title: Detection of Mycobacterium tuberculosis in bronchial washing of smear-positive patients after sputum conversion.
abstract: The main purpose of chemotherapy of tuberculosis is to ensure the noninfectiousness of patients with active pulmonary tuberculosis. For this reason, the sputum of smear-positive pulmonary tuberculosis patients is examined at the end of the first and second month of therapy to determine the conversion rate, which is expected to be 85% at the end of the second month. The patients whose sputum has converted to smear-negative are considered noninfectious. The aim of this study was to challenge the theory that negative sputum smear test results always indicate the absence of Mycobacterium tuberculosis bacilli in respiratory secretions from patients with active pulmonary tuberculosis after treatment. In order to achieve this goal, 46 patients with pulmonary tuberculosis whose sputum was positive for M. tuberculosis at the first visit were followed until they gave two consecutive negative smears. The bronchoalveolar lavage fluid of these patients was then examined for M. tuberculosis bacilli. It was observed that eight (17.5%) and five (10%) of these patients, who had already undergone sputum conversion, gave positive smear and culture results respectively. It could be concluded that a negative sputum result is not an appropriate index for evaluating the infectiousness of patients with pulmonary tuberculosis, and, since a few Mycobacterium tuberculosis bacilli can cause tuberculosis, especially in an immunocompromised host, it is mandatory that complementary studies to assess the transmission and virulence of Mycobacterium tuberculosis bacilli after sputum conversion be conducted.
authors.affiliation: National Research Institute of Tuberculosis and Lung Disease, Darabad, Tehran, Iran.
authors.forename: M R
authors.initials: MR
authors.lastname: Masjedi
authors.forename: H R
authors.initials: HR
authors.lastname: Jamaati
authors.forename: F K
authors.initials: FK
authors.lastname: Amin
authors.forename: A A
authors.initials: AA
authors.lastname: Velayati
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*