Presence of Region of Difference 1 among Clinical Isolates of Mycobacterium tuberculosis from India

摘要

Region of difference 1 (RD1) was first described by Mahai-ras et al. (4) as a region that is present in all virulent laboratory and clinical strains of Mycobacterium bovis and Mycobacterium tuberculosis. This region comprises nine genes (Rv3871 to Rv3879c) and spans a 9.5-kb region. In M. bovis BCG, RD1 deletion completely removes seven genes (Rv3872 to Rv3878) and truncates two others (Rv3871 and Rv3879c) (3). Recently Rao et al.(5) reported the total absence of RD1 in clinical isolates from India.Since this region has genes that are important in immunogenicity (ESAT6 and CFP10 genes) and RD1 deletion mutants of M. tuberculosis have been found to be less virulent (3),it was important to study this region in other Indian isolates.In this study,we analyzed 120 M. tuberculosis isolates from different parts of Kerala and 23 other isolates,14 from west India and 9 from north India (mainly from Mumbai and Agra).All these isolates were characterized by biochemical analysis and IS6110 restriction fragment length polymorphism typing. The IS6110 copy number ranged from 0 to 15,with the majority (70) representing the "low-copy-number" group.The presence of the RD1 region was checked with three sets of primers.The locations of the primers on the H37Rv genome and the sizes of the expected amplicon and the reference are indicated in Fig.1#