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Ten catalase-positive isolates and one catalase-negative isolate that had been assigned to Eikenella corrodens were compared to the nomenclatural type strain regarding selected phenotypic and molecular features and chromosomal deoxyribonucleic acid (DNA) relatedness using the spectrophotometric method. Five catalase-positive human isolates were assigned to the genomic species Eikenella corrodens on the basis of high DNA relatedness levels. Three others, among them strain Chen UB 204, exhibited only moderate degrees of DNA relatedness to the type strain and with each other. Two catalase-positive isolates from dogs were closely interrelated, but yielded only low degrees of DNA binding with Eikenella corrodens and the Eikenella-like human isolates. These findings confirm that the human eikenellas comprise more than one genomic species and that the canine strains represent a distinct taxonomic entity. The differentiation of the strains investigated by conventional phenotypic features, hydrolytic enzyme reactions, and cellular carbohydrate patterns was considered.

Summary Selected strains representing established and newly described taxa in the family Pasteurellaceae were investigated for their cellular lipid and carbohydrate composition to clarify the taxonomic significance of such features. Methylated cellular fatty acids and acetylated derivatives of the cellular carbohydrates were determined by capillary gas chromatography using a flame ionization detector. In part the carbohydrates were identified by mass spectrometry. Phospholipids were determined by thin layer chromatography, the lipoquinones by high pressure liquid chromatography. The cellular fatty acid patterns proved to be uniform with minor variations, but the separation from the Neisseriaceae and from Moraxella was possible. Also the distribution of the phospholipids was uniform within the family. The lipoquinone contents were useful for the discrimination of groups within the family not necessarily reflecting the degree of genomic relatedness. The analysis of the cellular carbohydrates resulted in a common sugar pattern with all members of the family and characteristic carbohydrate profiles discriminating groups, often to the species level. All of the cytochemical features considered were useful for the characterization of the family Pasteurellaceae .

The phylogenetic relationships among strains of Pasteurella multocida representing Carter's serogroups A, B, (C), D and E, the type strain (which also represents serogroup A, and biovar 4), the indole-negative strain Schutze HS, and two “dog-type” strains (biovar 6) were investigated by DNA:DNA hybridization using the optical method. The genome DNAs of the “dog-type” strains were almost identical; they displayed, however, only 20 % binding with the DNA of the type strain of P. multocida , and even lower or no measurable binding with the DNAs of the other strains tested. The taxon hitherto classified as biovar 6 of P. multocida is therefore considered as a distinct species; yet the data so far available do not rule out that it belongs to a genus other than Pasteurella sensu stricto . — The remaining strains exhibited high genome DNA relatedness, with between 64 and 98% DNA binding. The present data do not rule out the existence of molecular subspecies in P. multocida .

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.