Numerical Taxonomy Study of the Enterobacteriaceae

Abstract

Three hundred and eighty-four strains of bacteria representing the genera of the Enterobacteriaceae were examined over a wide range of biochemical, physiological, and morphological characters. The data were subjected to numerical analysis, and the resulting 33 clusters were equated as far as possible with established taxa within the Enterobacteriaceae. The clusters formed three groups. Group A corresponded to the tribe Klebsielleae and consisted of the genera Enterobacter, Klebsiella, and Serratia. The data suggest that Enterobacter and Klebsiella could be combined into a single genus, whereas Hafnia alvei should be retained in a genus separate from Enterobacter. Group B comprised the tribes Edwardsielleae, Salmonelleae, and Escherichieae. Strains of Edwardsiella species fell into two clusters, suggestive of possible biotype differences or perhaps two separate species, Many of Kauffmann's biochemical subgroup 1 salmonellae could be combined into a single species, which on grounds of priority should be designated Salmonella enteritidis (Gaertner) Castellani and Chalmers. However, there are other subgroup 1 serotypes which clearly do not belong in this species. Further study is suggested. Three species of Shigella, i.e., S. boydii. S. flexneri, and S. dysenteriae, were not separated by the analyses performed in this study. Either the three species cannot be identified on the basis of the biochemical characters employed or their identification requires considerable modification. Also included in group B were members of the genus Yersinia. Group C, representing the tribe Proteae, requires considerable revision, if a classification reflecting both molecular genetic and phenetic taxonomic relationships is to be attained.With the application of computers to the analysis of data recorded in taxonomic studies, microbial classification has, in the last 15 years, received increased attention and interest. Papers published on the application of numerical techniques to bacterial taxonomy now run into many hundreds (ll), and the majority of these have enabled considerable progress to be made in this field.One area in which the application of numerical taxonomic techniques has been lacking is in examining relationships among members of the Enterobacteriaceae. Several papers have been published in which the authors examined a wide range of bacteria, among which were included some of the enteric organisms (22,26,65). In addition, individual groups of this family have been selected for study, notably Serratia (12, 27), Erwinia (49), Salmonella (48), the tribe is, the Enterobacteriaceae appeared to be made up of a continuous spectrum of bacteria showing little evidence of generic or specific subgroupings.A larger study (4) including mainly members of the tribe Klebsielleae and reference strains of other enteric genera did show evidence of generic subgroupings. However, this study remains open to criticism because of the small number of characters recorded for each strain.One of us (R. S.) accumulated a large amount of data on the ...

The Genus Hafnia : from Soup to Nuts

“…Regarding more inhibitory selective media, from 25% to 60% of strains fail to grow on Salmonella-Shigella (SS) agar, while 75% to 100% of isolates are inhibited on brilliant green medium (68,73). Classic strains of H. alvei are lactose and sucrose negative and as such appear as nonfermenting colonies on enteric isolation media.…”

“…Hafnia grows in media containing 2% to 5% NaCl, over a pH range of 4.9 to 8.25, and over thermal gradients of 4°C to 44°C (56); the optimum temperature for growth has been reported as 35°C (89). Some investigations have found growth at 44°C to be variable (73). There is general agreement that almost 100% of Hafnia strains grow on MacConkey, Hektoen enteric, eosinmethylene blue, and xylose-lysine-deoxycholate agars, all of which are differential to moderately selective media (56,123,124).…”

Hybridization of Deoxyribonucleotide Sequences of Yersinia enterocolitica and Other Selected Members of Enterobacteriaceae

“…In a similar comparison with other members of Enterobacteriaceae, Y . enterocolitica was also resolved in an independent group (11).…”

Molecular and Phenotypic Characterization of Potentially New Shigella dysenteriae Serotype

“…Shigellae are nonmotile, nonencapsulated bacilli that conform to the definitions of the family Enterobacteriaceae and the tribe Escherichiae. Several studies on nutritional characterization, numerical taxonomy, and enzyme electrophoresis (11,16,21,28,32) have justified the historical differentiation between Shigella spp. and E. coli and the recognition of four species within the genus Shigella: S. dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei, also known as groups A, B, C, and D, respectively.…”