title: Extending the definition of the GyrB quinolone resistance-determining region in Mycobacterium tuberculosis DNA gyrase for assessing fluoroquinolone resistance in M. tuberculosis.
abstract: Fluoroquinolone (FQ) resistance is emerging in Mycobacterium tuberculosis. The main mechanism of FQ resistance is amino acid substitution within the quinolone resistance-determining region (QRDR) of the GyrA subunit of DNA gyrase, the sole FQ target in M. tuberculosis. However, substitutions in GyrB whose implication in FQ resistance is unknown are increasingly being reported. The present study clarified the role of four GyrB substitutions identified in M. tuberculosis clinical strains, two located in the QRDR (D500A and N538T) and two outside the QRDR (T539P and E540V), in FQ resistance. We measured FQ MICs and also DNA gyrase inhibition by FQs in order to unequivocally clarify the role of these mutations in FQ resistance. Wild-type GyrA, wild-type GyrB, and mutant GyrB subunits produced from engineered gyrB alleles by mutagenesis were overexpressed in Escherichia coli, purified to homogeneity, and used to reconstitute highly active gyrase complexes. MICs and DNA gyrase inhibition were determined for moxifloxacin, gatifloxacin, ofloxacin, levofloxacin, and enoxacin. All these substitutions are clearly implicated in FQ resistance, underlining the presence of a hot spot region housing most of the GyrB substitutions implicated in FQ resistance (residues NTE, 538 to 540). These findings help us to refine the definition of GyrB QRDR, which is extended to positions 500 to 540.
authors.affiliation: UPMC Université Paris, Laboratoire de Bactériologie-Hygiène, Paris, France.
authors.forename: Alix
authors.initials: A
authors.lastname: Pantel
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Petrella
authors.forename: Nicolas
authors.initials: N
authors.lastname: Veziris
authors.forename: Florence
authors.initials: F
authors.lastname: Brossier
authors.forename: Sylvaine
authors.initials: S
authors.lastname: Bastian
authors.forename: Vincent
authors.initials: V
authors.lastname: Jarlier
authors.forename: Claudine
authors.initials: C
authors.lastname: Mayer
authors.forename: Alexandra
authors.initials: A
authors.lastname: Aubry
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000096:biosynthesis / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004278:DNA, Superhelical / Q000187:drug effects / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D064704:Levofloxacin; D008297:Male; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D016296:Mutagenesis / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics*; D015242:Ofloxacin / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D014376:Tuberculosis / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D024841:Fluoroquinolones; D064704:Levofloxacin; D015242:Ofloxacin; D027081:DNA Gyrase