The mechanism of Mycobacterium avium transmission and its definitive reservoir in the environment has not been fully discerned. Most clinicians agree that M. avium enters the body either through the mouth/gastrointestinal tract or through the lungs or both. In the past M. avium has been found in drinking water, institutional shower water and outdoor soil. Recommendations to avoid acquiring infection include avoiding raw foods with possible microscopic contamination with soil, drinking only water that has been heated sufficiently and avoiding oral-fecal contact.
Researchers from UCSF San Francisco General Hospital have published a report in the Journal of Acquired Immunodeficiency Syndromes and Human Retrovirology that links an M. avium source to the soil of indoor potted plants.
Water, food and soil samples were collected from the San Francisco homes of 290 persons with HIV infection. Mycobacteria isolates from those sources were compared with mycobacteria isolates from the participants. M. avium was detected in less than 1% of both food and water samples. However, Mycobacterium avium complex (the infection) was isolated from 55% and Mycobacterium avium itself (the bacteria) was isolated from 27% of soil samples taken from indoor potted plants from the participants' homes. Some of the soil isolates were found to be similar to isolates found in the participants.
The authors conclude that soil from indoor potted plants may be a common source of M. avium in San Francisco. To help prevent transmission from the plant soil, it would be reasonable to wear garden-type or rubber gloves when working with potted plants and wash hands with soap and water after handling plant soil. (See related article on water as a source of Mycobacterium avium in BETA, June 1994, pages 57-58).
Yajko DM and others. Mycobacterium avium complex in water, food, and soil samples collected from the environment of HIV-infected individuals. Journal of Acquired Immunodeficiency Syndromes and Human Retrovirology 9(2): 176-182. June 1995.