Background/aims: Culture-difficult bacteria, including asaccharolytic anaerobic gram-negative coccobacilli (AAGNC), may constitute a predominant group of organisms in oral sites. This study aimed to characterize phylogenetically 10 AAGNC isolated from endodontic lesions and periodontal pockets. Methods: 16S rDNA sequence and G + C content were determined. Strains sharing more than 98% sequence similarities and similar G + C content were considered the same bacterial species. Results: One isolate resembled Dialister pneumosintes (the type species of the genus Dialister) with 35 mol% G+C content and 97% sequence similarity. Of eight isolates having 45-47 mol% G+C content, seven were identified as D. invisus and one resembled Dialister invisus with 97% sequence similarity. However the 16S rDNA sequence similarities with D. pneumosintes were relatively low, indicating the strains may belong to a new genus. The last isolate revealed 35 mol% G+C content, but had higher 16S rDNA sequence similarity with D. invisus than with D. pneumosintes. Conclusion: The group of oral AAGNC isolates need to be reclassified.
- Asaccharolytic anaerobic gram-negative anaerobic coccobacilli, AAGNC
- Dialister invisus
- Dialister pneumosintes
- Gram-negative anaerobic coccobacilli
- Phylogenetic characterization