Genetic Diversity In Clinical Mycobacterium Tuberculosis Isolates From Punjab

OBJECTIVE: To explore genetic diversity among the clinical Mycobacterium tuberculosis isolates prevalent in Punjab.DESIGN: Fifty-six random clinical isolates of M. tuberculosis were cultured from the sputum specimens of pulmonary tuberculosis patients. DNA was extracted from cultured biomass and analysed using the mycobacterial interspersed repetitive units (MIRU) typing method.RESULTS: MIRU typing of 51 isolates revealed 45 different patterns, with a combined Hunter-Gaston discriminatory index (HGDI) of 0.990. Five clinical isolates failed to amplify for one or more MIRUs and were excluded from the analysis. The remaining isolates were categorised in three groups based on the allelic heterogeneity of individual MIRUs. MIRU 10, 16,26 and 31 were highly discriminant, with an HGDI value > 0.6; MIRU 4, 23, 24, 39 and 40 were designated as moderately discriminant (HGDI value 0.6-0.3) and MIRU 2,20 and 2,7 were poorly discriminant (HGDI value < 03).CONCLUSION: MIRU typing and the HGDI values revealed that M. tuberculosis strains from Punjab are genetically quite heterogeneous.