Riichi Sakazaki

Two epidemics of diarrhoeal disease possibly caused by Plesiomonas shigelloides

Two epidemics of water-borne diarrhoeal disease involving a total of 1000 persons are reported. In both epidemics, none of the usual bacterial entero-pathogens were recognized and Plesiomonas shigelloides was the only suspect aetiological agent isolated. The ecology of P. shigelloides was investigated in these outbreaks. It was recognized as an inhabitant of fresh surface water and its presence was closely related to warm weather.

A survey of Plesiomonas shigelloides from aquatic environments, domestic animals, pets and humans.

We conducted a survey during the period from 1974 to 1976, to determine the distribution of Plesiomonas shigelloides in human faeces, the intestinal contents of cattle, swine, poultry, dogs, cats, fresh water fish, and river water and sludge from wet riverbeds in the vicinity of Tokyo. Isolation of the organisms was performed by using Salmonella-Shigella (SS) agar and deoxycholate-hydrogensulphide-lactose (DHL) agar plates. P. shigelloides was isolated from 3 (0.0078%) of 38454 healthy Tokyoites, 37 (3.8%) of 967 dogs, 40 (10.3%) of 389 cats, 25 (10.2%) of 246 fresh water fish, 64 (12;8%) of 497 river water samples, and 2 of 19 (10.5%) sludge samples. Of 302 strains isolated, from dogs, cats, fresh water fish, river water and healthy carriers, 196 were typed to 50 serovars. Most of the serovars were found to be similar to strains isolated from patients with gastroenteritis due to P. shigelloides.

Leclercia adecarboxylata Gen. Nov., Comb. Nov., formerly known asEscherichia adecarboxylata.

The nameLeclercia adecarboxylata is proposed for a group of the family Enterobacteriacae previously known asEscherichia adecarboxylata. Leclercia adecarboxylata can be phenotypically differentiated from all other species of Enterobacteriaceae. The members of this species are positive for motility, indole production, methyl red, growth in the presence of KCN, malonate, beta-galactosidase, beta-xylosidase, esculin hydrolysis, gas production fromd-glucose, and acid production fromd-cellobiose,d-lactose, melibiose,l-rhamnose, adonitol,d-arabitol, dulcitol, and salicin; the strains were negative for Voges-Proskauer, citrate (Simmons), H2S (Kligler), lysine and ornithine decarboxylases, arginine dihydrolase, phenylalanine deaminase, gelatinase, DNase, Tween-80 hydrolysis, and acid production from myoinositol and alpha-methyl-d-glucoside. Fermentation ofd-raffinose,d-sucrose, andd-sorbitol is variable with strains. DNA relatedness of 11 strains ofL. adecarboxylata to three strains including the type strain of this species averaged 80% in reactions at 65°C. DNA relatedness to other species in Enterobacteriaceae was 2%–32%, indicating that this species was placed in a new genusLeclercia gen. nov. The type strain ofL. adecarboxylata is ATCC 23216.

Klebsiella ornithinolytica sp. nov., formerly known as ornithine-positiveKlebsiella oxytoca

The nameKlebsiella ornithinolytica sp. nov. is proposed for a group ofKlebsiella strains referred to previously as NIH Group 12 at the National Institute of Health, Tokyo. The members of this species are Gram-negative, encapsulated, nonmotile rods with the general characteristics of the familyEnterobacteriaceae and of the genusKlebsiella. They give positive results in tests for indole production, Voges-Proskauer, citrate utilization, lysine and ornithine decarboxylases, urease, β-galactosidase, malonate utilization, growth in KCN, and esculin hydrolysis, and they produce acid and gas fromd-glucose, and acid froml-arabinose, cellobiose, lactose, melibiose, raffinose, rhamnose, sucrose, trehalose,d-xylose, adonitol,d-arabitol, myo-inositol, sorbitol, arbutin, salicin, α-methyl-d-glucoside, and mucate. They give negative drolysis, DNase, pectinase, and acid production fromd-arabinose, melezitose, and dulcitol. They can grow at 4°C and 42°C, and do not produce any pigment. DNA relatedness of eight strains ofKlebsiella ornithinolytica to three strains including the type strain of this species averaged 88% in reaction at 75°C. DNA relatedness to the already recognizedKlebsiella species inEnterobacteriaceae was 1 to 20%. Phenotypic and DNA relatedness data also indicated that a group of organisms referred to as Enteric Group 47 orKlebsiella Group 47 at the Centers for Disease Control (Atlanta, Georgia) was identical withK. ornithinolytica. The type strain ofK. ornithinolytica is NIH 90-72 (JCM 6096).

Two community outbreaks of human infection with Yersinia enterocolitica.

