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 ofEnterobacteriaceae 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),

We characterized 13 cultures of the enteric bacterium causing enteric septicemia of catfish by studying their biochemical reactions, deoxyribonucleic hybridizations, and deoxyribonucleic acid guanine-plus-cytosine contents. We confirmed that this bacterium is a new species, which is most closely related to Edwardsiella tarda of the family Enterobacteriaceae. Five strains of the bacterium causing enteric septicemia of catfish were 80% or more related to the type strain, SECFDL GA 77-52 (= CDC 1976-78 = ATCC 33202), in 60°C deoxyribonucleic acid homology reactions. Species level relatedness among the 13 strains which we studied was demonstrated by the more than 80% relatedness in 75°C reactions. The bacterium causing enteric septicemia of catfish was most closely related to E. tarda (56 to 62%) in 60°C reactions. The guanine-plus-cytosine was 53 mol%, as determined by buoyant density centrifugation. We propose the name Edwardsiella ictaluri sp. nov. for the bacterium causing enteric septicemia of catfish.Enteric septicemia of catfish (ESC) is a newly described bacterial disease primarily of cultured channel catfish (Ictalurus punctatus) (9). The causative agent of this disease is a gram-negative, rod-shaped, 0.5-by 1.25-pm, oxidase-negative, peritrichous, fermentative bacterium that has been isolated 26 different times from the kidney tissues of moribund catfish. Biochemically, this organism is most similar to Edwardsiella tarda but differs from E. tarda in several key diagnostic characteristics (1).ESC was fist detected in 1976. Although not always consistent, the clinical signs of this disease in I. punctatus are typical of the acute bacterial septicemias caused by E. tarda, Aeromonas hydrophila, and Pseudomonas fluorescens ( 5 , 11).ESC presently constitutes an economic threat to catfish farmers in Alabama, Georgia, and Mississippi. The pathogenicity of the ESC bacterium to species of fish other than catfish has not been demonstrated, although it has been isolated from channel catfish (I. punctatus), white catfish (Ictalurus catus), and brown bullhead (Ictalurus nebulosus). In this paper we characterize, classify, and name the ESC bacterium.

The name Escherichia v'ulneris sp. nov. (formerly called Alma group 1 and Enteric group 1 by the Centers for Disease Control and API group 2 by Analytab Products, Inc.) is proposed for a group of isolates from the United States and Canada, 74% of which were from human wounds. E. v'uilneris is a gram-negative, oxidase-negative, fermentative, motile rod with the characteristics of the family Enterobacteriaceae. Biochemical reactions characteristic of 61 E. illtneris strains were positive tests for methyl red, malonate, and lysine decarboxylase; a delayed positive test for arginine dihydrolase; acid production from D-mannitol, Larabinose, raffinose, L-rhamnose, D-xylose, trehalose, cellobiose, and melibiose; negative tests for Voges-Proskauer, indole, urea, H,S, citrate, ornithine decarboxylase, phenylalanine deaminase, and DNase; and no acid from dulcitol, adonitol, myo-inositol, and D-sorbitol. Two-thirds of the strains produced yellow pigment. Most strains gave negative or delayed positive reactions in tests for lactose, sucrose, and KCN. The E. vulneris strains tested were resistant to

T h e a u t h o r s g i v e a f u l l d e s c r i p t i o n o f a n e w s p e c i e s a n d g e n u s t o b e i n c l u d e d i n t h e f a m i l y E n t e r o b a c t e r i a c e a e . T h e g e n e r i c n a m e E d w a r d s i e l l a ( E w i n g a n d M c W h o r t e r ) a n d t h e s p e c i e s n a m e E d w a r d s i e l l a t a r d a a r e s u g g e s t e d f o r u s e i n c o n n e c t i o n w i t h t h e b a ct e r i a d e s c r i b e d .The purpose of this paper is to provide a description of the biochemical reactions given by a group of cultures that have been collected and studied in these laboratories since e a r l y i n 1959, and to r e p o r t the r e s u l t s of p r e l i m i n a r y s e r ological investigations.A s e a r c h of the literature did not reveal a description of a microorganism that closely r esembled m e m b e r s of the new group, which i s r e f e r r e d to simply as "bacterium 1483-59,"The word "new" i s not used without reservation, since it seemed probable that the bacteria have been isolated in the past. F u r t h e r , we a r e informed by D r , R. Sakazaki, of the National Institute of Health, Tokyo, (personal communication, 1964) that he p r esented a paper entitled "The New Group of Enterobacteriaceae, the Asakusa Group" a t the 1962 meeting of the Japan Bacteriological Society and that a s u m m a r y of the presentation (Japanese text) was published (Sakazaki, 1962). Dr.Sakazaki v e r y kindly furnished the authors with a t r a n s lation of the above-mentioned a b s t r a c t . F r o m this it appeared that the majority of the cultures w e r e isolated f r o m snakes and that the s t r a i n s described were s i m i l a r to those reported herein, although t h e r e were a few differences in the biochemical reactions obtained (v. id.). Also King and Adler (1964)described the isolation of a culture of bacterium 1483-59, which they labe led the "Bartho Lomew group." Their

