Risk factors associated with MDR-TB at the onset of therapy among new cases registered with the RNTCP in Mumbai, India.

Background: Multidrug - resistant TB (MDR - TB) has emerged as a major threat to global TB control efforts in recent years. Facilities for its diagnosis and treatment are limited in many high - burden countries, including India. In hyper - endemic areas like Mumbai, screening for newly diagnosed cases at a higher risk of acquiring MDR - TB is necessary, for initiating appropriate and timely treatment, to prevent its further spread. Objective: To assess risk factors associated with MDR - TB among Category I, new sputum smear-positive cases, at the onset of therapy. Materials and Methods: The study applied an unmatched case - control design for 514 patients (106 cases with MDR - TB strains and 408 controls with non - MDR - TB strains). The patients were registered with the Revised National Tuberculosis Control Program (RNTCP) in four selected wards of Mumbai during April 2004 - January 2007. Data were collected through semi - structured interviews and drug susceptibility test results. Results: Multivariate analysis indicated that infection with the Beijing strain (OR = 3.06; 95% C.I. = 1.12 - 8.38; P = 0.029) and female gender (OR = 1.68; 95% C.I. = 1.02 - 2.87; P = 0.042) were significant predictors of MDR-TB at the onset of therapy. Conclusion: The study provides a starting point to further examine the usefulness of these risk factors as screening tools in identifying individuals with MDR-TB, in settings where diagnostic and treatment facilities for MDR-TB are limited.

Importance of blood samples for diagnosis and drug sensitivitytesting in HIV positive patients with suspected tuberculosis.

Background: Diagnosis of tuberculosis is difficult in HIV positive patients since they often present with atypical symptoms and are susceptible to pulmonary infections that mimic tuberculosis. Sputum collection may not be possible even in patients with pulmonary involvement since a productive cough is not always present. In such patients, blood smear and culture for AFB apart from serving as a diagnostic tool can be used for testing drug sensitivity. Objectives: This study was undertaken to explore the value of blood culture for diagnosis in patients with suspected TB. In addition, a comparison of drug sensitivity patterns of blood and sputum isolates in 10 of these patients was also carried out. Methods: Blood and sputum samples were processed, cultured and isolates tested for their drug susceptibility and for niacin production, nitrate reduction as well as catalase activity at 68o C. Results: All 24 blood samples were culture positive although only 6 were smear positive. On the basis of the biochemical investigations, 22 strains were identified as Mycobacterium tuberculosis. All the 10 sputum samples were culture positive despite 4 being smear negative. Comparison of drug sensitivity profiles from blood and sputum revealed concordance to five first or second line drugs in 5 of 10 patients. Additionally, 2 patients demonstrated discordance for only one first or second line drug. Conclusion: The study demonstrates the importance of blood culture in confirming diagnosis of tuberculosis and testing for drug sensitivity in HIV positive patients without a productive cough. The level of discordance in drug sensitivity profiles between blood and sputum the same individual is suggestive of infection with multiple strains. Testing for the occurrence of multistrain infections through individual colony examination of a single isolate is necessary since such infections would affect treatment of non-responder patients having HIV-TB dual infections.