Host Determinants of Infectiousness in Smear-Positive Patients With Pulmonary Tuberculosis

Abstract

Background Epidemiologic data suggests that only a minority of tuberculosis (TB) patients are infectious. Cough aerosol sampling is a novel quantitative method to measure TB infectiousness. Methods We analyzed data from three studies conducted in Uganda and Brazil over a 13-year period. We included sputum acid fast bacilli (AFB) and culture positive pulmonary TB patients and used a cough aerosol sampling system (CASS) to measure the number of colony-forming units (CFU) of Mycobacterium tuberculosis in cough-generated aerosols as a measure for infectiousness. Aerosol data was categorized as: aerosol negative (CFU = 0) and aerosol positive (CFU > 0). Logistic regression models were built to identify factors associated with aerosol positivity. Results M. tuberculosis was isolated by culture from cough aerosols in 100/233 (43%) TB patients. In an unadjusted analysis, aerosol positivity was associated with fewer days of antituberculous therapy before CASS sampling (p = .0001), higher sputum AFB smear grade (p = .01), shorter days to positivity in liquid culture media (p = .02), and larger sputum volume (p = .03). In an adjusted analysis, only fewer days of TB treatment (OR 1.47 per 1 day of therapy, 95% CI 1.16-1.89; p = .001) was associated with aerosol positivity. Conclusion Cough generated aerosols containing viable M. tuberculosis, the infectious moiety in TB, are detected in a minority of TB patients and rapidly become non-culturable after initiation of antituberculous treatment. Mechanistic studies are needed to further elucidate these findings.

Contact investigation of tuberculosis in Brunei Darussalam: Evaluation and risk factor analysis

“…Also, contacts of smear positive PTB cases have been previously reported as having higher risk of LTBI diagnosis 8 ; cough aerosol experiments have showed smear positive PTB cases as a risk factor of infectiousness. 22 Despite foreign nationals constituting 16.2% of the total contact population in our study, their percentage of LTBI diagnosis (13.4%) was higher when compared with that of the locals (9.4%). This indicates that foreign nationals Open access Open access…”

“…Foreign residents,17 18 household contacts18–20 and male gender20 21 have previously been shown to be at increased risk of LTBI diagnosis. Also, contacts of smear positive PTB cases have been previously reported as having higher risk of LTBI diagnosis8; cough aerosol experiments have showed smear positive PTB cases as a risk factor of infectiousness 22…”

Contact investigation of tuberculosis in Brunei Darussalam: Evaluation and risk factor analysis

“…Foreign residents [17, 18], household contacts [18–20], and male gender [20, 21] have previously been shown to be at increased risk of LTBI diagnosis. Also, contacts of smear positive PTB cases have been previously reported as having higher risk of LTBI diagnosis [8]; cough aerosol experiments have showed smear positive PTB cases as a risk factor of infectiousness [22].…”

SLeuthing Tuberculous Cough

“…Cough is a major feature of tuberculosis (TB), and epidemiologic studies suggest that it is a predictor of TB transmission (Turner et al, 2018). In contrast to some lung infections in which cough lasts for weeks after infection is cleared, cough in tuberculosis decreases rapidly after initiation of treatment, as does contagion (Acuñ a-Villaorduñ a et al, 2019;Proañ o et al, 2017). Yet, lung damage and live M. tuberculosis can persist for weeks to months.…”