[Study on species identification of Mycobacteria by gas chromatography analysis of whole-cell fatty acid].

Objective: To evaluate the accuracy and applicability of species identification method of Mycobacteria by applying gas chromatography analysis of whole-cell fatty acid.
Methods: Species identification of 14 reference strains and 727 clinical isolates of Mycobacteria were performed by using MIDI Sherlock Microbial Identification System (MIS)4.0 based on gas chromatography analysis of whole-cell fatty acid, and the results were compared with those of conventional species identification method.
Results: (1) By using the conventional method, all 14 reference strains were identified correctly. Except for Mycobacterium.vaccae, the result obtained by MIS were identical to that of conventional method. (2) Among 625 clinical isolates identified as Mycobacterium tuberculosis (MTB) and Mycobacterium bovis, 45 strains were mistakenly identified as Nontuberculous Mycobacteria (NTM) by MIS. Its accuracy was 93%. For 102 NTM strains, results of group identification showed no difference between the two methods. However, 7 results of species identification were not consistent, the accuracy being 93%. (3) MIS mainly mistook MTB for Mycobacterium gastri, Mycobacterium trivial and Mycobacterium smegmatis, and Mycobacterium scrofulaceum for Mycobacterium gordonae among NTM.
Conclusions: The results of species identification of Mycobacteria by applying gas chromatography analysis of whole-cell fatty acid are in accordance with those of conventional method for the majority of the strains, and MIS can identify Mycobacteria to species level by a single experiment. It can be considered as a good method for species identification of Mycobacteria in terms of its accuracy and applicability.