Virulence of tubercle bacilli isolated from patients with tuberculosis in Bangalore, India.

This is a study of the virulence of cultures of Mycobacterium tuberculosis isolated from pulmonary and extrapulmonary forms of tuberculosis in patients living in or near Bangalore, India. The findings are as follows: 1. The percentage of cultures recovered from cases of pulmonary tuberculosis in Bangalore classified as being of low, moderate, and high virulence, was the same as that reported by Mitchison et al., in 1960 for isolates obtained from patients in Madras, India. 2. The distribution of the root index of virulence (RIV) of isolates from patients living in the city of Bangalore was significantly different (p less than 0.05) from that of isolates from patients living in rural Bangalore. 3. Even though the number of cultures classified as high virulent was significantly greater in isolates from patients with tuberculosis meningitis compared with those from patients with pulmonary tuberculosis, the data show that 36% of the isolates from the meningitis group were classified as low virulent.