Detection of Aerosolized Mycobacterium tuberculosis DNA From Adults Being Investigated for Pulmonary Tuberculosis via an Electrostatic Sampler in a South African Primary Care Setting
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Background
Non–sputum-based diagnosis of tuberculosis is a public health priority. Little is known about the feasibility of detecting Mycobacterium tuberculosis (Mtb) complex DNA in respiratory aerosols in primary care, its diagnostic value, and clinical and microbiological characteristics associated with detection.
Methods
We recruited symptomatic adults self-presenting to South African primary care clinics with a sputum Xpert MTB/RIF Ultra (Ultra) result. Cough aerosols were collected on-site by the TB Hotspot Detector, a novel electrostatic aerosol sampler, and tested by Ultra. Environmental and laboratory controls were collected. Predictors of aerosol Mtb DNA (AMD) detection were assessed.
Results
Among 137 participants, 71 (52%) had medium or high sputum Ultra semiquantitative results and 34 (25%) had negative results. When compared with sputum Ultra detection, AMD detection sensitivity and specificity were 46.6% (95% CI, 42.5%–50.7%) and 76.5% (95% CI, 70.4%–82.5%), respectively. Sensitivity was higher in people with a sputum Ultra semiquantitation category of high (56.9%; 95% CI, 51.1%–62.7%). Factors associated with AMD detection were male sex with a sputum Ultra semiquantitative result of medium or greater (adjusted risk ratio, 3.26; 95% CI, 1.11–9.55; P = .024) and a reported fever (adjusted risk ratio, 0.58; 95% CI, .29–1.07; P = .099). Sputum to aerosol ratios were ≥0.75 in 3 participants, suggesting a high capacity to expel Mtb DNA. Despite rigorous decontamination, AMD was detected from 30% of environmental samples, highlighting the TB Hotspot Detector's potent sampling capability and potential nosocomial transmission risks.
Conclusions
Electrostatic aerosol sampling is feasible in primary care to detect people with infectious tuberculosis. Deployment of this and other practical aerosol-sampling tools might help to characterize predictors of tuberculosis transmission.
