A taxonomic study of clinical isolates of Pseudomonas pickettii, 'P. thomasii' and 'group IVd' bacteria.

On the basis of cluster analysis, average similarities within and between groups, and DNA base composition of selected strains, Pseudomonas pickettii appeared to be a distinct species comprising several biotypes. Although some or all of these biotypes, represented by subclusters in our computer study, may ultimately warrant recognition as separate species, our results were not conclusive enough to warrant such a proposal at present. Most strains tentatively named 'P. thomasii' could be included in P. pickettii so that the name P. pickettii, which was validly published whilst 'P. thomasii' was not, takes priority over 'P. thomasii'. Strains of Group Va (Tatum et al., 1974) examined were also included in P. pickettii. Group IVd (King, 1964) did not appear to be a natural group but some of the strains could also be included in P. pickettii.

Identification of Gram-negative non-fermenters and oxidase-positive fermenters by the Oxi/Ferm tube.

Since the recent introduction of the Roche Oxi/Ferm Tube to the UK two identification schemes have been developed by the manufacturer for use with the kit. We evaluated the success of these two schemes in identifying 222 predominantly culture collection strains belonging to 45 taxa of non-fermenters and nine taxa of oxidase-positive fermenters. The strains were chosen to represent all the taxa included in the two identification schemes developed by the manufacturer and we have therefore been able to assess the overall success of identification by the two schemes. Since, however, our choice of strains does not reflect their incidence in clinical material, our identification rates are not necessarily those that might be obtained in a routine clinical laboratory. The most advanced identification scheme so far developed for the Oxi/Ferm Tube (CCIS System 1977-1432) allowed 62% of the 222 strains to be correctly identified although a disturbing feature was that more of the strains that were not correctly identified were incorrectly identified (24%) rather than not identified (14%); these figures represent an improvement over the earlier identification scheme (CCIS System 1976-621-74346) for which the corresponding figures were 56%, 32%, and 12%. CCIS System 1977-1432 seems likely to give a better performance in a routine clinical laboratory than in this study since for those taxa which, we would judge from the material sent to us for identification, are most commonly seen in a routine laboratory (Acinetobacter calcoaceticus, A. lwoffii, Pseudomonas aeruginosa, P. fluorescens, P. maltophilia, P. pseudoalcaligenes, and P. putida) 89% were correctly identified, none remained unidentified, and 11% were incorrectly identified. Thirty strains, each of a different taxon, were tested in triplicate to assess the reproducibility of reactions in the Oxi/Ferm Tube.

Flavobacterium odoratum: a species resistant to a wide range of antimicrobial agents.

During the period 1966-77, 24 strains of Flavobacterium odoratum were identified from among strains of Gram-negative, non-fermentative bacteria submitted to the National Collection of Type Cultures for computer-assisted identification. The F. odoratum strains showed resistance to therapeutic levels of gentamicin, tobramycin, amikacin, and carbenicillin as well as to several other antimicrobial agents generally useful in the treatment of infections caused by Gram-negative, non-fermentative bacteria. Two strains isolated from amputation stumps and another three strains isolated in significant numbers from urine specimens were possibly opportunist pathogens. The biochemical characteristics of the 24 strains, the proposed neotype strain of F. odoratum, and three strains representative of a group, referred to at the Center for Disease Control, Atlanta as group M-4f, were compared with those of biochemically similar species which may be isolated from clinical material.

Distribution in clinical material and identification of Pseudomonas maltophilia.

During the 10-year period ending March 1976, 128 (8.5%) of 1506 strains of Gram-negative non-fermentative bacteria submitted to the National Collection of Type Cultures for computer-assisted identification have been strains of Pseudomonas maltophilia. These figures suggest that Ps. maltophilia is both a relatively common species in clinical material in the United Kingdom and also that many laboratories experience difficulty in identifying this species. We report the sources from which our strains were isolated and also characteristics of the species by which it may be recognised. The clinical significance of Ps maltophilia is discussed and also the susceptibility of this species to certain antimicrobial agents.

The causative organism of contagious equine metritis 1977: proposal for a new species to be known as Haemophilus equigenitalis.

The aetiological agent of contagious equine metritis (CEM) has been investigated bacteriologically in a wide range of cultural and conventional biochemical tests, in the eletron microscope, for DNA base composition (36.1 per cent GC), for susceptibility to various antimicrobial agents and antigenically by means of tube and slide agglutination tests. The organism is a fastidious, Gramnegative, non acid-fast coccobacillus which in biochemical tests is very unreactive. In conventional tests, only the oxidase, catalase and phosphatase tests were positive. Dependance on neither X nor V factors could be demonstrated, but some stimulation of growth by X factor was observed. The organism could not be identified with any known species and even allocation to an appropriate characters, we propose the organism as a new species of the genus Haemophilus: H. equigenitalis, type strain NCTC 11184 (61717/77).

