Ralstonia paucula (formerly CDC group IV c-2): Unsuccessful strain differentiation with PCR-based methods, study of the 16S-23S spacer of the rRNA operon, and comparison with other Ralstonia species (R-eutropha, R-pickettii,R-gilardii, and R-solanacearum)

Ralstonia paucula (formerly CDC group IV c-2) can cause serious human infec tions. Confronted in 1995 with five cases of nosocomial bacteremia, we foun d that pulsed-field gel electrophoresis could not distinguish between the i solates and that randomly amplified polymorphic DNA analysis was poorly dis criminatory. In this study, we used PCR-ribotyping and PCR-restriction frag ment length polymorphism analysis of the spacer 16S-23S ribosomal DNA (rDNA ); both methods were unable to differentiate R. paucula isolates. Eighteen strains belonging to other Ralstonia species (one R. eutropha strain, six R . pickettii strains, three R. solanacearum strains, and eight R. gilardii s trains) were also tested by PCR-ribotyping, which failed to distinguish bet ween the four species. The 16S-23S rDNA intergenic spacer of R. paucula con tains the tRNA(Ile) and tRNA(Ala) genes, which are identical to genes descr ibed for R. pickettii and R. solanacearum.