Variation in the chromosomal genomes of newport) in isolates of clones belonging to several evolutionary lineages, some of which are distantly related, suggests that the horizontal transfer and recombination of chromosomal genes mediating expression of cell-surface antigens has been a significant process in the evolution of the salmonellae. Two divergent clone clusters of S. derby differ in the relative frequency with which they cause disease in birds versus mammals, and two major lineages of S. newport differ in the frequency with which their clones are associated with disease in humans versus animals.

The demonstration by multilocus enzyme electrophoresis (MLEE) that the same polysaccharide and flagellin serotypes may occur in distantly related strains suggested that horizontal transfer and recombination events involving the fliC, flEB, and rib genes are relatively frequent (3-6). ForfliC, this hypothesis subsequently was supported by partial sequencing of the gene in strains of several serovars (7) and identification of a plasmid-bornefliC-like gene (8). But the recombmiation events could not be classified as intragenic or assortative (entire gene) (9), and the generality of these findings is unknown.We here report the results of a comparative sequence analysis offliC in strains of 15 S. enterica serovars for which overall genomic relatedness has been estimated by MLEE. § Our findings demonstrate that recombination is a major evolutionary mechanism generating both allelic variation at the fliC locus and serovar diversity in natural populations.

Enterobacter asburiae sp. nov. is a new species that was formerly referred to as Enteric Group 17 and that consists of 71 strains, 70 of which were isolated from humans. Enterobacter asburiae sp. nov. strains gave positive reactions in tests for methyl red, citrate utilization (Simmons and Christensen's), urea hydrolysis, L-ornithine decarboxylase, growth in KCN, acid and gas production from D-glucose, and acid production from L-arabinose, cellobiose, glycerol (negative in 1 to 2 days, positive in 3 to 7 days), lactose, D-mannitol, a-methyl-D-glucoside, salicin, D-sorbitol, sucrose, trehalose, and D-xylose. They gave negative reactions in the Voges-Proskauer test and in tests for indole, H2S production, phenylalanine, L-lysine decarboxylase, motility, gelatin, utilization of malonate, lipase, DNase, tyrosine clearing, acid production from adonitol, D-arabitol, dulcitol, erythritol, i(myo)-inositol, melibiose, and L-rhamnose. They gave variable reactions in tests for L-arginine dihydrolase (25% positive after 2 days) and acid production from raffinose (69% positive after 2 days). Thirty-four Enterobacter asburiae sp. nov. strains were tested for DNA relatedness by the hydroxyapatite method with 32P04-labeled DNA from the designated type strain (1497-78, ATCC 35953). The strains were 69 to 100% related in 60°C reactions and 63 to 100% related in 75°C reactions. Divergence within related sequences was 0 to 2.5%. Relatedness of Enterobacter asburiae sp. nov. to 84 strains of members of the Enterobacteriaceae was 5 to 63%, with closest relatedness to strains of Enterobacter cloacae, Erwinia dissolvens, Enterobacter taylorae, Enterobacter agglomerans, Erwinia nimipressuralis, and Enterobacter gergoviae. All strains tested were susceptible to gentamicin and sulfadiazine, and most were susceptible to chloramphenicol, colistin, kanamycin, nalidixic acid, carbenicillin, and streptomycin. All strains were resistant to ampicillin, cephalothin, and penicillin, and most were resistant or moderately resistant to tetracycline. Enterobacter asburiae sp. nov. strains were isolated from a variety of human sources, most prevalent of which were urine (16 strains), respiratory sources (15 strains), stools (12 strains), wounds (11 strains), and blood (7 strains). The clinical significance of Enterobacter asburiae is not known. As a result of this and previous studies, proposals are made to transfer Erwinia dissolvens and Erwinia nimipressuralis to the genus Enterobacter as Enterobacter dissolvens comb. nov. and Enterobacter nimipressuralis comb. nov., respectively. * Corresponding author. dissolvens and Enterobacter nimipressuralis, respectively. These new combinations are used in the remainder of this paper. MATERIALS AND METHODS Bacterial strains. There are 71 Enterobacter asburiae sp. nov. strains in the CDC collection (Table 1). Ail strains were

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....