Variability of infectious aerosols produced during coughing by patients with pulmonary tuberculosis.
BACKGROUND
Mycobacterium tuberculosis is transmitted by infectious aerosols, but assessing infectiousness currently relies on sputum microscopy that does not accurately predict the variability in transmission.


OBJECTIVE
To evaluate the feasibility of collecting cough aerosols and the risk factors for infectious aerosol production from patients with pulmonary tuberculosis (TB) in a resource-limited setting.


METHODS
We enrolled subjects with suspected TB in Kampala, Uganda and collected clinical, radiographic, and microbiological data in addition to cough aerosol cultures. A subset of 38 subjects was studied on 2 or 3 consecutive days to assess reproducibility.


RESULTS
M. tuberculosis was cultured from cough aerosols of 28 of 101 (27.7%; 95% confidence interval [CI], 19.9-37.1%) subjects with culture-confirmed TB, with a median 16 aerosol cfu (range, 1-701) in 10 minutes of coughing. Nearly all (96.4%) cultivable particles were 0.65 to 4.7 μm in size. Positive aerosol cultures were associated with higher Karnofsky performance scores (P = 0.016), higher sputum acid-fast bacilli smear microscopy grades (P = 0.007), lower days to positive in liquid culture (P = 0.004), stronger cough (P = 0.016), and fewer days on TB treatment (P = 0.047). In multivariable analyses, cough aerosol cultures were associated with a salivary/mucosalivary (compared with purulent/mucopurulent) appearance of sputum (odds ratio, 4.42; 95% CI, 1.23-21.43) and low days to positive (per 1-d decrease; odds ratio, 1.17; 95% CI, 1.07-1.33). The within-test (kappa, 0.81; 95% CI, 0.68-0.94) and interday test (kappa, 0.62; 95% CI, 0.43-0.82) reproducibility were high.


CONCLUSIONS
A minority of patients with TB (28%) produced culturable cough aerosols. Collection of cough aerosol cultures is feasible and reproducible in a resource-limited setting.
Southeastern National Tuberculosis Center, Emerging Pathogens Institute, Room 257, University of Florida, Gainesville, FL 32610, USA. kevin.fennelly@medicine.ufl.edu
Kevin P
KP
Fennelly
Edward C
EC
Jones-López
Irene
I
Ayakaka
Soyeon
S
Kim
Harriet
H
Menyha
Bruce
B
Kirenga
Christopher
C
Muchwa
Moses
M
Joloba
Scott
S
Dryden-Peterson
Nancy
N
Reilly
Alphonse
A
Okwera
Alison M
AM
Elliott
Peter G
PG
Smith
Roy D
RD
Mugerwa
Kathleen D
KD
Eisenach
Jerrold J
JJ
Ellner
D000328:Adult; D000336:Aerosols / Q000032:analysis*; D001431:Bacteriological Techniques; D003371:Cough / Q000382:microbiology*; D003906:Developing Countries; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D010316:Particle Size; D015203:Reproducibility of Results; D012307:Risk Factors; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000382:microbiology* / Q000503:physiopathology / Q000635:transmission; D014454:Uganda
D000336:Aerosols