Combination of commercially available molecular assays and culture based methods in diagnosis of tuberculosis and drug resistant tuberculosis

Prevalence of Mycobacterium tuberculosis mutations associated with isoniazid and rifampicin resistance: A systematic review and meta-analysis

Tuberculosis (TB) is still one of the leading causes of worldwide death, especially following the emergence of strains resistant to isoniazid (INH) and rifampicin (RIF). This study aimed to systematically review published articles focusing on the prevalence of INH and/or RIF resistance-associated mutations of Mycobacterium tuberculosis isolates in recent years. Literature databases were searched using appropriate keywords. The data of the included studies were extracted and used for a random-effects model meta-analysis. Of the initial 1442 studies, 29 were finally eligible to be included in the review. The overall resistance to INH and RIF was about 17.2% and 7.3%, respectively. There was no difference between the frequency of INH and RIF resistance using different phenotypic or genotypic methods. The INH and/or RIF resistance was higher in Asia. The S315T mutation in KatG (23.7 %), C-15 T in InhA (10.7 %), and S531L in RpoB (13.5 %) were the most prevalent mutations. Altogether, the results showed that due to S531L in RpoB, S315T in KatG, and C-15 T in InhA mutations INH- and RIF-resistant M. tuberculosis isolates were widely distributed. Thus, it would be diagnostically and epidemiologically beneficial to track these gene mutations among resistant isolates.

Revisiting the methods for detecting Mycobacterium tuberculosis: what has the new millennium brought thus far?

Tuberculosis (TB) affects around 10 million people worldwide in 2019. Approximately 3.4 % of new TB cases are multidrug-resistant. The gold standard method for detecting Mycobacterium tuberculosis, which is the aetiological agent of TB, is still based on microbiological culture procedures, followed by species identification and drug sensitivity testing. Sputum is the most commonly obtained clinical specimen from patients with pulmonary TB. Although smear microscopy is a low-cost and widely used method, its sensitivity is 50-60 %. Thus, owing to the need to improve the performance of current microbiological tests to provide prompt treatment, different methods with varied sensitivity and specificity for TB diagnosis have been developed. Here we discuss the existing methods developed over the past 20 years, including their strengths and weaknesses. In-house and commercial methods have been shown to be promising to achieve rapid diagnosis. Combining methods for mycobacterial detection systems demonstrates a correlation of 100 %. Other assays are useful for the simultaneous detection of M. tuberculosis species and drug-related mutations. Novel approaches have also been employed to rapidly identify and quantify total mycobacteria RNA, including assessments of global gene expression measured in whole blood to identify the risk of TB. Spoligotyping, mass spectrometry and next-generation sequencing are also promising technologies; however, their cost needs to be reduced so that low- and middle-income countries can access them. Because of the large impact of M. tuberculosis infection on public health, the development of new methods in the context of well-designed and -controlled clinical trials might contribute to the improvement of TB infection control.

Evaluation of the QuantaMatrix Multiplexed Assay Platform for Molecular Diagnosis of Multidrug- and Extensively Drug-Resistant Tuberculosis Using Clinical Strains Isolated in Myanmar

Background

Although the incidence of tuberculosis (TB) is decreasing, cases of multidrug-resistant (MDR) TB and extensively drug-resistant (XDR) TB continue to increase. As conventional phenotype drug susceptibility testing (pDST) takes six to eight weeks, molecular assays are widely used to determine drug resistance. we developed QuantaMatrix Multiplexed Assay Platform (QMAP) MDR/XDR assay (QuantaMatrix Inc., Seoul, Korea) that can simultaneously detect mutations related to both first- and second-line drug resistance (rifampin, isoniazid, ethambutol, fluoroquinolones, second-line injectable drugs, and streptomycin).

Methods

We used 190 clinical Mycobacterium tuberculosis (MTB) strains isolated from Myanmar, compared QMAP and pDST results, and determined concordance rates. Additionally, we performed sequence analyses for discordant results.

Results

QMAP results were 87.9% (167/190) concordant with pDST results. In the 23 isolates with discordant results, the QMAP and DNA sequencing results completely matched.

Conclusions

The QMAP MDR/XDR assay can detect all known DNA mutations associated with drug resistance for both MDR- and XDR-MTB strains. It can be used for molecular diagnosis of MDR- and XDR-TB to rapidly initiate appropriate anti-TB drug therapy.