Comparative Analysis of Microscopic and Real-time Polymerase Chain Reaction-based Methods for the Detection of Multidrug Resistance in Mycobacterium tuberculosis

Abstract

In the current scenario, the rise of multidrug-resistant strains of Mycobacterium tuberculosis (MTB) poses a worldwide challenge. MTB is an acid-fast bacillus that shows varying degrees of mutation among different strains and is especially found to be resistant to two major drugs (antibiotics): rifampicin and isoniazid. Hence, the early diagnosis of multidrug resistance (MDR) is critical to initiate effective therapy against MTB and protect against the community spread of MDR strains. Till now, mainly, two diagnostic methods have been developed for determining pathogen and drug susceptibility/resistance of MTB, namely, phenotypic analysis using microscopic methods like acid-fast bacilli antibiotic culture along with Ziehl–Neelsen staining and molecular methods such as real-time qualitative/quantitative polymerase chain reaction (RT-qPCR). The key advantages of RT-qPCR over microscopic methods include the rapid detection and specificity of diagnosis. Microscopic methods on the other hand require long culturing times and sometimes lead to false-negative results that would result in improper treatment outcomes and/or the transmission of resistant MTB strain. In contrast, false-positive results can also occur in the molecular analysis due to genetic variations and the presence of a mixed population of susceptible/resistant MTB bacilli in the clinical samples, which may mask the susceptible genes. Consequently, the optimal approach for MDR detection will likely involve both microscopic and molecular methods to identify resistant strains that would facilitate the appropriate management of MDR-MTB by reducing its transmission and infection among the human population. Therefore, RT-qPCR should be accompanied by microscopic methods to improve the sensitivity of tuberculosis diagnosis.