Efficiency of Microplate 7H11 Agar Proportion Method for Drug-Resistant Tuberculosis Surveillance in Upper Northern Thailand

Abstract

Efficiency laboratory tests for the diagnosis of drug-resistant TB is the main factor for success in TB treatment and control. Currently, Molecular biology techniques is an important role in the diagnosis. However, due to the high cost of the biomolecule technique for testing, some risk groups of drug-resistant tuberculosis still use the conventional method on solid media. This study developed a drug susceptibility testing using microplates containing the Middlebrook 7H11 agar for reducing turn-around time and the incubation space, aimed to compare the Canetti using Löwenstein–Jensen (LJ) medium and new method. 219 bacterial colonies on solid media were parallelly tested by two methods. Comparison showed that the results of the two assays perfect agreement for detection of TB, MDR-TB, rifampicin, streptomycin and streptomycin resistant isolates. The sensitivity, specificity, positive predictive values, negative predictive values and Cohen’s kappa coefficient were 100.0%, 98.7%, 95.6%, 100.0% and 0.9 respectively for detection of isoniazid resistant isolates. Time required for DST between new method and standard method is 28 and 42 days, average time is 24 and 36 days, respectively. The results showed high efficacy of this new method by comparing with standard method. In addition, this new method can reduce turn-around time and the incubation space. It is likely to be useful in high-endemic areas for surveillance as well as for the detection of drug-resistant tuberculosis in all risk groups.