title: Cough aerosols of Mycobacterium tuberculosis predict new infection: a household contact study.
abstract: BACKGROUND
  Airborne transmission of Mycobacterium tuberculosis results from incompletely characterized host, bacterial, and environmental factors. Sputum smear microscopy is associated with considerable variability in transmission.
  
  
  OBJECTIVE
  To evaluate the use of cough-generated aerosols of M. tuberculosis to predict recent transmission.
  
  
  METHODS
  Patients with pulmonary tuberculosis (TB) underwent a standard evaluation and collection of cough aerosol cultures of M. tuberculosis. We assessed household contacts for new M. tuberculosis infection. We used multivariable logistic regression analysis with cluster adjustment to analyze predictors of new infection.
  
  
  RESULTS
  From May 2009 to January 2011, we enrolled 96 sputum culture-positive index TB cases and their 442 contacts. Only 43 (45%) patients with TB yielded M. tuberculosis in aerosols. Contacts of patients with TB who produced high aerosols (≥10 CFU) were more likely to have a new infection compared with contacts from low-aerosol (1-9 CFU) and aerosol-negative cases (69%, 25%, and 30%, respectively; P = 0.009). A high-aerosol patient with TB was the only predictor of new M. tuberculosis infection in unadjusted (odds ratio, 5.18; 95% confidence interval, 1.52-17.61) and adjusted analyses (odds ratio, 4.81; 95% confidence interval, 1.20-19.23). Contacts of patients with TB with no aerosols versus low and high aerosols had differential tuberculin skin test and interferon-γ release assay responses.
  
  
  CONCLUSIONS
  Cough aerosols of M. tuberculosis are produced by a minority of patients with TB but predict transmission better than sputum smear microscopy or culture. Cough aerosols may help identify the most infectious patients with TB and thus improve the cost-effectiveness of TB control programs.
authors.affiliation: Section of Infectious Diseases, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, MA 02118, USA. edward.jones@bmc.org
authors.forename: Edward C
authors.initials: EC
authors.lastname: Jones-López
authors.forename: Olive
authors.initials: O
authors.lastname: Namugga
authors.forename: Francis
authors.initials: F
authors.lastname: Mumbowa
authors.forename: Martin
authors.initials: M
authors.lastname: Ssebidandi
authors.forename: Olive
authors.initials: O
authors.lastname: Mbabazi
authors.forename: Stephanie
authors.initials: S
authors.lastname: Moine
authors.forename: Gerald
authors.initials: G
authors.lastname: Mboowa
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Fox
authors.forename: Nancy
authors.initials: N
authors.lastname: Reilly
authors.forename: Irene
authors.initials: I
authors.lastname: Ayakaka
authors.forename: Soyeon
authors.initials: S
authors.lastname: Kim
authors.forename: Alphonse
authors.initials: A
authors.lastname: Okwera
authors.forename: Moses
authors.initials: M
authors.lastname: Joloba
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Fennelly
mesh_terms: D000328:Adult; D000336:Aerosols; D016358:Contact Tracing; D003371:Cough / Q000382:microbiology*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000379:methods; D016015:Logistic Models; D008297:Male; D009169:Mycobacterium tuberculosis / Q000472:pathogenicity*; D011237:Predictive Value of Tests; D013183:Sputum / Q000382:microbiology*; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000150:complications / Q000175:diagnosis / Q000635:transmission*
chemical_list: D000336:Aerosols