|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.