Description of compensatory gyrA mutations restoring fluoroquinolone susceptibility in Mycobacterium tuberculosis

作者：Pantel Alix; Petrella Stephanie; Veziris Nicolas; Matrat Stephanie; Bouige Aurelie; Ferrand Helene; Sougakoff Wladimir; Mayer Claudine; Aubry Alexandra^*

来源：Journal of Antimicrobial Chemotherapy, 2016, 71(9): 2428-2431.

DOI：10.1093/jac/dkw169

Resistance to fluoroquinolones (FQs) in Mycobacterium tuberculosis (Mtb) is mainly due to mutations in DNA gyrase (GyrA(2)B(2)), with the most common substitutions located at positions 90 and 94 in GyrA. Two clinical MDR Mtb (MDR-TB) strains harbouring an A90E or D94N substitution in GyrA were found to be surprisingly susceptible to FQs (ofloxacin MIC a parts per thousand currency sign2 mg/L). We studied the impact of the additional GyrA substitutions found in these strains (T80A and T80AaEuroS+aEuroSA90G, respectively) on FQ susceptibility.
Mutants of interest were generated by site-specific mutagenesis of GyrA alleles. WT and mutant TB DNA gyrase subunits were overexpressed in Escherichia coli and purified, and the in vitro susceptibility to FQs of their DNA supercoiling reaction was studied.
IC(50)s of mutant gyrase complexes bearing GyrA D94N and A90E were 3- to 36-fold higher than WT IC(50)s, whereas IC(50)s of gyrase bearing T80AaEuroS+aEuroSA90GaEuroS+aEuroSD94N and T80AaEuroS+aEuroSA90E were close to the WT IC(50)s.
We demonstrated that substitutions T80A and A90G restore FQ susceptibility when associated with a substitution implicated in high-level FQ resistance. Line probe assay misclassification of MDR-TB strains as pre-XDR or XDR can be corrected by sequence analysis of gyrA.

• 出版日期2016-9