Identification of Enterobacteriaceae by the API 20E system.

Since the introduction of the API 20E kit a number of identification schemes have been developed by the manufacturer for use with the kit. We evaluated the success of these various schemes in identifying 206 strains belonging to 34 taxa of the family Enterobacteriaceae. Many of the strains were atypical and only 94% could be identified by our own system of 50 conventional tests and a computer program. The most advanced identification scheme so far developed for the API 20E kit (the Analytical Profile Index and complementary Computer Service) allowed 88% of the 206 strains to be correctly identified, although 2% were incorrectly identified. The tests in the API 20E kit and 52 conventional tests were separately evaluated for their ability to discriminate between the 34 taxa considered in this study. Our results suggest that replacing some of the tests in the present API 20E kit might further improve its diagnostic performance.

Base composition, size and sequence similarities of genoma deoxyribonucleic acids from clinical isolates of Pseudomonas putrefaciens.

The mean base compositions of DNA from 27 strains of Pseudomonas putrefaciens, P. rubescens and P. piscicida ranged from 43-4 to 53-2 mol% GC with genome sizes from 3.04 X 10(9) to 4.23 X 10(9) daltons. On the basis of in vitro DNA-DNA binding, estimated spectrophotometrically from initial renaturation rates, P. putrefaciens strains were heterogenous in the extent to which they shared similar nucleotide sequences, and were divided into four DNA homology groups. The DNA characteristics of strains in these groups correlated with several biochemical characteristics that facilitated identification of clinical isolates of P. putrefaciens. The two species P. putrefaciens and P. rubescens appear to be synonymous and none of the four groups of P. putrefaciens was related in DNA sequences to P. pisicida. Pseudomonas putrefaciens should theretofore be retained as a single species and characteristics for identifying the various groups within the species are listed.

Strains of Achromobacter xylosoxidans from clinical material.

Eleven strains of Achromobacter xylosoxidans have been received from among 1106 strains of Gram-negative, non-fermentative bacteria submitted to the National Collection of Type Cultures for computer-assisted identification since 1 January 1972. The strains showed resistance to a wide range of antimicrobial agents and five of the isolates possibly played a pathogenic role. The biochemical characteristics of these 11 strains were compared with those of three culture collection strains.

Test reproducibility of the API (20E), Enterotube, and Pathotec systems.

Thirty-three strains of bacteria (30 Enterobacteriaceae and one strain each of Aeromonas formicans, A. hydrophila, and Plesiomonas shigelloides) were tested three times in each of 27 conventional tests and in the API, Enterotube, and Pathotec systems. The results obtained were analysed for test reproducibility within each kit, correlation of the kit tests with the equivalent conventional media, and the identification of the strains by the kits. Difficulties in evaluation and comparison of identifications are discussed. A practical evaluation of the kits was also made.

Strains of Pseudomonas putrefaciens from clinical material.

Eight strains of Pseudomonas putrefaciens have been received from among 466 strains of Pseudomonas submitted to the Computer Trials Laboratory for identification over the last eight years. Two of the strains of P. putrefaciens from patients with otitis media and otitis externa respectively appear to have played a pathogenic role. The biochemical characteristics of these eight strains were compared with those of seven culture collection strains.

Sensitivity of Citrobacter freundii and Citrobacter koseri to cephalosporins and penicillins.

An examination of 99 field and reference strains of Citrobacter freundii showed 79% of them to be resistant to cephaloridine and sensitive to carbenicillin, while 96% of 45 field and reference strains of Citrobacter koseri examined were sensitive to cephaloridine and resistant to carbenicillin. Susceptibility tests with these two antibiotics are therefore useful in separating the two species of Citrobacter.

The ortho-nitrophenol (ONPG) test and acid from lactose in Gram-negative genera.

The results are given of the ortho-nitrophenol test for beta-galactosidase production (ONPG test) on 588 strains of 123 aerobic species of bacteria, representing 30 genera. Apart from some strains of Erwinia herbicola (synonym Chromobacterium typhiflavum) and of Yersinia spp, these strains were not members of the Enterobacteriaceae, in which family the ONPG test is widely used and well documented. The strains were also tested for acid production from 1, 5, and 10% lactose and the findings are discussed in relation to the ONPG test.

Flavobacterium meningosepticum from cases of meningitis in Botswana and England.

Two strains of Flavobacterium meningosepticum isolated from cases of meningitis are described. One was isolated in Botswana from a man with an aplastic anaemia, the other in the UK from an infant who was probably infected in Bangladesh. The severity of the infection, the characterization of the organism, and the possibility that infection may be found in the UK are discussed.