|PREVALENCE, FATE, SOURCE AND INFECTIVITY OF RESISTANT
IN MYCOBACTERIUM TUBERCULOSIS
|Raj Narain, P Chandrasekhar, Pyare Lal and RA Satyanarayanachar:
Proceed Natl TB & Chest Dis Workers Conf, Hyderabad,
The material on resistant strains of mycobacterium
tuberculosis is derived from the longitudinal survey conducted from
1961-68 in a random sample of 133 villages of 3 taluks of Bangalore
district. About 54,000 persons aged five years or more were surveyed
3 times at an interval of 18 months, two samples of sputum were
collected from persons whose chest X-rays were judged to have abnormal
shadows. The sputum specimens were examined by direct smear and
culture and sensitivity tests were performed.
An attempt is made to study prevalence, fate, source
and infectivity of resistant mycobacterium tuberculosis in three
rounds. PREVALENCE: In the 3 rounds, 199, 194 and 176 cases
respectively yielded positive cultures; Of them, 30, 36 and 53 cases
were having resistant strains. At round III, the number of culture
positive cases has not fallen significantly, but the number of strains
resistant to INH alone has sharply increased (13, 18 & 35).
Both findings are likely to be due to the treatment with INH alone
offered at round II and also due to the fact that treatment was
taken very irregularly. FATE: Over period of 3 years, of
the cases with INH resistant strains, more than 1/3rd were dead,
1/4th continued to remain positive and resistant, and 1/4th became
culture negative. Whereas, of the cases with strains sensitive to
INH, less than 1/3rd were dead, 1/3rd became negative and the remaining
were positive, 1/2 with sensitive strains and 1/2 with resistant
strains. SOURCE OF CASES: The prevalence of cases with resistant
strains at any one round is not due to the persistence of such cases
from previous rounds but by development of new cases with such strains
at each round. INFECTIVITY: The incidence of infection among
contacts with sensitive strain was significantly more than among
the contacts of cases with resistant strain. It is inferred that
the infectivity of sensitive strains is more than that of the resistant
|KEY WORDS: M.TUBERCULOSIS, SENSITIVE STRAINS,
RESISTANT STRAINS, CASE, FATE, PREVALENCE, INFECTIVITY.
|RESISTANT AND SENSITIVE STRAINS OF MYCOBACTERIUM
TUBERCULOSIS FOUND IN REPEATED SURVEYS AMONG A SOUTH INDIAN RURAL
|Raj Narain, P Chandrasekhar, RA Satyanarayanachar &
Pyare Lal: Bull WHO 1968, 39, 681-99.
The degree of the risk of infection and disease
in man from drug resistant strains of mycobacterium tuberculosis
is not clear. An increase in the prevalence of primary resistance
indicates the extent of such risk while an increase of secondary
or acquired resistance could be considered as a problem of
the individual patient and may reflect limitations of his treatment.
The present report describes the prevalence of
strains with acquired or primary resistance or of sensitive strains
found in 3 successive surveys in a sizable random sample of village
in a south Indian district. Changes in the status of cases with
such strains from one survey to another and their infectivity among
household contacts are also described. The prevalence of tuberculosis
infection among household contacts of cases with acquired resistance
to isoniazid was significantly higher than those with primary resistance
or with sensitive culture. This was probably due to the longer duration
of sputum positivity of isoniazid resistant strains at the time
of diagnosis. But infectivity as judged by the incidence of new
infection among household contacts was generally less for cases
with acquired or primary resistance than for cases with sensitive
cultures, though the difference observed was not statistically significant.
A large number of culture positive cases especially those with primary
resistance had no radiological evidence of active pulmonary tuberculosis.
The prevalence of primary resistance was high in certain categories
of cases and the differences between cases with primary resistance
and those with acquired resistance were many and large. It was suggested
that this could be due to the primary resistant cultures being those
of atypical mycobacteria, despite positivity in the niacin test.
There was a significant increase in the number of cases with acquired
resistance to isoniazid at the third survey owing to the irregular
treatment and supply of INH alone after the second round. The prevalence
of primary resistance at the three rounds was almost the same.
|KEY WORDS: DRUG RESISTANCE, M.TUBERCULOSIS,
RURAL POPULATION, INFECTIVITY, SURVEY.
|INCIDENCE OF TUBERCULOSIS INFECTION IN A SOUTH INDIAN
VILLAGE WITH A SINGLE SPUTUM POSITIVE CASE: AN EPIDEMIOLOGICAL CASE
|MS Krishna Murthy, R Channabasavaiah, AV Nagaraj &
P Chandrasekhar: Indian J TB 1991, 38, 123-30.
During a longitudinal survey, carried out in 119
randomly selected villages of Bangalore district for studying the
time trend of tuberculosis, the average infectivity of a case over
a period of one and a half years was found to be six. In 1986 i.e.,
25 years after the start of I survey, 61 persons belonging to one
village called Nunnur who were found newly infected between I &
II surveys, were interviewed. Further, a general study of the layout
of the houses and public facilities in the village was made. However,
in Nunnur, there was just a single bacteriological case (index case)
identified at the I survey. This index case was resident of household
numbered 80 in the main village. This case study investigates the
background of the observed high infectivity. The incidence rate
of infection in Nunnur was 9.5% in 1½ years which is higher
than the overall average rate of 4% as well as rate for 30 other
single case villages i.e., 3.5%. The investigation reveals that
at least 21 persons., found newly infected at II survey, had varying
levels of contact with the index case. The remaining 40 infected
persons could not be linked, either directly or indirectly, to any
other known bacteriological case including the index case in the
village. All the persons identified as infected at II survey were
distributed throughout the village, beyond the likely zone of infection
of the index case.
|KEY WORDS: SINGLE CASE STUDY, INFECTIVITY, INCIDENCE,
INFECTION, RURAL POPULATION.