Vidyya Medical News Service
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Volume 6 Issue 60 Published - 14:00 UTC 08:00 EST 29-Feb-2004 Next Update - 14:00 UTC 08:00 EST 1-Mar-2004
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First direct isolation, quantification, and particle size determination of airborne Mycobacterium tuberculosis aerosols

In its initial issue for March 2004, the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine has published the first report of the direct isolation, quantification, and particle size determination of airborne Mycobacterium tuberculosis aerosols (capable of being cultured), which were generated from the coughs of patients with proven pulmonary tuberculosis (TB).

The investigators developed a cough aerosol sampling system to test 16 subjects with smear-positive pulmonary TB. Cough-generated aerosols were positive in 4 subjects (25 percent).

The authors said that there was a rapid decrease in the cough-generated aerosol cultures within the first 3 weeks of effective treatment. The culture-positive cough aerosols were associated with lack of treatment during the prior week.

The studies were done in the morning before breakfast when patients were asked to provide sputa specimens for clinical purposes. All studies were performed in negative pressure isolation rooms that had six air changes per hour.

No cultured M. tuberculosis was isolated from the room air. Two separate 5-minute air sampling times were chosen with the intent of maximizing aerosol collection and minimizing the discomfort of coughing.

The investigators isolated 633 colony-forming units from the initial aerosol generated by one subject. After one week of treatment, the count dropped to 3 colony-forming units. This finding occurred despite the person's persistently positive smear and cultures.

The authors said that their cough sampling system could be used to study the mechanics of aerosolization of the bacilli from the human respiratory tract, an area of investigation that has received relatively little attention.


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