Investigation of a pseudo-outbreak of 'Pseudomonas thomasii' in a special-care baby unit by numerical analysis of SDS-PAGE protein patterns.

Forty-two cultures of pseudomonas comprising 28 clinical isolates from a pseudo-outbreak on a Special-Care Baby Unit and 14 reference strains, including 9 type strains, of various Pseudomonas species, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis for a numerical analysis which divided the strains into 9 phenons. Two of the 28 clinical isolates were identified by biochemical tests as P. pickettii and their identification was confirmed by SDS-PAGE as they fell in the same phenon as the type strain of the species. The remaining 26 isolates, which could not be identified on phenotypic tests, fell in the same phenon as three reference strains of 'P. thomasii'. The protein patterns provided the first clear evidence that P. pickettii and 'P. thomasii' were separate taxa and that the 'outbreak' was polymicrobial in origin, in line with the probable aqueous source of contamination. We conclude that high-resolution SDS-PAGE of proteins provides an effective method of identifying and differentiating pseudomonads, especially where this cannot be done adequately using conventional biochemical tests.

Numerical analysis of SDS-PAGE protein patterns of Serratia marcescens: a comparison with other typing methods.

Twenty-five cultures comprising 18 clinical isolates of Serratia marcescens from two hospitals, the type strain of S. marcescens, two reference strains of S. marinorubra, the type or a reference strain of three other Serratia species and a reference strain of undetermined species, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into eight protein types. Comparison with O-serotyping indicated that the level of discrimination by SDS-PAGE was similar. As with O-serotyping, a secondary scheme, such as phage typing, is necessary to differentiate strains of the same protein type. We conclude that high-resolution SDS-PAGE of proteins provides an effective adjunct to other methods for typing isolates of S. marcescens.

Comparison of SDS-PAGE protein patterns with other typing methods for investigating the epidemiology of 'Klebsiella aerogenes'.

Twenty-four cultures comprising 20 clinical isolates of 'Klebsiella aerogenes' from two hospitals, a reference strain of 'K. aerogenes' and the type strains of three other Klebsiella species, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into 12 protein types. Comparison with established typing methods indicated that the level of discrimination of SDS-PAGE was similar to that achieved with conventional typing methods but the strains were grouped differently. Protein typing subdivided five serotype K3 isolates that could also be distinguished by phage typing. Conversely, three strains of protein type 11 were clearly distinguishable by both serotyping and phage typing. We conclude that high-resolution SDS-PAGE of proteins provides an effective adjunct to other methods for typing isolates of 'K. aerogenes'.

Evaluation of numerical analysis of SDS-PAGE of protein patterns for typing Enterobacter cloacae.

Twenty cultures comprising 13 clinical isolates of Enterobacter cloacae from two hospitals, the type and another reference stain of E. cloacae and the type strains of four other Enterobacter sp. and of Escherichia coli, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into nine clearly defined protein types. Comparison with established typing methods indicated that the discrimination of SDS-PAGE was similar to that achieved with conventional typing methods and all strain groups recognized by combined sero/phage typing were also found by SDS-PAGE. In addition, protein typing sub-divided a group of four serotype O3 isolates that were difficult to distinguish by phage typing. We conclude that high-resolution SDS-PAGE of proteins provides an effective method of typing isolates of E. cloacae.

Electrophoretic protein typing of Campylobacter jejuni subspecies "doylei" (nitrate-negative campylobacter-like organisms) from human faeces and gastric mucosa.

Twenty-seven strains comprising 23 clinical isolates of nitrate negative campylobacters (NNC) from Australia, South Africa, the United Kingdom and the Federal Republic of Germany, a representative of the CNW (catalase negative/weak) group and reference strains of three other Campylobacter species, were characterized by one-dimensional SDS-polyacrylamide gel electrophoresis of cellular proteins. The protein patterns were highly reproducible, and were used as the basis for a numerical analysis which showed that the reference strain (NCTC 11951) of Campylobacter jejuni subspecies "doylei", and 20 NNC isolates formed a distinct group at the 74% similarity level. The protein patterns showed unexpectedly low similarity between subspecies "doylei" and the type strain of Campylobacter jejuni and revealed that some NNC strains were quite distinct from subspecies "doylei". Four electrophoretic (EP) types (I-IV) were identified from phenons formed at the 81% similarity level. Three of these (I, III, IV) corresponded to geographical location of strain isolation but the type II strains were from diverse locations. The correlation observed between EP-type, catalase production and sensitivity to 2, 3, 5, triphenyltetrazolium chloride indicated these latter two tests might be useful for biotyping within the subspecies.

Numerical analysis of electrophoretic protein patterns of Providencia alcalifaciens strains from human faeces and veterinary specimens.

Twenty-five strains of Providencia alcalifaciens from various countries have been characterized by one-dimensional SDS-PAGE of cellular proteins. They comprised 15 from human faeces, one from duck faeces, one from a guinea-pig eye and eight from unknown sources. Also included, for reference purposes, were the type strains of three other Providencia species. The protein patterns, which contained 45-50 discrete bands, were highly reproducible and were used as the basis for two numerical analyses. In the first, in which the principal protein bands (in the 33-40 kD range) were excluded, the 25 Prov. alcalifaciens strains formed, at the 83% S level, a single cluster whilst the three Providencia reference strains remained unclustered. In the second, which included all the protein bands, the 25 Prov. alcalifaciens strains formed 10 clusters at the 85% S level. We conclude that high resolution PAGE combined with computerized analysis of protein patterns provides the basis for typing clinical strains of Prov. alcalifaciens. Reference strains of each of the 10 PAGE types identified are available from NCTC for inclusion in future studies.

Numerical analysis of electrophoretic protein patterns of Providencia rustigianii strains from human diarrhoea and other sources.

Twenty strains of Providencia rustigianii (including the type strain of Prov. friedericiana) have been characterized by one-dimensional SDS-PAGE of cellular proteins. They comprised 12 strains (almost exclusively associated with the intestinal tract) from humans, plus eight largely from the intestinal tract of pig, penguin and environmental sources. The protein patterns, which contained 45-50 discrete bands, were highly reproducible and were used as the basis for two numerical analyses. In the first, which included all the protein bands, the 20 Prov. rustigianii strains formed six clusters at the 88% S level. One of these clusters included the type strains of both Prov. friedericiana and Prov. rustigianii, thereby confirming the synonymy of these two species. In the second analysis, the principal protein bands were excluded. At the 86% S level the 20 Prov. rustigianii strains formed a single cluster, whilst a field strain of Morganella morganii and the respective type strains of three other Providencia species remained unclustered. The total protein pattern of the type strain of Prov. alcalifaciens was very similar to that of Prov. rustigianii phenon 3 and the M. morganii field strain, which indicates that careful biochemical characterization may be necessary to ascribe strains to a species before typing by the PAGE technique. Alternatively, a selective analysis of the protein bands may be used to confirm the identity of the strains, as shown in this study.