Résumé
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.
Résumé
The intranasal route is one of the main routes of Mycobacterium leprae infection and there is paucity of information regarding the mode of spread of the pattern. The adherence of M. leprae to the nasal mucosa, its trapping within the sinuses of the head, and its fate after entry into the host was studied using mouse model. A comparison of the adherence profile of M. leprae and Mycobacterium tuberculosis showed that while larger numbers of M. tuberculosis were demonstrated within lungs, greater numbers of M. leprae were present within the sinuses of the head. Adherence of M. leprae to the nasal mucosa was dependent on surface integrity since opsonization and heat killing resulted in decreased numbers of M. leprae in the nasal sinuses and a greater amount entering the lungs. The adherence appeared to the independent of the viability of the bacilli, as similar numbers of formalin-fixed, rifampicin -treated and viable M. leprae entered the lungs in the initial stages. However the numbers of rifampicin-treated M. leprae in the nasal sinuses were 12-fold lower than the numbers of viable M. leprae. These results indicated that both viability and surface integrity were important in the entry of M. leprae and it's consequent dissemination.