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

Abstract

BackgroundA 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.MethodsWe evaluated the duration of infectiousness of PTB using a retrospective cohort design.ResultsAmong 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).ConclusionThe infectiousness of PTB, under adequate therapy, may persist longer than previously reported, even in patients with non-DR PTB.

Rapid diagnosis of new and relapse tuberculosis by quantification of a circulating antigen in HIV-infected adults in the Greater Houston metropolitan area

“…All culture-positive TB cases in this study had a positive culture sample collected at or following their blood draw. Culture-positivity appears to decline gradually (97%, 93%, 89%, to 83% positivity) over the first 4 weeks of anti-TB treatment [ 29 ], in agreement with other studies [ 30 , 31 ] that indicate that Mtb infectivity can extend 5–6 weeks after standardized anti-TB therapy initiation. However, reduced Mtb abundance in these treated cases still could cause our results to under-report the diagnostic sensitivity of this assay for untreated TB cases.…”

Implementation of multidrug-resistant tuberculosis (MDR-TB) treatment in Gabon: lessons learnt from the field

“…This confirms the necessity of culture for the monitoring of treatment outcome. A similar delay in smear conversion over culture conversion has been reported elsewhere [17] and is probably linked to the presence of dead bacilli hidden in cavities and later on released into the airways. Given that infectiousness is associated with positive sputum culture results and is highest when the smear results are also positive [18], data from our small patient cohort indicate that MDR-TB patients' infectiousness was already reduced by month 2 and reached null by month 3 of treatment (data not shown).…”

Tuberculosis infectious pool and associated factors in East Gojjam Zone, Northwest Ethiopia

“…However, this procedure was less sensitive and unable to identify species. Thus, there might be missing positive cases and considering non- mycobacterium TB species as MTB, which then might affect the size of the infectious period [41]. Alternatively, the infectious period after retreatment initiation was estimated based on recent study findings among MDR-TB patients from the Amhara Region, Ethiopia [11, 14, 34].…”

“…1) including the factors associated with the paths. However, the accurate estimation of the magnitude of the PTB infectious pool would not be easy in the real world [41]. Therefore, we think, this study may provide better information in estimating TB infectious pool and be helpful for PTB control.…”