Characterization of a distinct group of slowly growing mycobacteria by biochemical tests and lipid analyses.

A group of slowly growing mycobacterial strains (n = 14) isolated from respiratory tract specimens was collected from 1971 to 1990 on the basis of growth characteristics and uncommon biochemical and glycolipid profiles. Growth at 25 to 45 degrees C, a negative Tween 80 hydrolysis test, a strong positive reaction in a 14-day arylsulfatase test, and susceptibility to ethambutol in combination with resistance to cycloserine were important for the initial separation. The strains had a distinctive glycolipid pattern which was unlike those of other mycobacterial species. Analyses of cellular fatty acids by gas-liquid chromatography and mycolic acids by thin-layer chromatography further characterized this homogeneous group of mycobacteria. The presence of 2-eicosanol (2-OH-20:0alc) and hexacosanoic acid (26:0) combined with the lack of 2-docosanol (2-OH-22:0alc) differentiated this group from other slowly growing mycobacteria.