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The genus name Morganella was established within the family Enterobacteriaceae in 1978. Morganella morganii is the only species described thus far within this genus, and the name M. morganii has been accepted by usage in the scientific community for strains previously known as Proteus morganii. M. morganii isolates differ in their abilities to ferment trehalose and exhibit variable lysine and ornithine decarboxylase patterns, emphasizing the phenotypic heterogeneity within this species. Previous genetic studies failed to reveal separate entities within the genus Morganella. We observed some trehalose-fermenting strains with different lysine and ornithine decarboxylase patterns. Two strains were lysine and ornithine positive, 3 were lysine positive and ornithine negative, and 29 were lysine negative and ornithine positive. These strains and 25 non-trehalose-fermenting strains with different lysine and ornithine decarboxylase patterns were investigated. DNA-DNA hybridization studies and phenotypic characterizations revealed that M. morganii can be separated into three DNA relatedness groups and seven biogroups. Strains from DNA relatedness group 1 were trehalose negative, and strains from DNA relatedness groups 2 and 3 were trehalose positive. One biogroup from DNA relatedness group 2 was phenotypically indistinguishable from DNA relatedness group 3. On the basis of these studies, we propose that M. morganii be subdivided into M. morganii subsp. morganii (type strain ATCC 25830) containing biogroups A, B, C, and D (DNA relatedness group 1) and M. morganii subsp. sibonii (type strain 8103-85; = ATCC 49948) containing biogroups E, F, and G (DNA relatedness groups 2 and 3).

Escherichia fergusonii (formerly known as Enteric Group 10) and Enterobacter taylorae (formerly known as Enteric Group 19) are proposed as new species in the family Enterobacteriaceae. By DNA hybridization (32P, 60 degrees C, hydroxyapatite), strains of E. fergusonii were 90 to 97% related to the type strain (holotype) ATCC 35469. They were most closely related to Escherichia coli and more distantly related to species in other genera. E. fergusonii strains are positive for indole production, methyl red, lysine decarboxylase, ornithine decarboxylase, and motility. They ferment D-glucose with gas production and also ferment adonitol, L-arabinose, L-rhamnose, maltose, D-xylose, trehalose, cellobiose, and D-arabitol. They are negative for Voges-Proskauer, citrate utilization (17% positive), urea hydrolysis, phenylalanine deamination, arginine dihydrolase, growth in KCN, and fermentation of lactose, sucrose, myo-inositol, D-sorbitol, raffinose, and alpha-methyl-D-glucoside. By DNA hybridization (32P, 60 degrees C, hydroxyapatite), strains of E. taylorae were 84 to 95% related to the type strain (holotype) ATCC 35317. Their nearest relative was E. cloacae, to which they were 61% related. Other named species were more distantly related. Strains of E. taylorae are positive for Voges-Proskauer, citrate utilization, arginine dihydrolase, ornithine decarboxylase, motility, growth in KCN medium, and malonate utilization. They ferment D-glucose with gas production and also ferment D-mannitol, L-arabinose, L-rhamnose, maltose, D-xylose, trehalose, and cellobiose. They are negative for indole production, methyl red, H2S production on triple sugar-iron agar, urea hydrolysis, phenylalanine deamination, lysine decarboxylase, gelatin hydrolysis, and fermentation of adonitol, i-inositol, D-sorbitol, and raffinose. Both new species occur in human clinical specimens. Two strains of E. fergusonii were isolated from blood. Five stains of E. taylorae were isolated from blood, and one was from spinal fluid. These blood and spinal fluid isolates suggest possible clinical significance, but this point requires further study.

Leminorella is proposed as a new genus for the group of Enterobacteriaceae formerly known as Enteric Group 57. Strains of Leminorella gave positive tests for H2S production, acid production from L-arabinose and D-xylose, and tyrosine clearing; they were negative for indole production, Voges-Proskauer, urea hydrolysis, phenylalanine deaminase, motility, gelatin liquefaction, lysine and ornithine decarboxylases, arginine dihydrolase, growth in KCN, and acid production from adonitol, D-arabitol, cellobiose, erythritol, D-galactose, myo-inositol, lactose, maltose, D-mannitol, D-mannose, melibiose, alpha-CH3-glucoside, raffinose, L-rhamnose, salicin, D-sorbitol, sucrose, and trehalose. By DNA hybridization, strains of Leminorella were only 3 to 16% related to other Enterobacteriaceae and were divided into three groups. Leminorella grimontii is proposed as the type species for the genus and strain CDC 1944-81, ATCC 33999, is designated as the type strain. There were four strains of L. grimontii from stool specimens and two from urine specimens. L. richardii is proposed as the name for the second species (type strain, CDC 0978-82, ATCC 33998). All four L. richardii strains were from stool specimens. L. grimontii can be distinguished from L. richardii because it produces gas from glucose (100%) and acid from dulcitol (83%) and is methyl red positive (100%). One strain, CDC 3346-72, was more related to L. grimontii by DNA hybridization than to L. richardii, but the lower relatedness to both of these species indicated that it may be a third species. Biochemically it could not be distinguished from L. grimontii. All Leminorella strains were resistant (no zone of inhibition) to ampicillin, carbenicillin, and cephalothin. Some of the Leminorella strains were sent to us for Salmonella serotyping, and two reacted weakly in Salmonella antisera. The clinical significance of Leminorella is unknown.

