: Karl
authors.initials: K
authors.lastname: Drlica
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D000995:Antitubercular Agents / Q000494:pharmacology*; D001372:Aza Compounds / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D024841:Fluoroquinolones / Q000494:pharmacology; D000077734:Gatifloxacin; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D000077266:Moxifloxacin; D009169:Mycobacterium tuberculosis / Q000187:drug effects; D015242:Ofloxacin / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology*
chemical_list: D000890:Anti-Infective Agents; D000995:Antitubercular Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D011804:Quinolines; D002939:Ciprofloxacin; D064704:Levofloxacin; D015242:Ofloxacin; D000077734:Gatifloxacin; D000077266:Moxifloxacin