Role of gyrB Mutations in Pre-extensively and Extensively Drug-Resistant Tuberculosis in Thai Clinical Isolates.
DNA gyrase mutations are a major cause of quinolone resistance in Mycobacterium tuberculosis We therefore conducted the first comprehensive study to determine the diversity of gyrase mutations in pre-extensively drug-resistant (pre-XDR) (n = 71) and extensively drug-resistant (XDR) (n = 30) Thai clinical tuberculosis (TB) isolates. All pre-XDR-TB and XDR-TB isolates carried at least one mutation within the quinolone resistance-determining region of GyrA (G88A [1.1%], A90V [17.4%], S91P [1.1%], or D94A/G/H/N/V/Y [72.7%]) or GyrB (D533A [1.1%], N538D [1.1%], or E540D [2.2%]). MIC and DNA gyrase supercoiling inhibition assays were performed to determine the role of gyrase mutations in quinolone resistance. Compared to the MICs against M. tuberculosis H37Rv, the levels of resistance to all quinolones tested in the isolates that carried GyrA-D94G or GyrB-N538D (8- to 32-fold increase) were significantly higher than those in isolates bearing GyrA-D94A or GyrA-A90V (2- to 8-fold increase) (P < 0.01). Intriguingly, GyrB-E540D led to a dramatic resistance to later-generation quinolones, including moxifloxacin, gatifloxacin, and sparfloxacin (8- to 16-fold increases in MICs and 8.3- to 11.2-fold increases in 50% inhibitory concentrations [IC50s]). However, GyrB-E540D caused low-level resistance to early-generation quinolones, including ofloxacin, levofloxacin, and ciprofloxacin (2- to 4-fold increases in MICs and 1.5- to 2.0-fold increases in IC50s). In the present study, DC-159a was the most active antituberculosis agent and was little affected by the gyrase mutations described above. Our findings suggest that although they are rare, gyrB mutations have a notable role in quinolone resistance, which may provide clues to the molecular basis of estimating quinolone resistance levels for drug and dose selection.
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Areeya
A
Disratthakit
National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Ministry of Science and Technology, Pathum Thani, Thailand Drug-Resistant Tuberculosis Research Fund, Siriraj Foundation, Bangkok, Thailand.
Therdsak
T
Prammananan
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Chanwit
C
Tribuddharat
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Iyarit
I
Thaipisuttikul
Department of Pathophysiology and Host Defense, Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Tokyo, Japan.
Norio
N
Doi
Drug-Resistant Tuberculosis Research Fund, Siriraj Foundation, Bangkok, Thailand.
Manoon
M
Leechawengwongs
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand Drug-Resistant Tuberculosis Research Fund, Siriraj Foundation, Bangkok, Thailand angkana.cha@mahidol.ac.th.
Angkana
A
Chaiprasert
D000631:Aminopyridines / Q000494:pharmacology*; D000995:Antitubercular Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D054908:Extensively Drug-Resistant Tuberculosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology*; D000077734:Gatifloxacin; D015870:Gene Expression; D006801:Humans; D064704:Levofloxacin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D015242:Ofloxacin / Q000494:pharmacology; D013785:Thailand / Q000453:epidemiology; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology
C530475:7-(7-amino-7-methyl-5-azaspiro(2.4)heptan-5-yl)-6-fluoro-1-(2-fluoro-1-cyclopropyl)-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid; D000631:Aminopyridines; D000995:Antitubercular Agents; D024841:Fluoroquinolones; D002939:Ciprofloxacin; D064704:Levofloxacin; D015242:Ofloxacin; D027081:DNA Gyrase; D000077734:Gatifloxacin; C061363:sparfloxacin; D000077266:Moxifloxacin