The name Moellerella wisconsensis is proposed for a group of the family Enterobacteriaceae previously called enteric group 46. The species name, wisconsensis, was coined because six of the nine strains were isolated in Wisconsin. M. wisconsensis strains were negative for indole production, Voges-Proskauer, H2S production, urea, phenylalanine deaminase, lysine and ornithine decarboxylases, arginine dihydrolase, gas production from D-glucose, acid production from trehalose, and motility; the strains were positive for methyl red, citrate (Simmons), and acid production from lactose and raffinose and resistant to colistin. DNAs from five strains of M. wisconsensis were highly related (80 to 93% in reactions assayed on hydroxyapatite at 60 degrees C and 78 to 97% at 75 degrees C) to 32P-labeled DNA of the proposed type strain (CDC 2896-78, ATCC 35017). Labeled DNA from this type strain was only 2 to 32% related (at 60 degrees C) to DNA from 49 strains of named and unnamed species of Enterobacteriaceae. Eight of nine M. wisconsensis strains were isolated from human stool samples. Clinical information on one strain was available, and it was found to be associated with a case of diarrhea. On MacConkey agar, colonies of M. wisconsensis were bright red with precipitated bile around them and thus were indistinguishable from Escherichia coli colonies. Future studies should focus on the isolation of this new organism and its relationship to human disease.

The name Koserella trabulsii is proposed for a group of Enterobacteriaceae formerly called Enteric Group 45. This group consists of 12 strains that were originally identified as atypical Hafnia alvei. K. trabulsii strains were negative for indole production, Voges-Proskauer, H2S production, urea hydrolysis, phenylalanine deaminase, and acid production from glycerol, lactose, sucrose, and D-sorbitol; they were positive for methyl red, citrate (Simmons), lysine and ornithine decarboxylases, arginine dihydrolase (negative in 1 to 2 days and positive in 3 to 7 days), and acid production from cellobiose and melibiose; and they were resistant to the Hafnia-specific bacteriophage of Guinée and Valkenburg. They were tested for DNA relatedness by the hydroxyapatite method with 32PO4-labeled DNA from the designated type strain (CDC 3349-72, ATCC 35313). The 12 strains were 87 to 99% related in 60 degrees C reactions. Relatedness of K. trabulsii to 71 DNA hybridization reference strains of representative species of Enterobacteriaceae was 4 to 37%. It was 15 to 16% related to H. alvei. All strains were susceptible to nalidixic acid, sulfadiazine, gentamicin, kanamycin, and chloramphenicol, and 83% were susceptible to nalidixic acid, sulfadiazine, gentamicin, kanamycin, and chloramphenicol, and 83% were susceptible to tetracycline. Most of the strains were resistant or intermediate to penicillin, ampicillin, carbenicillin, colistin, and cephalothin. Five of the strains were isolated from wounds, three were from the respiratory tract, and one each was from a stool, knee fluid, water, and an unknown source. The clinical significance of this organism is not known; therefore, future studies should focus on its isolation and its relationship to human disease.

In 1972 there were only 11 genera and 26 species in the family Enterobacteriaceae. Today there are 22 genera, 69 species, and 29 biogroups or Enteric Groups. This paper is a review of all of the new organisms. It has a series of differential charts to assist in identification and a large chart with the reactions of 98 different organisms for 47 tests often used in identification. A simplified version of this chart gives the most common species and tests most often used for identification. The sources of the new organisms are listed, and their role in human disease is discussed. Fourteen new groups of Enterobacteriaceae are described for the first time. These new groups are biochemically distinct from previously described species, biogroups, and Enteric Groups of Enterobacteriaceae. The new groups are Citrobacter amalonaticus biogroup 1, Klebsiella group 47 (indole positive, ornithine positive), Serratia marcescens biogroup 1, and unclassified Enteric Groups 17, 45, 57, 58, 59, 60, 63, 64, 68, and 69.