Evaluation of a simple method for growing Mycobacterium haemophilum.

Surface paper strips containing hemin (X factor) were tested on Middlebrook 7H10 agar and Lowenstein-Jensen medium to determine if the growth requirement of Mycobacterium haemophilum for iron-containing complexes could be met by this simplified method. One reference strain and seven strains of this species isolated from patients showed good growth around the strips on 7H10 within 2 weeks but failed to grow on Lowenstein-Jensen medium with X-factor strips. Middlebrook 7H10 medium with X-factor strips may be a useful alternative to the preparation of specialized media for the recovery of M. haemophilum from clinical specimens.

Mycobacterium celatum sp. nov.

A new slowly growing nonphotochromogenic Mycobacterium species of clinical importance is described. The biochemical characteristics of this organism were similar to those of Mycobacterium xenopi and members of the Mycobacterium avium complex. However, none of the strains reacted with commercially available genetic probes for the M. avium complex. The strains were resistant to most antituberculosis drugs. Multilocus enzyme electrophoresis revealed two original electrophoretic types, which was suggestive of new species. The strains contained alpha-, keto-, and dicarboxylic mycolates, as determined by thin-layer chromatography. A mycolic acid analysis by high-performance liquid chromatography revealed a chromatographic pattern similar to that of M. xenopi, but distinct from the patterns of previously described Mycobacterium species. Hexadecanoic and tuberculostearic acids were identified as the major cell wall fatty acids by gas-liquid chromatographic analysis; hexacosanoic acid was the major mycolic acid cleavage product, and 2-eicosanol was the major alcohol. Evaluation of the 16S rRNA sequence confirmed the phylogenetic position of the organism among the slowly growing Mycobacterium species. Cultures representing this new species have been deposited in the American Type Culture Collection as strains ATCC 51130 and ATCC 51131T (T = type strain). The name Mycobacterium celatum is proposed.