A tuberculosis outbreak from a patient's draining lesion: how did it happen?

1. Mycobacterium tuberculosis can be transmitted from a pulmonary source when droplet nuclei in the 1 to 5 micron range are generated by coughing, singing, or even talking. 2. It is possible for large numbers of droplet nuclei containing M tuberculosis bacteria to be generated during the surgical drainage, débridement, and syringe irrigation of abscesses caused by M tuberculosis. These procedures can produce such a high concentration of droplet nuclei that the ventilation system cannot remove them fast enough to protect the surgical staff from infection. 3. The unrecognized case of tuberculosis is much more likely to be the source of transmission of M tuberculosis than is the individual who has a diagnosis of TB or "rule-out TB." This is because once a diagnosis is known or suspected, interventions are initiated that make the patient less infectious.