[Identification of Capnocytophaga species by microplate hybridization method, and its restriction endonuclease...

Because differentiation of Capnocytophaga on a species level has been reportedly proved impossible, we used a microplate hybridization method to identify three Capnocytophaga species. Photobiotin labeled DNAs from clinical isolates were added to the wells of a microdilution plate in which reference DNA had been immobilized. After 2 h of hybridization at 40 degrees C, hybridized DNAs were quantitatively detected with peroxidase-conjugated streptavidin and the substrate, tetramethylbenzidine. Of the 22 strains of Capnocytophaga species, 6 strains were identified as C. sputigena, 8 strains as C. gingivalis, and 8 strains as C. ochracea. Genomic DNAs from 25 strains of Capnocytophaga were treated with restriction endonuclease of HindIII, HaeIII, and HinfI. Nine strains of C. gingivalis showed no bands by the conventional electrophoresis of digested DNA. However, twelve strains (6 strains of C. sputigena and 6 strains of C. ochracea) revealed bands by the electrophoresis of HinfI-digested DNA, and ten isolates had its own digestion patterns, indicating the presence of genetic variation. On the other hand, two strains of beta-lactamase-producing C. ochracea, one from blood and one from throat swabs obtained from a patient with acute leukemia, were classified as the same isolate by the identical digestion pattern and by the antimicrobial susceptibility test results, which strongly suggested that the oral lesion is the portal of entry into the blood.