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. 2019 Apr 11;6(6):ofz184.
doi: 10.1093/ofid/ofz184. eCollection 2019 Jun.

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

Carlos Acuña-Villaorduña  1   2 , Irene Ayakaka  3 , Luiz Guilherme Schmidt-Castellani  4 , Francis Mumbowa  5 , Patricia Marques-Rodrigues  4 , Mary Gaeddert  1 , Laura F White  6 , Moises Palaci  4 , Jerrold J Ellner  1 , Reynaldo Dietze  4   7 , Moses Joloba  5 , Kevin P Fennelly  8 , Edward C Jones-López  1
Affiliations

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

Carlos Acuña-Villaorduña et al. Open Forum Infect Dis. .

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.

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Figures

Figure 1.
Figure 1.
Study population and aerosol results in each participating cohort of pulmonary tuberculosis cases patients. Abbreviations: AFB, acid-fast bacilli; CASS, cough aerosol sampling system; HHCs, household contacts.
Figure 2.
Figure 2.
Culturable Mycobacterium tuberculosis colony-forming unit (CFU) count from cough-generated aerosol samples and sputum acid-fast bacilli (AFB) smear grade.
Figure 3.
Figure 3.
A, Culturable aerosol samples and duration of antibiotic therapy before cough aerosol sample collection. B, Sputum acid-fast bacilli (AFB) smear grade and duration of antibiotic therapy before sample collection.
See this image and copyright information in PMC

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