RESUMO
Context: Despite recent advances in the available diagnostic modalities, diagnosis of pleural tuberculosis remains a challenge because of the low yield of conventional methods. Pleural biopsy is the gold standard for confirmation of diagnosis, which is invasive and cumbersome. The concentration of mycobacterial peptide-specific activated lymphocytes at the site of infection can be utilized as the basis for using IGRA (interferon-gamma release assays) based evaluation of undiagnosed exudative pleural effusions. Aim: To evaluate the performance of IGRA (Enzyme-linked Immunospot (ELISPOT) in pleural fluid for the diagnosis of pleural tuberculosis in histopathologically confirmed cases. Settings and Design: A prospective observational study compared the utility of ELISPOT with thoracoscopy guided pleural biopsies for the diagnosis of tubercular pleural effusions. Methods and Material: Forty-two consecutive cases of undiagnosed pleural effusions were enrolled and subjected to thoracoscopy guided pleural biopsy. Thirteen patients were confirmed to have tuberculosis, 27 had malignancy, and 2 had normal pleura. A total of 1x103 pleural fluid mononuclear cells (PFMCs) were cultured in the presence of early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10) for 24 hours. The individual spots were then counted using an automated analyzer ELISPOT reader system. Results: The number of spots developed in the pleural fluid was significantly higher in tubercular pleural effusions as compared to non-tubercular effusions (CFP-10:154.76±14.61 vs 49.24±8.9; ESAT-6: 150.3±17.27 v/s 45.34±8.23, p<0.001). At a cut-off value of more than 67 spots taken as positive for tuberculosis, the sensitivity of the test was 100% (95% CI 75.29% to 100.00%), specificity was 96.5% (95 % CI 82.24% to 99.91%), positive predictive value was 92.86% (95 % CI 65.45% to 98.89%) and negative predictive value was 100%. Conclusions: ELISPOT can be a useful non-invasive test for the evaluation of undiagnosed pleural effusions and making a diagnosis of pleural tuberculosis with confidence.
RESUMO
A thermophilic fungus Thermomyces la nuginosus, strain IISc 91, secreted one form each of α-amylase and glucoamylase during growth. Both enzymes were purified to homogeneity by ion-exchange and gel-filtration chromatography and obtained in mg quantities. α-Amylase was considered to be a dimeric protein of ~ 42 kDa and contained 5% (by mass) carbohydrate. It was maximally active at pH 5·6 and at 65°C. It had an activation energy of 44 kJ mol–1. The apparent Km for soluble starch was 2·5 mg ml–1. The enzyme produced exceptionally high levels of maltose from raw potato starch. At 50°C, the enzyme was stable for > 7h. At 65°C, α-amylase was nearly 8-times more stable in the presence of calcium. Addition of calcium increaed the melting temperature of α-amylase from 66°C to 73°C. Upon incubation at 94°C, α-amylase was progressively and irreversibly inactivated, and converted into an inactive 72 kDa trimeric species. Glucoamylase was a monomeric glycoprotein of ~ 45 kDa with a carbohydrate content of 11% (by mass). It effected up to 76% conversion of starch in 24 h producing glucose as the sole product. Its apparent Km for soluble starch was 0·04 mg ml–1 and Vmax was 660 μmol glucose min–1 mg protein–1. It also hydrolyzed maltose. Its activity on maltooligosaccharides increased with the chain length of the substrates. Glucoamylase was stable at 60°C for over 7h. Its activation energy was 61 kJ mol–1 Glucoamylase did not show synergistic effect with α- amylase. The properties of α-amylase and glucoamylase of Thermo my ces lanuginosus strain IISc 91 suggest their usefulness in the commercial production of maltose and glucose syrups.