Capnophilic Bird Pathogens in the Family Flavobacteriaceae: Riemerella, Ornithobacterium and Coenonia
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Capnophilic Bird Pathogens in the Family Flavobacteriaceae: Riemerella, Ornithobacterium and Coenonia P. VANDAMME, H. M. HAFEZ AND K. H. HINZ
Introduction Riemerella columbina, Ornithobacterium rhinotracheale and Coenonia anatina were initially recognized in the course of long-term studies on the etiology of respiratory tract infections in birds as phenotypically unusual isolates. The reclassification of the organism known as Pasteurella anatipestifer and Moraxella anatipestifer (Segers et al., 1993) triggered a series of taxonomic studies leading to the stepwise characterization and description of O. rhinotracheale (Vandamme et al., 1994), C. anatina (Vandamme et al., 1999) and R. columbina (Vancanneyt et al., 1999). There have been no additional studies since the original description of the latter two organisms. However, the formal description of O. rhinotracheale led to a wealth of studies on this bacterium because of its recognition as an economically important pathogen in turkey and chicken husbandry. Rather unexpectedly, although not closely related, Riemerella, Ornithobacterium and Coenonia turned out to belong to the same major phylogenetic lineage, now known as the family Flavobacteriaceae (Bernardet et al., 1996).
Taxonomy Overview This group of capnophilic bird pathogens comprises four species. Within the genus Riemerella, R. anatipestifer is the type species with R. columbina as a second species. Ornithobacterium rhinotracheale and C. anatina are the type and only species of their respective genera. Riemerella anatipestifer has been isolated worldwide from domestic and wild birds. The organism causes a disease named “exudative septicemia” (Riemer, 1904), which particularly affects ducks, less frequently geese and turkeys,
and sporadically chickens and wild birds (Brogden, 1989; Hinz et al., 1998b). This pathogen has been classified in the genera Moraxella and Pasteurella but was considered species incertae sedis in Bergey’s Manual of Systematic Bacteriology (Bøvre, 1984; Mannheim, 1984). Its affiliation with the Flavobacterium-Cytophaga lineage was suggested by the presence of menaquinones as sole respiratory quinones and of branched-chain fatty acids in high percentages, the absence of carbohydrate fermentation, a similar pattern of hydrolytic enzymes, the low DNA base ratio, and the lack of flagellation (Piechulla et al., 1986; Rossau et al., 1991). In 1993, DNA-rDNA hybridization experiments unequivocally demonstrated that this bacterium indeed belonged to the Flavobacterium-Cytophaga lineage (Segers et al., 1993). A novel genus, Riemerella, was proposed to accommodate this bacterium because of its genomic divergence from allied taxa and because of its unique chemotaxonomic and phenotypic properties, which included a capnophilic metabolism (Segers et al., 1993). Subsequent 16S rRNA gene sequence analysis confirmed these initial rRNA hybridization-based fi
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