Genomic relationships and species differentiation in the genus Capnocytophaga

Ten epidemiologically independent Capnocytophaga strains from clinical materials constituted three distinct DNA homology groups corresponding to the established species, Capnocytophaga ochracea, sputigena, and gingivalis. The three groups exhibited only low, or even insignificant degrees of genomic relatedness mutually, and to a reference culture of CDC group DF-2. All of five Capnocytophaga ochracea strains considered were involved in topic infections whereas four strains, isolated from blood belonged to either Capnocytophaga sputigena or Capnocytophaga gingivalis. However, Capnocytophaga ochracea and Capnocytophaga sputigena could not be discriminated on the basis of DNA base composition, genome size, or phenotypic features including cellular fatty acids, lipoquinones, and various fermentation and hydrolase reactions. The need for additional phenotypic criteria characterizing species of Capnocytophaga is underlined by the present findings.