Radiometric studies on the oxidation of [1-14C]fatty acids and [U-14C]L-amino acids by mycobacteria.

A radiometric assay system has been used to study oxidation patterns of [1-14C]fatty acids and [U-14C]L-amino acids by drug-susceptible and drug-resistant organisms of the genus Mycobacterium. Two strains of M. tuberculosis susceptible to all drugs, H37Rv TMC 102 and Erdman, were used. Drug-resistant organisms included in this investigation were M. tuberculosis H37Rv TMC 303, M. bovis, M. avium, M. intracellulare, M. kansasii and M. chelonei. The organisms were inoculated into a sterile system containing liquid 7H9 medium along with one of the [1-14C]fatty acids or [U-14C]L-amino acids. Although each individual organism displayed a different pattern of fatty acid oxidation, these patterns were not distinctive enough for identification of the organism. Susceptible and resistant mycobacteria did not display any preferential oxidation of long chain or of short chain fatty acids that might help to distinguish these organisms. As with the fatty acid series, differential oxidation patterns for amino acids could be recognized, but again these patterns were not distinctive enough to identify each organism. Complex amino acids such as proline, phenylalanine and tyrosine were of no use in identification of mycobacteria, since virtually all organisms failed to oxidize them. Identification of each individual organism was feasible using a combination of fatty acids and amino acids which included butyric, octanoic, oleic, glycine and alanine. There was no combination of substrates able to separate susceptible and resistant organisms.