Prevalence and Risk Factors of Drug Resistant Mycobacterium Tuberculosis in a Multisite Cohort Study

Drug -resistant tuberculosis (DRTB) has emerged as a major challenge in the control and prevention of TB. In the present study we first systematically reviewed the literature to characterize the diversity and frequency of gyrA and gyrB mutations in fluoroquinolone resistant Mycobacterium Tuberculosis (Mtb) and describe the global distribution of these mutations to help determine their potential utility and reliability as diagnostic markers for detecting phenotypic fluoroquinolone resistance in Mtb. Secondly, we describe the prevalence of and characteristics of DRTB in Mumbai, India, Chisinau, Moldova and Port Elizabeth, South Africa. The results from our systematic review revealed the gyrA mutations occurring most frequently in fluoroquinolone-resistant isolates, were D94G(21-32%) and A90V(13-20%) and that 83% and 80% of moxifloxacin and ofloxacin resistant strains respectively, were observed to have mutations in the gyrA codons interrogated by the existing MTBDRsl line probe assay. In China and Russia, 83% and 84% of fluoroquinolone resistant strains respectively, were observed to have gyrA mutations in the gene regions covered by the MTBDRsl assay. The results from our study found the overall prevalence of MDRTB was 79.7%, 51.1% and 15% in Mumbai, Chisinau and Port Elizabeth, respectively. Among the MDRTB patients, the prevalence of XDRTB in Mumbai, Chisinau and Port Elizabeth was 13.9%, 12.1% and 41.4%, respectively. A multiple logistic regression analysis showed that those less than 25 years of age (OR 1.8, 95%CI 1.0 to 3.1), study site (Mumbai (OR 33.1, 95% CI 18.8 to 58.3) and Chisinau (OR 13.0, 95%CI 6.8 to 24.6)), higher education (OR 2.4, 95%CI 1.4 to 4.0), ever been hospitalized (OR 1.9, 95%CI 1.2 to 2.9) and previously treated for TB (OR 1.7, 95% CI 1.1 to 2.8) were associated with developing M/ XDRTB. An interaction was also observed between study site and prior TB treatment. The burden of DRTB was high in all three sites highlighting the importance of continuous surveillance to identify DRTB, especially among patients who have been previously treated for TB. It is important to improve early diagnosis of MDRTB and to provide effective treatment to all MDRTB patients in order to prevent the development of additional drug resistanc