Atypical biogroups of Escherichia coli found in clinical specimens and description of Escherichia hermannii sp. nov

Abstract

DNA relatedness was used to define the biochemical boundaries of Escherichia coli. A large number of biochemically atypical strains were shown to belong to biogroups of E. coli. These included strains negative in reactions for indole, all three decarboxylases, D-mannitol, lactose, or methyl red and strains positive in reactions for H2S, urea, citrate, KCN, adonitol, myo-inositol, or phenylalanine deaminase. Frequency and source data are presented for these atypical E. coli biogroups. One group of KCN-positive, cellobiose-positive, yellow-pigmented strains was 84 to 91% interrelated but only 35 to 45% related to E. coli. The name Escherichia hermannii sp. nov. is proposed for this group of organisms that was formerly called Enteric Group 11 by the Enteric Section, Centers for Disease Control, Atlanta, Ga. Twenty-nine strains of E. hermannii have been isolated in the United States from a variety of clinical sources, principally wounds, sputum, and stools. Three additional strains were isolated from food. E. hermannii strains are gram-negative, oxidase-negative, fermentative, motile rods. In addition to yellow pigment and positive KCN and cellobiose tests, the biochemical reactions characteristic of 32 strains of E. hermannii were as follows: gas from D-glucose, acid from D-glucose, maltose, D-xylose, L-arabinose, L-rhamnose, and D-mannitol; no acid from adonitol or inositol; variable acid production from lactose and sucrose; positive tests for indole, methyl red, and mucate; negative tests for Voges-Proskauer, Simmons citrate, H2S, urea, phenylalanine deaminase, and gelatin hydrolysis; negative or delayed test for L-lysine decarboxylase and negative test for L-arginine dihydrolase; and positive test for ornithine decarboxylase. E. hermannii strains were resistant to penicillin, ampicillin, and carbenicillin and sensitive to other commonly used antibiotics. Wounds account for almost 50% of human isolates of E. hermannii, followed by sputum or lung isolates (ca. 25%) and stool isolates (20%). Escherichia coli was among the first species to be defined and separated from other species on the basis of DNA relatedness (2, 3, 5, 6). The strains were studied by intraspecies DNA relatedness, genome size, and guanine-plus-cytosine (G+C) content. They were chosen on the bases of geographic origin, source (animal, human, environment), site of isolation (intestinal, extraintestinal), pathogenicity, and serology. With one exception, the Alkalescens-Dispar biogroup (anaerogenic, lactose-negative, nonmotile strains), biochemical profiles, and specific atypical reactions were not considered in choosing the strains used in these studies. During the past decade several E. coli-like biogroups have been identified. Some, such as H2S-positive (10, 14, 15), urea-positive (16, 18, 21, 22), and citrate-positive (19, 23) biogroups, are assumed to be E. coli. Other less familiar biogroups include strains positive in reactions for KCN, adonitol, inositol, or phenylalanine deaminase and strains negative in reactions for methyl red or mannitol....

Phylogenetics of family Enterobacteriaceae and proposal to reclassify Escherichia hermannii and Salmonella subterranea as Atlantibacter hermannii and Atlantibacter subterranea gen. nov., comb. nov.

“…The type species is Atlantibacter hermannii. The description of this taxon is the same as that given by Brenner et al (23).…”

Serological cross-reactions between Escherichia coli O157 and other species of the genus Escherichia

“…Organisms were grown on veal infusion agar at 37°C for 18 h, suspended in sterile formalinized (0.6% [vol/vol]) physiological saline, and heated in a boiling water bath for 2 h. Suspensions were cooled and diluted with formalinized saline to a density equivalent to that of a no. 3 McFarland barium sulfate standard. Serial dilutions of 1:20 to 1:1,280 were prepared in formalinized (0.6% [vol/vol]) physiological saline (0.5 ml in round-bottom glass tubes) and mixed with an equal volume of bacterial suspension.…”

Biofilm-like structures and pathogenicity ofEscherichia hermanniiYS-11, a clinical isolate from a persistent apical periodontitis lesion

“…Escherichia hermannii was formerly classified as enteric group 11 of Escherichia coli, and reclassified as a distinct species in 1982 within the Escherichia genus on the basis of DNA-DNA relatedness (Brenner et al, 1982). Escherichia hermannii is distinguished from E. coli by its production of a yellow pigment and by various biochemical characteristics including the fermentation of cellobiose and a positive reaction to KCN (Brenner et al, 1982).…”