Aerosolization of <i>Mycobacterium tuberculosis</i> by Tidal Breathing.

Abstract

<b>Rationale:</b> Interrupting tuberculosis (TB) transmission requires an improved understanding of how and when the causative organism, <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>), is aerosolized. Although cough is commonly assumed to be the dominant source of <i>Mtb</i> aerosols, recent evidence of cough-independent <i>Mtb</i> release implies the contribution of alternative mechanisms. <b>Objectives:</b> To compare the aerosolization of <i>Mtb</i> bacilli and total particulate matter from patients with TB during three separate respiratory maneuvers: tidal breathing (TiBr), FVC, and cough. <b>Methods:</b> Bioaerosol sampling and <i>Mtb</i> enumeration by live-cell, fluorescence microscopy were combined with real-time measurement of CO₂ concentration and total particle counts from 38 patients with GeneXpert-positive TB before treatment initiation. <b>Measurements and Main Results:</b> For all maneuvers, the proportions of particles detected across five size categories were similar, with most particles falling between 0.5-5 μm. Although total particle counts were 4.8-fold greater in cough samples than either TiBr or FVC, all three maneuvers returned similar rates of positivity for <i>Mtb</i>. No correlation was observed between total particle production and <i>Mtb</i> count. Instead, for total <i>Mtb</i> counts, the variability between individuals was greater than the variability between sampling maneuvers. Finally, when modelled using 24-hour breath and cough frequencies, our data indicate that TiBr might contribute more than 90% of the daily aerosolized <i>Mtb</i> among symptomatic patients with TB. <b>Conclusions:</b> Assuming the number of viable <i>Mtb</i> organisms released offers a reliable proxy of patient infectiousness, our observations imply that TiBr and interindividual variability in <i>Mtb</i> release might be significant contributors to TB transmission among active cases.