Comparison of a new insertion element, IS1407, with established molecular markers for the characterization of Mycobacterium celatum.

Abstract

Genomic analyses of 18 Mycobacterium celatum strains obtained from different patients in three countries (United States, United Kingdom, and France) were performed; the methods used in this study were restriction fragment length polymorphism (RFLP) analysis, pulsed-field gel electrophoresis (PFGE) analysis, and PCR restriction analysis (PRA) of the hsp-65 gene. A new insertion sequence, IS1407 (GenBank accession no. X97307), belonging to the IS256 family, was identified in M. celatum type 1 strains and was characterized by sequencing. When a probe for Mycobacterium xenopi IS1395-like sequences was used, the RFLP analysis of M. celatum type 1 strains revealed that they contained three or four copies of IS1407 in identical genomic positions, while this element was absent in all M. celatum type 2 strains. PFGE performed with three different endonucleases revealed a unique large restriction fragment (LRF) pattern for M. celatum type 1 strains, whereas the LRF patterns obtained for M. celatum type 2 strains were polymorphic. Moreover, PFGE of nondigested genomic DNA revealed extrachromosomal elements in M. celatum type 2. The type strain of M. celatum type 3 could not be differentiated from M. celatum type 1 strains on the basis of the results of the RFLP analysis, the PFGE analysis, and the PRA of IS1407. In this study we confirmed that M. celatum types 1 and 2 represent distinct genomic clusters and that the molecular markers in M. celatum type 2 exhibit greater polymorphism than the molecular markers in M. celatum type 1.