Characterization of Mycobacterium bohemicum isolated from human, veterinary, and environmental sources

Chemotaxonomic and genetic properties were determined for 14 mycobacterial isolates identified as members of a newly described species Mycobacterium b ohemicum. The isolates recovered from clinical, veterinary, and environment al sources were compared for lipid composition, biochemical test results, a nd sequencing of the 16S ribosomal DNA (rDNA) and the 16S-23S rDNA internal transcribed spacer (ITS) regions. The isolates had a lipid composition tha t was different from those of other known species. Though the isolates form ed a distinct entity, some variations were detected in the features analyze d. Combined results of the phenotypic and genotypic analyses were used to g roup the isolates into three clusters, The major cluster (cluster A), very homogenous in all respects, comprised the M. bohemicum type strain, nine cl inical and veterinary isolates, and two of the five environmental isolates. Three other environmental isolates displayed an insertion of 14 nucleotide s In the ITS region; they also differed from cluster A in fatty alcohol com position and produced a positive result in the Tween 80 hydrolysis test. Am ong these three, two isolates were identical (cluster B), but one isolate ( cluster C) had a unique high-performance liquid chromatography profile, and its gas liquid chromatography profile lacked 2-octadecanol, which was pres ent in all other isolates analyzed, Thus, sequence variation in the 16S-23S ITS region was associated with interesting variations in lipid composition . Two of the isolates analyzed were regarded as potential inducers of human or veterinary infections. Each of the environmental isolates, ail of which were unrelated to the cases presented, was cultured from the water of a di fferent stream, Hence, natural waters are potential reservoirs of M. bohemi cum.