Detection of Mycobacterium tuberculosis RNA in bioaerosols from pulmonary tuberculosis patients

Bioaerosols from pulmonary tuberculosis (PTB) patients are a quantitative predictor of transmission. Current methods involve sophisticated instruments and time-consuming techniques to assess viable TB bacteria in bioaerosols. We tested the feasibility of detecting Mycobacterium tuberculosis (Mtb) specific RNA from bioaerosols retained on TB patients' masks.

Adult PTB patients (n=33) were recruited at diagnosis before GeneXpert confirmation between April-2017 to February-2019 from private TB clinics in Mumbai. Face mask worn for 1 or 3h or N95 mask containing a cellulose acetate membrane worn for 5min by the patients were tested for the presence of Mtb RNA by quantitative PCR and bacterial load was estimated.

Quantitative PCR targeting rpoB, sigA,16S and fgd1 and sequencing of rpoB confirmed the presence of Mtb specific RNA in mask samples including masks of two patients with unproductive sputum. Membrane samples had seven-fold higher RNA and bacterial load that correlated to bacterial load estimated by sputum GeneXpert.

The study demonstrates that patient masks can be used to sample bioaerosols for detection of viable Mtb. The findings have translational value in the diagnosis of TB and monitoring Mtb variations between and within patients useful for assessing infectiousness and treatment response.