Reduced turn-around time for Mycobacterium tuberculosis drug susceptibility testing with a proportional agar microplate assay.
Multidrug-resistant tuberculosis is a major issue worldwide; however, accessibility to drug susceptibility testing (DST) is still limited in developing countries, owing to high costs and complexity. We developed a proportion method on 12-well microplates for DST. The assay reduced the time to results to <12 days and <10 days when bacterial growth was checked with the naked eye or a microscope, respectively. Comparison with the Canetti-Grosset method showed that the results of the two assays almost overlapped (kappa index 0.98 (95% CI 0.91-1.00) for isoniazid, rifampicin, streptomycin; and kappa index 0.92 (95% CI 0.85-0.99) for ethambutol). The sequencing of genes involved in drug resistance showed similar level of phenotype-genotype agreement between techniques. Finally, measurement of the MICs of rifampicin and ethambutol suggests that the currently used critical ethambutol concentration should be revised, and that the current molecular drug susceptibility tests for rifampicin need to be re-evaluated, as in vitro rifampicin-sensitive isolates could harbour drug resistance-associated mutation(s).
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam. Electronic address: vananhtdt@gmail.com.
V A T
VA
Nguyen
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam; MIVEGEC (IRD 224-CNRS 5290-Université de Montpellier), Centre IRD, Montpellier, France; Department of Biotechnology Pharmacology, University of Science and Technology of Hanoi, Vietnam.
H Q
HQ
Nguyen
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam.
T T
TT
Vu
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam.
N A T
NA
Nguyen
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam.
C M
CM
Duong
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam.
T H T
TH
Tran
Department of Microbiology, National Lung Hospital, Hanoi, Vietnam.
H V
HV
Nguyen
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam.
D A
DA
Dang
Department of Bacteriology, National Institute of Hygiene Epidemiology, Hanoi, Vietnam; MIVEGEC (IRD 224-CNRS 5290-Université de Montpellier), Centre IRD, Montpellier, France.
A-L
AL
Bañuls
D000362:Agar; D000995:Antitubercular Agents / Q000494:pharmacology*; D004198:Disease Susceptibility; D024901:Drug Resistance, Multiple, Bacterial; D004977:Ethambutol / Q000494:pharmacology; D005798:Genes, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics; D012293:Rifampin / Q000494:pharmacology; D018088:Tuberculosis, Multidrug-Resistant / Q000382:microbiology*
D000995:Antitubercular Agents; D004977:Ethambutol; D000362:Agar; D012293:Rifampin
Drug resistance; M. tuberculosis; MIC; drug susceptibility testing; proportional microplate assay; sequencing