Differentially culturable Mycobacterium tuberculosis in cough-generated aerosols of patients with pulmonary tuberculosis DCTB in cough-generated aerosols

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Introduction. While Mycobacterium tuberculosis cells in sputum in sputum have been studied extensively, little is known of their properties in exhaled aerosols. Hypothesis. As differentially culturable tubercle bacteria (DCTB) are readily found in sputum, we hypothesized that DCTB might also be present in aerosols and potentially contribute to transmission. Aim. To test cough aerosols from recently diagnosed pulmonary tuberculosis (TB) patients for DCTB. Methodology. Cough-generated aerosols and sputum samples were collected from active pulmonary TB patients (n=27). A cough aerosol sampling system was modified to include both an Andersen Cascade Impactor using solid agar and a BioSampler liquid impactor. We performed the most probable number of assays to detect DCTB, using media supplemented with Mycobacterium tuberculosis culture filtrate (CF). Results. Briefly, 63% of patients (n=17) had advanced TB, and 55.6% (n=15) had a 3+ sputum smear for acid-fast bacilli. Evidence for DCTB was found in 8 patients’ aerosols (29.5%) and more than half of the 19 sputum samples tested (n=10; 52.6%). Two patients had DCTB in only one of the collected samples (cough aerosols or sputum). Among cough aerosol specimens, two patients (7%) only had CF-dependent DCTB. Conclusion. We detected DCTB in sputum and evidence for their presence in cough samples from pulmonary TB patients. These data suggest that bacilli undetected by traditional mycobacterial cultures may be aerosolized from pulmonary TB patients.

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