Cough-aerosol cultures of Mycobacterium tuberculosis in the prediction of outcomes after exposure. A household contact study in Brazil

• Published in: PloS one Vol. 13; no. 10; p. e0206384
• Main Authors: Acuña-Villaorduña, Carlos, Schmidt-Castellani, Luiz Guilherme, Marques-Rodrigues, Patricia, White, Laura F, Hadad, David Jamil, Gaeddert, Mary, Ellner, Jerrold J, Fennelly, Kevin P, Palaci, Moises, Dietze, Reynaldo, Jones-López, Edward C
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 29.10.2018; Public Library of Science (PLoS)
• Subjects: Adult; Aerosols; Biology and Life Sciences; Brazil; Cough - microbiology; Culture Techniques; Disease transmission; Female; Housing; Humans; Male; Medicine and Health Sciences; Middle Aged; Mycobacterium tuberculosis; Mycobacterium tuberculosis - growth & development; Mycobacterium tuberculosis - physiology; People and places; Physical Sciences; Predictive Value of Tests; Tuberculosis, Pulmonary - microbiology; Tuberculosis, Pulmonary - transmission; Brazil
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0206384

Mycobacterium tuberculosis cultures of cough-generated aerosols from patients with pulmonary tuberculosis (TB) are a quantitative method to measure infectiousness and to predict secondary outcomes in exposed contacts. However, their reproducibility has not been established. To evaluate the predictive value of colony-forming units (CFU) of M. tuberculosis in cough aerosols on secondary infection and disease in household contacts in Brazil. Adult sputum smear+ and culture+ pulmonary TB cases underwent a standard evaluation and were categorized according to aerosol CFU. We evaluated household contacts for infection at baseline and at 8 weeks with TST and IGRA, and secondary disease. We enrolled 48 index TB cases; 40% had negative aerosols, 27% low aerosols (<10 CFU) and 33% high aerosols (≥10 CFU). Of their 230 contacts, the proportion with a TST ≥10 mm at 8 weeks was 59%, 65% and 75%, respectively (p = 0.34). Contacts of high aerosol cases had greater IGRA readouts (median 4.6 IU/mL, IQR 0.02-10) when compared to those with low (0.8, 0.2-10) or no aerosol (0.1, 0-3.7; p = 0.08). IGRA readouts in TST converters of high aerosol cases (median 20 IU/mL, IQR 10-24) were larger than those from aerosol-negative (0.13, 0.04-3; p = o.o2). 8/9 (89%) culture+ secondary TB cases occurred in contacts of aerosol+ cases. Aerosol CFU predicts quantitatively IGRA readouts among household contacts of smear positive TB cases. Our results strengthen the argument of using cough aerosols to guide targeted preventive treatment strategies, a necessary component of current TB elimination projections.