[Exhaled breath-generated aerosols of mycobacterium tuberculosis in patients with active pulmonary tuberculosis...

It has been understood that cough-generated aerosols act as an important vector for the spread of pulmonary tuberculosis. Humans commonly exhale aerosols during the normal respiration process that contain small droplets of the airway lining fluid. We aimed to determine whether aerosols exhaled by active pulmonary tuberculosis (AP-TB) patients may contain droplets with Mycobacterium tuberculosis (M-TB) during normal breathing.

Preliminarily, the collection efficiency of M-TB that was suspended in normal saline or distilled water was examined after subjecting the suspension to centrifugation at 3,000 g for 20 minutes. Better collection efficiency was observed in case of M-TB suspended in distilled water than that suspended in normal saline after centrifugation. Therefore, we selected distilled water instead of normal saline to prepare the fluid that was bubbled with exhaled breath. AP-TB patients with smear positive pulmonary tuberculosis who were being treated with anti-TB drugs for less than 7 days or those before the initiation of therapy expired into a 50-ml tube containing 10 ml distilled water for 30 minutes. We also prepared an exhaled breath condensate by cooling exhaled air through the tubing apparatus.

In case of 20 AP-TB patients, the distilled water bubbled with the exhaled breath were negative for M-TB on smear, culture, and PCR (polymerase chain reaction) detection methods. The exhaled breath condensates were also negative in 24 AP-TB patients.

These results suggest that exhaled breath-generated aerosols from AP-TB patients during normal breathing do not act as a vector for the spread of pulmonary tuberculosis.