Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


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pISSN 2288-0585 eISSN 2288-6850

Molecular Detection of Fluoroquinolone Resistance in Multidrug-Resistant Mycobacterium tuberculosis Isolates

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2014 September, Volume 17, Issue 3, pages 80-85

Molecular Detection of Fluoroquinolone Resistance in Multidrug-Resistant Mycobacterium tuberculosis Isolates

Chang-Ki Kim1,3, Byung Soo Lee1, Myung Joon Choi1, Hee Jin Kim1, Kyungwon Lee2,3
1Korean Institute of Tuberculosis, 2Department of Laboratory Medicine, 3Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Korea


Background: Fluoroquinolones (FQs) are important drugs for treating multidrug-resistant tuberculosis (MDR-TB). However, due to widespread use of FQs, the resistance rates to FQs have been increasing among Mycobacterium tuberculosis. Rapid and reliable FQ drug susceptibility testing (DST) is crucial for successful treatment of MDR-TB. In this study, the feasibility of molecular detection of FQ resistance was evaluated.

Methods: A total of 95 MDR-TB isolates were collected from Jan through Oct 2009 at the Korean Institute of Tuberculosis. DST for ofloxacin (OFL), levofloxacin, and moxifloxacin was performed using the Lowenstein-Jensen media absolute concentration method. Minimum inhibitory concentrations (MIC) of these were determined using the broth microdilution method. DNA was extracted from cultured isolates using bead beating method. The quinolone resistance-determining region (QRDR) of gyrA and gyrB were amplified and those sequences were analyzed.

Results: Of 95 isolates, 79 were resistant to at least one of FQs. Of these, 71 (89.9%) harbored mutation in the QRDR of gyrA or gyrB. None of FQ susceptible strains possessed any mutation in gyrA or gyrB. Mutations in codon 94 of gyrA were most common; only two isolates had mutation in only the gyrB gene. OFL MICs for isolates with gyrA mutation ranged from 1 to 32 μg/mL, but FQ susceptible isolates showed MICs ranging from ≤0.06 to 0.5 μg/mL.

Conclusion: Mutation analysis of QRDR of gyrA and gyrB showed 89.9% sensitivity and 100% specificity for detecting FQ resistance in MDR-TB. Therefore, molecular DST can be useful for rapid detection of FQ resistance in MDR-TB. (Ann Clin Microbiol 2014; 17:80-85)


Fluoroquinolone, gyrA, gyrB, Multidrug- resistant tuberculosis