Preliminary study using species-specific oligonucleotide probe for rRNA of Bilophila wadsworthia

Portions of the 16S RNA from a urease-positive Bilophila wadsworthia strain were sequenced, and a probe was constructed. The probe was end labeled with [32P]ATP and polynucleotide kinase and hybridized on a nylon filter (by dot blot hybridization) to the immobilized rRNA of 12 B. wadsworthia strains and eight other anaerobic isolates. The probe efficiently hybridized only to the Bilophila strains. Cross-reactivity at high RNA levels (2,000 ng) was observed with one strain of Bacteroides thetaiotamicron and one strain of Bacteroides fragilis (with 10x SET buffer [20x SET buffer is 0.5 M NaCl, 0.03 M Tris, and 2 mM EDTA]) but was not seen at lower RNA levels or with 5x SET buffer. When tested against mixed cultures of aerobic and anaerobic isolates representative of appendiceal abscess flora, the probe did not react with mixed cultures containing no Bilophila cells and could detect > or = 10(5) Bilophila CFU/ml when the mixture was seeded with Bilophila cells. This probe is of potential use in the rapid identification of pure isolates and in the direct identification of B. wadsworthia in clinical specimens.