Gas chromatography-mass spectrometry of mycolic acids as a tool in the identification of medically important coryneform bacteria.

The mycolic acid derivatives of 11 unidentified pathogenic coryneform bacteria were examined by TLC, GLC and GLC-mass spectrometry. The resulting mycolic acid profiles of the unidentified isolates were compared with those of type or reference strains of possibly related coryneform species, namely Corynebacterium bovis, C. diphtheriae, C. xerosis and Rhodococcus equi. It was apparent that most of the unidentified strains showed a distinctive mycolic acid profile, with predominant amounts of relatively high molecular weight mycolic acids (C32-C36) and a high degree of unsaturation, and could thus be distinguished from both C. bovis, which had exceptionally low molecular weight mycolic acids (C24-C30), and C. diphtheriae (C28-C34), which had large amounts of saturated mycolic acids. The mycolates of C. xerosis and R. equi (C28-C36) were generally similar to those of the unidentified coryneforms but their overall mycolic acid patterns were different from one another as well as the unidentified strains. The mycolic acid profiles exhibited by the pathogenic coryneforms examined here were very similar to one another but unlike that of any of the type or reference strains included in the study.