Duration of Pulmonary Tuberculosis Infectiousness under Adequate Therapy, as Assessed Using Induced Sputum Samples

• Published in: Tuberculosis and respiratory diseases 2017-01, Vol.80 (1), p.27-34
• Main Authors: Ko, Yousang, Shin, Jeong Hwan, Lee, Hyun-Kyung, Lee, Young Seok, Lee, Suh-Young, Park, So Young, Mo, Eun-Kyung, Kim, Changhwan, Park, Yong Bum
• Format: Article
• Language: Korean
• Subjects: Pulmonary; Mycobacterium tuberculosis; Infectious Disease Incubation Period; Induced Sputum; Tuberculosis
• ISSN: 1738-3536; 2005-6184

Background: A sputum culture is the most reliable indicator of the infectiousness of pulmonary tuberculosis (PTB); however, a spontaneous sputum specimen may not be suitable. The aim of this study was to evaluate the infectious period in patients with non-drug-resistant (DR) PTB receiving adequate standard chemotherapy, using induced sputum (IS) specimens. Methods: We evaluated the duration of infectiousness of PTB using a retrospective cohort design. Results: Among the 35 patients with PTB, 22 were smear-positive. The rates of IS culture positivity from baseline to the sixth week of anti-tuberculosis medication in the smear-positive PTB group were 100%, 100%, 91%, 73%, 36%, and 18%, respectively. For smear-positive PTB cases, the median time of conversion to culture negativity was 35.0 days (range, 28.0-42.0 days). In the smear-negative PTB group (n=13), the weekly rates of positive IS culture were 100%, 77%, 39%, 8%, 0%, and 0%, respectively, and the median time to conversion to culture-negative was 21.0 days (range, 17.5-28.0 days). Conclusion: The infectiousness of PTB, under adequate therapy, may persist longer than previously reported, even in patients with non-DR PTB.