PubMed Health⌕ Search

Biomedical subjects

W R Willcox

Publications and source records attributed to W R Willcox.

9 recordsLinked to original sources
PubMed1978

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.

Bacteriological Techniques↗
PubMed1977

A comparison of typing methods for Serratia marcescens.

A simple method for the bacteriocine typing of Serratia marcescens without the use of induction was sought. The results of a mutual inhibition experiment with 89 unrelated cultures indicated that a bacteriocine-susceptibility method would give more discrimination between strains than would a bacteriocine-production method. A cross-streaking technique for bacteriocine-susceptibility typing without previous induction was developed, and its performance was compared with that of another susceptibility-typing method in which cell-free lysates of the producer strains were obtained by induction with mitomycin C.Replicate typing of the same collection of cultures by both methods indicated that small variations in pattern were common and that larger variations occurred occasionally. Differences in pattern of less than two strong reactions in the mitomycin-C induction method, and of less than three strong reactions in the cross-streaking method, should therefore not be taken as evidence that strains can be distinguished.Sets of cultures of Ser. marcescens, 178 in total, from a number of supposed incidents of infection in hospitals, were used to evaluate the two bacteriocine-typing methods; all of the cultures were also O serogrouped. Comparison of the typing patterns of members of the same O serogroup from clear-cut incidents of infection confirmed that results of acceptable reliability could be obtained by either bacteriocine-typing method by the application of the appropriate ;difference' rule. When so interpreted, the cross-streaking method appeared to be slightly the more discriminatory.The greatest discrimination between strains was obtained by the use of a ;hierarchical' typing system in which the strains were first O serogrouped, and the cross-streaking method of bacteriocine typing was then used to make subdivisions within O serogroups.

Bacteriocins↗
PubMed1977

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.

Bacteriological Techniques↗