|INVITRO STUDY ON SENSITIVITY OF TUBERCLE BACILLI
TO THIOACETAZONE (TB1)
|K Padmanabha Rao, SS Nair, N Naganathan & G Ramanatha
Rao: Indian J TB 1966, 13, 147-57.
This report is based on the study of 735 cultures
of tubercle bacilli identified as human type. Sputum specimens were
collected from patients attending the Lady Willingdon Tuberculosis
Demonstration and Training Centre (LWTDTC), Bangalore, and from
the mass Case-finding studies in semi-urban areas. Drug sensitivity
tests for streptomycin, isoniazid, PAS and thioacetazone with different
drug concentrations, different size of inoculum and for various
length of incubation were carried out.
No difference was observed in the duration of growth
between sensitive and resitant cultures in their first appearance
on primary diagnostic cultures or sub-cultures on drug free slopes
when innoculated with standard suspension. The primary cultures
took about 3 weeks and sub-cultures 2 weeks to grow on drug free
media. Large sensitive bacillary population required higher concentration
of thioacetazone to inhibit the growth, suggesting standardization
of inoculum size for sensitivity tests. Prolonged incubation
period on drug slopes showed profound influence on the level of
drug inhibiting concentration of thioacetazone; with the increase
in incubation period, fall in growth of sensitive culture
was not observed even on high drug concentration. The reproducibility
of this observation on duplicate specimens from the same patients
after shorter intervals excluded the possibility of experimental
error. A reduction in the inhibition of growth of sensitive organisms
on drug media with time is presumed to be due to either deterioration
of the drugs in the media or due to adaptation by the micro-organisms.
Because of the decrease in inhibition of growth, even sensitive
organisms may be classified as resistant if reading of culture for
drug sensitivity is prolonged beyond 3 weeks of the inoculation
period. It is suggested that a standard inoculum size and a maximum
limit of 3 weeks incubation period should be adopted for finding
out sensitivity to thioacetazone. Cultures classified as sensitive
to the three first line drugs or resistant to one or more, showed
no difference in the pattern of sensitivity to thioacetazone.
|KEY WORDS: INVITRO DRUG SENSITIVITY, M.TUBERCULOSIS,
|UTILITY OF PYRUVATE MEDIUM FOR ISOLATION OF M.BOVIS
AND M.TUBERCULOSIS RESISTANT TO INH
|N Naganathan & R Rajalakshmi: Indian J Med Res
1977, 66, 556-61.
A study was conducted to evaluate the usefulness
of pyruvate medium for isolation of M.bovis from human material
and additional yield of M. tuberculosis resistant to INH. Specimens
from both rural and urban populations were included for this study
in order to understand the problem in both the situations. There
were two studies in progress at the National Tuberculosis Institute
when pyruvate media slopes were introduced for culture purpose.
One study was an epidemiological survey; 2518 sputum specimens received
from 51 villages covering a population of about 32,300 were used.
The specimens were collected from persons aged 5 years and above
showing abnormal shadow on X-ray. The other study was conducted
in collaboration with the State Tuberculosis Centre, Bangalore;
1204 sputum specimens were received from out patients attending
the centre. In addition to LJ medium, pyruvate medium was used for
isolation purposes. Identification and sensitivity tests were done
on positive cultures as per routine. In all, 129 cultures of tubercle
bacilli were isolated from 2118 specimens belonging to study 1 and
398 from 1204 specimens belonging to study 2. The number of cultures
contaminated were 253 and 35 respectively. No M.bovis was
isolated in either study. There were 24 and 23 cultures resistant
to INH among those isolated from LJ and pyruvate medium respectively.
Thus, no increase was observed in the isolation of INH resistant
strains using pyruvate medium.
Hence, no benefit was derived by using this
medium over and above what was obtained from plain Lowenstein Jensen
medium in both the situations.
|KEY WORDS: PYRUVATE MEDIUM, LJ MEDIUM, M.TUBERCULOSIS,
DRUG RESISTANCE, M.BOVIS, RURAL POPULATION, URBAN POPULATION.
|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.
|EFFECT OF CARBON DIOXIDE ON THE PRIMARY ISOLATION
|MM Chauhan, TR Sreenivas & K Chaudhuri: Indian
J TB 1991, 38, 81-85.
The stimulatory effect of carbon dioxide (CO2)
on the growth of tubercle bacilli was reported by a few authors.
A study was done to see the effect of CO2 on primary isolation of
mycobacteria on Lowenstein Jensen medium in terms of (1) positivity
rate (2) improvement in the rate of growth in cultures and (3) contamination
One thousand and five clinical specimens were inoculated,
after processing by modified Petroff's method, onto LJ medium and
incubated with or without addition of 10% of carbon dioxide. Of
the total positive cultures, 30.8% grew only under 10% carbon dioxide
and in 58.3% growth was first seen in that atmosphere. The results
of this study show that (1) 10% carbon dioxide increases the
yield of mycobacteria in primary culture (2) it stimulates the
temporal growth rate resulting in reduction of lag period
by one week (3) the increase in yield is largely from smear negative
specimens and (4) there is no significant increase in the contamination
rate to offset the stimulating effect on mycobacterial growth.
|KEY WORDS: M.TUBERCULOSIS, CARBONDIOXIDE, GROWTH