|VIRULENCE OF TUBERCLE BACILLI ISOLATED FROM PATIENTS
WITH TUBERCULOSIS IN BANGALORE, INDIA
|N Naganathan, B Mahadev, VK Challu, R Rajalakshmi,
Bharathi Jones DW Smith: Tubercle 1986, 67, 261-67.
Studies from Madras had shown that the strain of
M.tuberculosis isolated from south India were low virulent to guineapigs.
The relationship between virulence in guineapigs and pathogenesis
in humans could not be established earlier. A study was conducted
to investigate the relationship of virulence with the pathogenesis
by comparing the virulence of isolates from pulmonary tuberculosis
with that from patients with TB meningitis. The strains of bacilli
were obtained from three different sources: a) Sputum from rural
tuberculosis patients living near Bangalore city, b) sputum of TB
patients living in the city and c) from Cerebrospinal fluid (CSF)
of patients suffering from tuberculous meningitis and admitted in
different institutions in Bangalore city. The specimens were processed
by standard recommended procedures and cultured on Lowenstein Jensen
medium. The identification of an isolate as M. tuberculosis was
based on the niacin test. Albino Guinea pigs of both sexes (who
were bred and raised at this Institute) were used for the tests.
The virulence assay and the calculation of the root-index of the
virulence (RIV) were carried out according to the Mitchison method.
1) As per the RIV method, virulence has been classified
into low, moderate and high. The study showed that the percentages
of cultures having isolates of low, moderate and high virulence,
were the same as that of isolates obtained from patients in Madras,
reported by Mitchison et al., in 1960. 2) The distribution of the
RIV of virulence of isolates from patients living in the city of
Bangalore was significantly different (p < 0.05) from that of
isolates from patients living in rural Bangalore. 3) The number
of cultures classified as high virulent were significantly greater
in isolates from patients with tuberculous meningitis compared with
those from patients with pulmonary tuberculosis. However, 36%
of the isolates from the meningitis group were of low virulence.
|KEY WORDS: M.TUBERCULOSIS, VIRULENCE, RURAL
PATIENTS, URBAN PATIENTS.