|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.
|RECOVERY OF TUBERCLE BACILLI FROM URINE OF PULMONARY
TUBERCULOSIS PATIENTS AND ITS COMPARISON WITH THE CORRESPONDING SPUTUM
|VK Challu, B Mahadev, R Rajalakshmi & K Chaudhuri:
Indian J TB 1989, 36, 107-11.
A study was done to compare (1) the filtration
method with conventional centrifugation method for the recovery
of tubercle bacilli from urine and (2) drug sensitivity profile,
virulence for guinea pigs and phage type of the urine isolates with
the corresponding isolates from the sputum of cases of bacillary
Urine specimens from 236 pulmonary tuberculosis
patients were cultured by routine centrifugation method as well
as filtration method. Filtration was done by passing urine through
a 0.45 um membrane filter and treating the membrane with 5% oxalic
acid for 15 minutes. LJ medium was used for culture in both the
methods. Centrifugation yielded 27 positives (11.6%) whereas
filtration gave 12 (12.6%) out of 95 specimens filtered. Contamination
was more with filtration method. Comparison of the biological
properties of M.tuberculosis isolated from urine and sputum of the
same patients revealed difference in drug sensitivity profile or
virulence for guineapigs for 13 of 25 (52%) of the pairs of isolates
tested. Moreover 4 of 11 pairs subjected to phage typing were found
to differ in both major and minor phage types. The significance
of these findings in the light of the pathogenesis of tuberculosis
is also discussed.
|KEY WORDS: FILTRATION, CENTRIFUGATION, SENSITIVITY,
VIRULENCE, SPECIFICITY, TUBERCLE BACILLI.
|BEHAVIOUR OF SOUTH INDIAN VARIANT OF M.TUBERCULOSIS
DURING EIGHT YEARS OF ANIMAL PASSAGE
|VK Challu, Sujatha Chandrasekaran, B Mahadev, Bharathi
Jones & R Rajalakshmi: Indian J TB 1993, 40, 191-94.
South Indian Variant strain of M.tuberculosis has
been found to be less virulent to guineapigs through various studies
from Madras and Bangalore. It was not known whether the low virulent
nature of the tubercle bacilli was a fixed character or a change
due to serial passages inside the body over a period of time. Hence,
a study was conducted to see the behaviour of low virulent tubercle
bacilli over a period of eight years during twenty passages in animals.
Ten low virulent cultures of M.tuberculosis isolated
from patients belonging to Bangalore area were injected intramuscularly
into guineapigs. The extent of lesions was assessed through Mitchison's
Virulence scoring method. Bacilli recovered from the spleen of these
guineapigs were passed into another set of animals and virulence
scored. Twenty serial passages were thus performed over a period
of eight years. The findings revealed that throughout the study
in all the passages, the south Indian Variant of M.tuberculosis
maintained its low virulent character.
|KEY WORDS: VIRULENCE, ANIMAL PASSAGE, M.TUBERCULOSIS.