Multi-drug resistant tuberculosis: current status and emerging tools for its management in India

Drug resistance in tuberculosis is a global problem and India is no exception. However, this rise is mainly among the previously treated cases, generally reported from the hospitals (majority of which are the tertiary health care centres). Primary resistance figures are still static and are mostly below 5% level. Detection of drug resistance in tuberculosis is conventionally performed by comparing the growth inhibition on the drug containing medium as compared to the drug free control (phenotypic methods). Since these methods are dependant on appearance of visible colonies of M. tuberculosis, these methods take longer time to provide susceptibility testing results and are labor-intensive. Therefore, alternate phenotypic methods based on the bacterial metabolism (CO2 production, Oxygen uptake, ATP bioluminescence etc) and thus the viability of organisms, have been tried and found promising in overcoming this hindrance of longer time requirement. These systems, besides having good sensitivity and impressive specificity as compared to the conventional methods, reduce the total turn around times for isolation as well as susceptibility testing of M. tuberculosis. Recent advances in our understanding of the molecular basis of drug resistance have led to the development of genotypic methods for detection of mutations/mechanisms associated with resistance. However, most of these phenotypic and genotypic advancements require expertise and expensive equipments/technologies, which limit their wider application. This article reviews current status of multi-drug resistance in tuberculosis (MDR-TB), the recent developments for its rapid and reliable detection and effective management with special reference to India.