Numerical analysis of sodium dodecyl sulphate-polyacrylamide gel electrophoretic protein patterns for the classification, identification and typing of medically important bacteria.

A numerical analysis of one-dimensional sodium dodecyl sulphate polyacrylamide gel electrophoretic protein patterns of three separate bacterial groups is described. Similarity between patterns was estimated using a correlation coefficient and is represented diagramatically by the unweighted pair-group with arithmetic averages method of clustering. Protein patterns were scanned using a laser densitometer interfaced directly to a microcomputer, where calculations were performed semi-automatically with specially written software. A method for the normalization of patterns from different gels is utilized. Whole cell protein patterns clearly distinguished strains representing various groups of Achromobacter. Similarly the two biovars of the Group EF-4 bacteria could be separated after analysis of partial "background patterns" as could the different species of Providencia. In addition, whole patterns could be used to type the various strains of P. rettgeri. These examples serve to illustrate the power, versatility and potential of the technique when applied to problems of classification, identification and typing of bacteria of medical interest. Its advantages and disadvantages, when compared to other available electrophoretic methodologies, are discussed, as is the future application of such technology to the hospital laboratory.