Summary. Twenty-seven strains of gram-negative anaerobic bacteria isolated from patients with non-gonococcal urethritis (NGU-associated strains) were compared with reference strains of Bacteroides ureolyticus and representatives of other species of Bacteroides and Fusobacterium. Conventional biochemical tests, electrophoretic (PAGE) protein profiles and DNA base compositions of 29-5+ 1-2 mol % G + C indicated striking similarities between the NGU-associated strains and B. ureolyticus. Three of the reference strains previously assigned to that species were atypical in some respects as was one of the strains from urethritis and one strain, NCTC 10939, was incorrectly classified as B. ureolyticus. Casein hydrolysis by B. ureolyticus was the principal test difference between the two sets of strains. DNA-DNA hybridisation results of 2 72% at optimum temperature conditions provided further evidence of the close relationship between B. ureolyticus and the NGU-associated strains and we conclude that these organisms should be identified as B. ureolyticus. There was insufficient evidence for recognising subspecies or biotypes within this revised concept of B. ureolyticus although several types (PAGE-type I, 17 strains; type II,6 strains; type III,3 strains) were detected which might provide the basis for future studies of hospital strains. The DNA base composition and hybridisation data indicated that B. ureolyticus was not related to other species of Bacteroides or Fusobacterium.

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The results of the identification of 933 strains of Gram-negative, aerobic, rod-shaped, fermentative bacteria ( Enterobacteriaceae, Pasteurellaceae, Vibrionaceae) by a probabilistic method, in a computer, are given. The identification rate on the matrix was 89.2%. Many of the strains were atypical and had caused difficulty in identification in medical diagnostic laboratories. The results are given for each taxon by genus and species. I N T R O D U C T I O NA computer-assisted conditional probability method for the identification of enterobacteria was first described by Dybowski & Franklin (1968) and Lapage et al. (1970) used a similar scheme to successfully identify up to 80% of 279 freshly isolated strains. Later, Bascomb et al. (1973) published a matrix for the identification of Gram-negative rods of clinical importance and discussed its use in the identification of 1079 reference strains; the general aspects of probabilistic identification and the mathematical model used were described by Lapage et al. (1973) and Willcox et al. (1973), respectively. This latter matrix was then used as the basis for an identification service in our laboratory, the methods for which were reviewed by Willcox et al. (1980). In the operation of the identification service, the test results obtained for strains submitted for identification were accumulated by computer. These results were then sorted by taxon and printed in the form of summaries, as described by Holmes & Hill (1985). From these summarized results a revised matrix was derived for the fermentative organisms and, following evaluation, this matrix is now in current use for the routine identification service.In this paper we present the results obtained in the identification of 933 strains of bacteria belonging to 110 taxa in the revised probability matrix. METHODS Overallprocedure.A matrix was constructed which gave the probability of a strain of any given taxon yielding a positive result in each of the chosen tests (Table 1). Individual strains were then identified on the basis of these results.Taxa. Of the taxa chosen for the matrix (Table I), the majority gave a fermentative result in the oxidation/fermentation (O/F test) of Hugh & Leifson (1953). A few non-fermentative taxa were also included; these were taxa that produce acid from glucose in peptone/water/sugar media and that may possess other characteristics by which they may be confused with fermentative organisms.Although the range of taxa was selected primarily to include those of known medical importance and those likely to occur in medical specimens, efforts were made to include as many recently described species as possible, so as to facilitate recognition of the latter should they occur in human clinical or veterinary material. Particular attention was paid to ensure inclusion of all Enterobacteriaceae taxa described in Bergeys Manual of Systematic Bacteriology (Brenner, 1984). The majority of the taxa are recognized species, genera or subgenera. Some are t Present address: Gibco-Sensititre, Imberhorne La...

Chromosomal DNA from 26 strains of Providencia stuartii isolated mainly in hospitals in the United Kingdom and reference strains of P. stuartii, P. rustigianii, and Proteus vulgaris were digested with the restriction endonucleases EcoRI and HindIII. After electrophoresis in agarose gels, the fragments were subjected to Southern blot hybridization analysis with a biotin-labeled cDNA probe transcribed from a mixture of 16S and 23S rRNA from P. stuartii NCTC 11800T. The pattern of bands (the rDNA fingerprint), which depended on restriction fragment length polymorphism containing rRNA genes, was used as a measure of minor genomic variation within and between species. The P. stuartii clinical isolates had similar total digest patterns, but the rDNA fingerprints revealed some heterogeneity between strains, with EcoRI digests providing better strain discrimination than HindIII. Such rDNA fingerprints comprised between five and seven bands with sizes in the range of 5 to 28 kilobases. The 11 different EcoRI patterns were compared by numerical analysis, and several groups or subgroups of strains were identified. Over half (15 of 26) of the urease-negative isolates (subgroups Aa and Ab) had patterns that differed only by the presence or absence of a 25-kilobase band. Urease-negative strains from other clinical material were more heterogeneous in their patterns. No correlation was apparent between strain pattern group and urease production or geographic location of isolate. The P. stuartii rDNA fingerprints were quite distinct from those of allied Providencia and Proteus species and provided a more sensitive measure of minor genomic differences than total DNA digests did.

A probability matrix for computer-assisted identification of vibrios has been constructed, based on the API 20E system. Data were gathered from 173 strains representing 31 taxa of vibrios and related organisms, from a variety of sources. The matrix was tested internally by four statistical programs. Program OVERMAT tested the separation and program MOSTTYP the discretion and homogeneity of the taxa. Most of the taxa were satisfactory but a few were less so; reasons for this are discussed. Program CHARSEP and program DIACHAR tested the separation and diagnostic values, respectively, of the characters used. The overall test error was 4.5%. The matrix was assessed externally by its performance in the identification of vibrio-like strains isolated from freshwater. Of 243 wild strains, 79.4% were identified with ten taxa, with a Willcox score of greater than or equal to 0.99.