Mycobacterium avium-intracellulare in clinical specimens: etiological factor or contaminant?

The Mycobacterium avium-intracellulare (MAI) group comprised 10.5% of all nontuberculous mycobacteria isolated in the Mycobacterium Reference Laboratory, Tel Aviv, in an 11-year study period. From the Buirej Chest Hospital in Gaza, alone, 273 strains were isolated, representing 12.1% of the specimens from that hospital, while 149 strains (0.24% of all specimens) were isolated from all other institutions. Pulmonary disease was attributed to this organism in 22 patients, 17 of whom were hospitalized (initially for tuberculosis or another lung disease) in Buirej Hospital. The water was thought to be the source of contamination, since MAI strains, similar to those found in sputum, were isolated from it. In 1985, the water system was renovated and the MAI incidence in sputum from this hospital consequently declined.