The limitation of microscopy, culture and radiology in the diagnosis of tuberculosis, especially smear negative and extra pulmonary, are well known. Hence, attempts have been going on to find a suitable serodiagnostic test. One such test was based on Kaolin Agglutination using tuberculo phosphatide as antigen. A study was done to find out the usefulness of this test in the diagnosis of pulmonary tuberculosis. Serum specimens from 297 newly diagnosed tuberculosis patients and 208 healthy controls, were subjected to Kaolin Agglutination Test (KAT) using tuberculo phosphatide as antigen. Of the 297 X-ray positives, 184 were sputum smear positive and 237 were culture positive for M.tuberculosis. A titre of >= 16 was taken to be diagnostic.

The test picked up 53.6 percent of the culture positives and 54.0 percent of the microscopy positives correctly. Also, 48.8 percent of the X-ray positives and 14.2 percent of the healthy controls were found positive. The overall sensitivity of KAT was 53.6 percent and specificity 85.8 percent which does not make the test suitable for diagnosis of tuberculosis.

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 rate.

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.

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.

Non-tuberculous Mycobacteria (NTM) that are present in the environment are responsible for induction of non-specific tuberculin sensitivity. They not only interfere with the results of tuberculin surveys, but are reported to influence the protective effect of BCG also. The prevalence and species distribution of NTM varies from place to place.

A study was carried out to find out the prevalence and identification of predominant species of NTM from the sputum specimens collected from chest symptomatics during an epidemiological survey in rural population of Bangalore district. Sputum specimens collected from 4015 tuberculin positive chest symptomatic persons were subjected for microscopy and culture for mycobacteria. Of the total 145 (3.6%) specimens showed growth of acid fast bacilli. Of them, 44 (30.3%) were M.tuberculosis and remaining 101 (69.7%) cultures were NTM. Specieswise distribution of NTM was as follows: 48% rapid growers, 26% scotochromogens and 22% non-chromogens. Most frequently isolated species were M.phlei (16.7%), M.gordonae (13.3%) and M.scrofulaceum. M.avium complex, M.xenopi, M.fortuitum complex and M.chelonei complex constituted 3.3% each.