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150
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.

151
RECOVERY OF TUBERCLE BACILLI FROM URINE OF PULMONARY TUBERCULOSIS PATIENTS AND ITS COMPARISON WITH THE CORRESPONDING SPUTUM ISOLATES
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 pulmonary tuberculosis.

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.

155
ROLE OF NON TUBERCULOUS MYCOBACTERIAL INFECTION IN IMMUNIZATION AGAINST TUBERCULOSIS
VK Challu, Sujatha Chandrasekaran, TR Sreenivas, MM Chauhan, Bharathi Jones, R Rajalakshmi, B Mahadev, VH Balasangameshwara & K Chaudhuri: Indian J TB, 1992, 39, 165-70.

One of the hypothesis put forth for the failure of BCG vaccine to show protection against bacillary pulmonary tuberculosis in Chingleput trial was the interference from non-tuberculous mycobacteria that were prevalent in the trial area. In order to test this, a study was conducted with the following objectives: to investigate (1) Protection given by BCG and M.avium intracellulare (MAI) which is the most prevalent species, against the challenge with high and low virulent strains of M.tuberculosis in sensitised guineapigs. (2) Whether M.avium Intracellulare (MAI) interferes with the protective effect of BCG against challenge with both high and low virulent strains of M.tuberculosis. Sensitization was done with MAI in guineapigs using both oral and intradermal routes. Groups of species were immunized with BCG/Placebo and later challenged with high/low virulent strains of M.tuberculosis. Colony counts of M.tuberculosis bacilli from spleens of the animals were done to measure the protective effect.
The findings were: (1) BCG showed protection against both high and low virulent challenges. (2) MAI in both oral and intradermal routes had no effect against low virulent challenge. (3) There was no significant interaction between BCG and MAI against low virulent challenge. (4) MAI when given orally, showed a significant protection against high virulent challenge. The same was not seen with intradermal route. (5) MAI orally, interfered with the protective effect of BCG against high virulent strains of M.tuberculosis.

KEY WORDS: BCG, PROTECTIVE EFFECT, NTM, M. AVIUM, INTRACELLULARE.

156
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.
 
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