Description of compensatory gyrA mutations restoring fluoroquinolone susceptibility in Mycobacterium tuberculosis.
J Antimicrob Chemother
; 71(9): 2428-31, 2016 09.
Article
em En
| MEDLINE
| ID: mdl-27234461
ABSTRACT
OBJECTIVES:
Resistance to fluoroquinolones (FQs) in Mycobacterium tuberculosis (Mtb) is mainly due to mutations in DNA gyrase (GyrA2B2), 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 ≤2 mg/L). We studied the impact of the additional GyrA substitutions found in these strains (T80A and T80Aâ+âA90G, respectively) on FQ susceptibility.METHODS:
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.RESULTS:
IC50s of mutant gyrase complexes bearing GyrA D94N and A90E were 3- to 36-fold higher than WT IC50s, whereas IC50s of gyrase bearing T80Aâ+âA90Gâ+âD94N and T80Aâ+âA90E were close to the WT IC50s.CONCLUSIONS:
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.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Supressão Genética
/
Fluoroquinolonas
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DNA Girase
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Farmacorresistência Bacteriana
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Mycobacterium tuberculosis
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Antituberculosos
Limite:
Humans
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article