The correlation of drug resistance and virulence in Mycobacterium tuberculosis

The low success rates in the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant TB (XDR-TB), which account for 55% and 34% respectively, led the WHO to conclude that MDR/XDR-TB is a serious public health crisis. However, the virulence of MDR/XDR-Mycobacterium Tuberculosis(Mtb) has not been analyzed in details, which could provide a specific guidance for the control and prevention. In this review, we discuss different aspects of MDR/XDR-Mtb virulence and its relationship to fitness cost by probing the following questions: (1) what mediates the virulence of MDR/XDR-Mtb? (What is the relationship between fitness and virulence ofMtb? (2) Is it possible that drug-resistantMtb(DR Mtb) can show higher fitness? (3) What is the definite effect on fitness of each drug-resistant mutant? (4) What other important factors affecting fitness in the mutant strain? (5) How to study the virulence of a large number of DRMtb?And what prevention and control measures will be taken in the future, especially for the high virulent DRMtb? We therefore summarized the congruent relationship between drug resistance and fitness from the global response-related genes to antibiotic resistance-contributing mutation, provided methods to explore the virulence of DRMtb. This review may offer some critical information and concise guide to creating strategies for the prevention and control of drug-resistantMtb.