Differentiation between Mycobacterium farcinogenes and Mycobacterium senegalense strains based on 16S-23S ribosomal DNA internal transcribed spacer sequences

Abstract

16S ribosomal DNA (rDNA) and 16S-23S internal transcribed spacer rDNA sequence analyses were performed on Mycobacterium farcinogenes and M. senegalense strains and 26 strains of other rapidly growing mycobacteria to investigate the phylogenetic structure of bovine farcy mycobacteria within the M. fortuitum complex. M. farcinogenes and M. senegalense were indistinguishable in their 5"-end 16S rDNA but showed both considerable interspecies spacer sequence divergence and a high level of intraspecies sequence stability. A rapid detection assay using PCR and hybridization with species-specific probes was developed. The assay was specific among 46 species other than M. farcinogenes and M. senegalense and correctly identified all M. farcinogenes and M. senegalense strains. PCR- and 16S-23S rDNA sequence-based detection will be a valuable approach for diagnosis of the causal agents of African bovine farcy in cattle.

FIG. 1.

Comparison of 16S rDNA signature sequences with the respective spacer sequevars. The alignment comprises the two variable regions found in the 5" 16S rRNA genes of selected members of species closely related to M. farcinogenes and M. senegalense. Dots indicate identity, and the corresponding positions of the Escherichia coli 16S rDNA are also shown. nt, nucleotide.

FIG. 2.

Neighbor-joining tree based on sequences derived from 16S-23S rDNA ITS regions showing relationships between M. farcinogenes and M. senegalense and between organisms and representatives of other rapidly growing mycobacterial species. The horizontal lengths represent genetic distances, and the scale bar represents 10% sequence divergence. The values in parentheses are the numbers of strains analyzed (for details, see Table 1). The tree was rooted by using M. tuberculosis as the outgroup.