The Comparison between Two Methods for Typing of Nontuberculous Mycobacteria: High Pressure Liquid Chromatography and Molecular Assay Genotype Mycobacterium CM/AS

Introduction: The GenoType Mycobacterium CM and the GenoType Mycobacterium AS (HAIN Lifescience, Germany) were evaluated for the ability to differentiate mycobacterial species of clinical isolates. Serial use of the both assays is aimed to identify 38 different molecular patterns, of which 24 patterns can be assigned to single species, 10 patterns are allocated to two or more Mycobacterium species, and 4 patterns correspond to Mycobacterium species and gram-positive bacteria with a high G + C content. The analysis of mycolic acids by high pressure liquid chromatography (HPLC) was the reference method. Materials and methods: A set of 127 nontuberculous mycobacterial isolates on Loewenstein-Jensen media, derived from different patients between 1999 and 2007, was analyzed. The strains were primary classified by HPLC following the diagnostic procedure, and retyped by GenoType Mycobacterium CM/AS. Results: In total, results obtained by both methods were interpretable for 113 strains. Concordant results were obtained for 105 (93%) mycobacterial strains. One out of 8 incorcondantly classified strains, which was classified as M. abscessus/M. chelonae by HPLC, displayed a pattern of M. tuberculosis complex by a molecular method. Eleven clinical strains were differentiated only by one of used methods, either by HPLC (6 strains) or by GenoType CM/AS (5 strains). Three strains were not classified at all. Conclusions: Our results show that the GenoType Mycobacterium CM/AS system represents a useful tool to identify mycobacterial clinical isolates. The molecular system is as rapid and reliable as the HPLC, but much easier to perform and more friendly for the environment.