Caracterización fenotípica y genotípica de cepas de Mycobacterium kansasii aisladas en España (2000-2003)

Abstract

Mycobacterium kansasii is an opportunistic pathogen that mainly causes pulmonary infections. This species accounted for 9.7% of Mycobacteria other than tuberculosis complex identified in the reference laboratory of the Spanish Centro Nacional de Microbiologia during the period of 2000-2003. In this study we analyzed the phenotypic and genotypic characteristics of 298 M. kansasii strains isolated over this 4-year period. The phenotypic characteristics were determined by conventional methods: biochemical testing, culture and morphological study. Genotypic characteristics were studied using PCR restriction fragment analysis of a fragment of the hsp65 gene and digestion with BstEII and HaeIII, according to the method of Telenti. Among the total of tested strains, 57.4% had the typical phenotypic characteristics described for M. kansasii. The rest had atypical patterns that we grouped into 17 biotypes. Strains belonging to six of the seven described genotypes were identified, with 86.6% of the strains falling into genotype I. Analysis of the phenotypic characteristics of M. kansasii showed a higher discrimination index for intraspecific differentiation than genotypic methods. Nevertheless, the high variability of phenotypic characteristics, some of which were very specific for the species (e.g., photochromogenicity), could complicate their identification. Hence both conventional and molecular methods should be used to accurately identify the atypical isolates.