Two outbreaks of human infection with Yersinia enterocolitica in Shizuoka, Japan are described. This is the first report of community outbreaks of infection with this organism in Japan, and possibly in the world. All the strains isolated in each outbreak belonged to O antigen group 3, biotype 4, of the species. Despite much effort, the source and mode of spread of the infection were not established.

Transfer ofHaemophilus equigenitalis Taylor et al. 1978 to the genusTaylorella gen. nov. asTaylorella equigenitalis comb. nov.

The taxonomic position ofHaemophilus equigenitalis Taylor et al. 1978, the causative agent of contagious equine metritis, was studied in comparison with phenotypically similar organisms such asMoraxella, Legionella, and others.Haemophilus equigenitalis is a microaerophilic, Gram-negative, nonmotile, short rod; the mean base composition of deoxyribonucleic acid of this organism is 36.5±0.5 mol% G+C. It shows best growth on chocolate agar, but very poor or no growth on plain nutrient agar and blood agar, although it requires no X- or V-factors for the growth. It is positive in catalase, oxidase, phosphatase, and phosphoamidase tests, but very unreactive in other biochemical tests for routine use. It produces no acid from any carbohydrates nor glycosidase. Arylamidase activities of the organism to β-naphtylamide derivatives of various amino acids, and di- and tripeptides were also compared with those of other taxa. The group of this organism was different from other known taxa in the numerical analysis of its phenotypic characteristics, DNA base composition, and DNA-DNA hybridization. These data indicate thatH. equigenitalis does not belong in the genusHaemophilus nor other known genera, but rather in a new genus. Therefore, we propose thatHaemophilus equigenitalis be reclassified in a new genusTaylorella asTaylorella equigenitalis.

Numerical Taxonomy Study of the Enterobacteriaceae

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 Kauffmanns 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.

Taxonomy of Some Recently Described Species in the Family Enterobacteriaceae

The taxonomic positions of several recently described species, Levinea malonatica, Levinea amalonatica, Citrobacter diversus, and Enterobacter agglomerans, were investigated by numerical analysis. A set of 141 strains, for which a total of 240 characters was recorded, was analyzed and also compared with representatives of a set of 384 strains of bacteria, examined in an earlier study, representing genera within the family Enterobacteriaceae. Three clusters of Citrobacter spp. were observed, Citrobacter freundii, Citrobacter spp., and Levinea amalonatica, with strains received as Citrobacter diversus and Levinea malonatica clustering with the Citrobacter spp. Citrobacter intermedius was concluded to be synonymous with C. freundii. L. malonatica, from the results of this study, was included in the species C. diversus. Hydrogen sulfide-positive strains of Escherichia coli were not judged to warrant separate species status. Klebsiella aerogenes, Klebsiella pneumoniae, Klebsiella oxytoca, and Klebsiella edwardsii were found to be highly related (similarity values > 90%). It is proposed that these species be merged into a single species, Klebsiella pneumoniae.

Two new Escherichia coli O groups: O172 from »Shiga‐like» toxin II‐producing strains (EHEC) and O173 from enteroinvasive E. coli (EIEC)

Two Escherichia coli strains were established as antigenic test strains for two new O groups, O172 and O173. The O172 strain (EHEC) which produces »Shiga‐like« toxin II (verocytotoxin 2) was isolated from a case of haemorrhagic colitis while the enteroinvasive O173 strain (EIEC) originated from a child with diarrhoea.

Re‐Speciation of the Original Reference Strains of Serovars in the Citrobacter freundii (Bethesda‐Ballerup Group) Antigenic Scheme of West and Edwards

The antigenic scheme for the Bethesda‐Ballerup group of bacteria established by West and Edwards in 1954 has continued to be applied as a serotyping scheme for Citrobacter freundii. In 1993, however, the classification of the Citrobacter was drastically revised and the species C. freundii redefined by Brenner et al. Accordingly, to judge the propriety to continuously use a single antigenic scheme for the C. freundii complex, the 90 reference strains listed in the antigenic scheme for C. freundii by West and Edwards were characterized phenotypically and specified based on the revised classification. Of these 90 strains, two strains of Hafnia alvei and one of Escherichia coli were found. Among the remaining 87 reference strains, Citrobacter youngae was the predominant species (40 strains), followed by Citrobacter braakii (25 strains), Citrobacter werkmanii (13 strains), and the unnamed Citrobacter genospecies 10 of Brenner et al (six strains). Citrobacter freundii, as redefined, accounted for only three strains and ranked behind the other four species. No overlapping with most of the 42 O‐groups and 82 H‐antigens was recognized between species with few exceptions. O‐groups 1–9 inclusive, which were estimated to represent more than 90% of the former C. freundii strains, occurred in strains of C. youngae and C. braakii; and all nine strains of O‐group 29, formerly known as the Ballerup group, were identified as C. braakii. These findings suggest that further study of the serotyping system is needed for all H2S‐producing Citrobacter species.