Suppression of soilborne disease by fluorescent pseudomonads may be inconsistent. Inefficient root colonization by the introduced bacteria is often responsible for this inconsistency. To better understand the bacterial traits involved in root colonization, the effect of two plant species, flax (Linum usitatissinum L.) and tomato (Lycopersicon esculentum Mill.), on the diversity of soilborne populations was assessed. Fluorescent pseudomonads were isolated from an uncultivated soil and from rhizosphere, rhizoplane, and root tissue of flax and tomato cultivated in the same soil. Species and biovars were identified by classical biochemical and physiological tests. The ability of bacterial isolates to assimilate 147 different organic compounds and to show three different enzyme activities was assessed to determine their intraspecific phenotypic diversity. Numerical analysis of these characteristics allowed the clustering of isolates showing a high level (87.8%) of similarity. On the whole, the populations isolated from soil were different from those isolated from plants with respect to their phenotypic characteristics. The difference in bacteria isolated from uncultivated soil and from root tissue of flax was particularly marked. The intensity of plant selection was more strongly expressed with flax than with tomato plants. The selection was, at least partly, plant specific. The use of 10 different substrates allowed us to discriminate between flax and tomato isolates. Pseudomonas fluorescens biovars II, III, and V and Pseudomonas putida biovar A and intermediate type were well distributed among the isolates from soil, rhizosphere, and rhizoplane. Most isolates from root tissue of flax and tomato belonged to P. putida bv. A and to P. fluorescens bv. II, respectively. Phenotypic characterization of bacterial isolates was well correlated with genotypic characterization based on repetitive extragenic palindromic PCR fingerprinting.

API 20E, API ZYM and eight other enzymic API systems were tested on 123 strains belonging to 18 Erwinia species, six Enterobacter agglomerans strains and 22 reference strains belonging to other phytopathogenic genera and other enterobacterial species. The data obtained, from a total of 130 tests, were subjected to numerical analysis. Test reproducibility within the API 20E system varied from 88 to 100%. The numerical analysis revealed 12 phenons; in six of these phenons two or three subphenons could be differentiated. Several of these (sub)phenons corresponded to established Erwinia species and could be differentiated from each other by 25 characters. No clearcut distinction could be made between the 'amylovora', 'carotovora' and 'herbicola' groups. Seven phenons were further analysed with the API SOCHE system. The results provided evidence for the retention of Er. quercina, Er. nigrifwns, Er. salicis, Er. amylovora, Er. rubrifaciens, Er. mallotiuora, Er. stewartii, Er. cypripedii and Er. chrysanthemi as separate taxa and supported the synonymy within the pairs Er. ananas and Er. uredovora, Er. dissolvens and Enterobacter cloacae, Er. carotovora subsp. atroseptica and Er. carotovora subsp. carotovora, Er. milletiae and one of the Er. herbicola clusters. The inadequacy of the present classification of several Erwinia species, such as Er. herbicola and Er. rhapontici, is highlighted. The results show that API systems are a useful and rapid alternative to conventional phenotypical testing for the classification and identification of Erwinia species.

A study was performed to evaluate a new manual miniaturized system, API Coryne (API-bioMerieux, Inc., La Balme les Grottes, France), in which conventional biochemical methods were used to identify 240 isolates of coryneform and related bacteria. A total of 40% of the isolates were excluded from the study because they could not be identified by conventional methods. Identifications of the 240 isolates obtained with API Coryne showed a 97.6% concordance with conventional methods (79% after 24 h of incubation, 21% after 48 h of incubation): 158 (65.8%) isolates were identified with no further testing, and extra testing was required for 76 (31.8%) isolates. In three (1.2%) cases, the organisms did not correspond to any key in the code book and could not be identified by the computer service of the manufacturer. Only three (1.2%) strains were misidentified. The system was shown to be reliable and rapid when compared with standard identification methods.

Summary. Pyogenic streptococci of Lancefield group C or group G from human or animal sources were examined with a view to increasing the number of diagnostic tests useful for their differentiation. Human strains of group G produced L-prolyl-L-arginine aminopeptidase but isolates of Streptococcus equisimilis (group C) did not. Tests for a-L-glutamate aminopeptidase together with fermentation of glycogen or sorbitol distinguished S. dysgalactiae from strains of S. equisimilis isolated from animals. It was confirmed that fermentation tests were helpful in the study of S. equi and S. zooepidemicus and that enzyme reactions helped distinguish between S. canis and the human strains of group G.

A study was designed to assess the impact of the VITEK 2 automated system and the Advanced Expert System (AES) on the clinical laboratory of a typical university-based hospital. A total of 259 consecutive, nonduplicate isolates of Enterobacteriaceae members, Pseudomonas aeruginosa, and Staphylococcus aureus were collected and tested by the VITEK 2 system for identification and antimicrobial susceptibility testing, and the results were analyzed by the AES. The results were also analyzed by a human expert and compared to the AES analyses. Among the 259 isolates included in this study, 245 (94.6%) were definitively identified by VITEK 2, requiring little input from laboratory staff. For 194 (74.9%) isolates, no inconsistencies between the identification of the strain and the antimicrobial susceptibility determined by VITEK 2 were detected by the AES. Thus, no input from laboratory staff was required for these strains. The AES suggested one or more corrections to results obtained with 65 strains to remove inconsistencies. The human expert thought that most of these corrections were appropriate and that some resulted from a failure of the VITEK 2 system to detect certain forms of resistance. Antimicrobial phenotypes assigned to the strains by the AES for ␤-lactams, aminoglycosides, quinolones, macrolides, tetracyclines, and glycopeptides were similar to those assigned by the human expert for 95.7 to 100% of strains. These results indicate that the VITEK 2 system and AES can provide accurate information in tests for most of the clinical isolates examined and remove the need for human analysis of results for many. Certain problems were identified in the study that should be remediable with further work on the software supporting the AES.The VITEK 2 system is a new system that automatically performs rapid identification and antimicrobial susceptibility testing on a manually prepared inoculum (1). The Advanced Expert System (AES) is designed to analyze results generated by the VITEK 2 system for biologic validity and then provide comments on the results. One important function of the AES is to look for inconsistencies between the identification of the organism and the antimicrobial susceptibility of the isolate. Another important function is to ascertain the antimicrobial phenotype of the isolate based on results of susceptibility tests. A third function is to deduce the susceptibility of the organism to drugs not tested based on its susceptibility to the antibiotics actually tested.In a previous study, the ability of the AES to correctly ascertain the ␤-lactam phenotype of isolates of Enterobacteriaceae and Pseudomonas aeruginosa was determined using a panel of 196 strains collected worldwide which had been characterized by biochemical and molecular techniques for their ␤-lactamase content (6). The results of that study showed that the AES correctly identified the ␤-lactam phenotype of 183 (93.4%) of these isolates despite the inclusion of many rare phenotypes in the isolate panel. The study, however, did not assess the...