First- and second-line drug resistance patterns among previously treated tuberculosis patients in India

Culture and drug susceptibility testing results of 2816 tuberculosis (TB) patients from across India who had failed repeated treatments from 2001 to 2004 were retrospectively analysed at the Tuberculosis Research Centre, Chennai. Of 1498 (53%) identified as having multidrug-resistant TB (MDR-TB), 671 (44.8%) were resistant to > or =1 second-line drugs (SLDs): 490 (32.7%) to ethionamide, 245 (16.4%) to ofloxacin and 169 (11.3%) to kanamycin; 69 (4.6%) were extensively drug-resistant TB (XDR-TB). Although from a highly select and non-representative patient group, such high SLD resistance levels, including XDR-TB, among MDR-TB patients is of concern. The prevention of MDR/XDR-TB through quality DOTS services, however, remains the priority. In addition, rapid scale-up of quality programmatic management under the RNTCP is needed, with more control and rational use of SLDs outside the programme.

Simultaneous infection with multiple strains of Mycobacterium tuberculosis identified by restriction fragment length polymorphism analysis

Simultaneous infection with multiple strains of Mycobacterium tuberculosis was confirmed in two isolates of a total of 543 culture-positive tuberculosis patients from the Model DOTS area of Thiruvallur, South India, using IS6110 and direct repeat restriction fragment length polymorphism (DR-RFLP). The two isolates showing different intensities of IS6110 band patterns were further analysed by repeating RFLP on their alternate cultures and individual colonies. The results showed respectively two and three distinct IS6110 RFLP patterns, indicating mixed infection. The possibility of cross contamination at laboratory or DNA level was ruled out. Additional DR-RFLP also confirmed infection with multiple strains. This study found evidence of co-infection with two or three different strains of M. tuberculosis, showing distinct RFLP patterns.