# Detection of Aerosolized Mycobacterium tuberculosis DNA From Adults Being Investigated for Pulmonary Tuberculosis via an Electrostatic Sampler in a South African Primary Care Setting

## TL;DR

The study shows that electrostatic sampling can detect tuberculosis DNA in aerosols from patients in primary care, offering a new way to assess infectiousness.

## Contribution

The study introduces a novel electrostatic sampler for detecting Mycobacterium tuberculosis DNA in aerosols in a primary care setting.

## Key findings

- Electrostatic sampling detected Mtb DNA in 46.6% of cases with high sensitivity in those with high sputum results.
- AMD detection was associated with male sex and reported fever.
- Environmental samples showed Mtb DNA detection, indicating potential transmission risks.

## Abstract

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.

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.

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.

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.

Collecting aerosol from people investigated for tuberculosis in primary care is challenging. Using electrostatic sampling, we detected Mycobacterium tuberculosis DNA from 48 (46%) of 103 people diagnosed with tuberculosis. This approach could facilitate better at-scale characterization of infectiousness in diverse settings.