Identification of -Lactamases by Analytical Isoelectric Focusing: Correlation with Bacterial Taxonomy

Abstract

.beta.-Lactamases (EC 3.5.2.6) can be directly compared by analytical isoelectric focusing. Using this technique, 242 strains from 5 gram-positive and 16 gram-negative genera were examined. A preparation of each strain focused as a single group of bands which did not match the pattern of any R factor-associated .beta.-lactamase. None of the strains was known to carry an R factor and resistance transfer experiments were unsuccessful. The enzymes studied were therefore thought to be chromosomally mediated. The isoelectric points ranged from 3.9-8.7 and were not related to the substrate profiles or other biochemical properties. The chromosomal .beta.-lactamases appeared to be specific for genus, species and sub-species, and strains that produced identical .beta.-lactamases had identical bacterial characteristics. Correlation of bacteriological differences with differences in .beta.-lactamase patterns is discussed with particular reference to strains of Escherichia coli and Klebsiella spp. Since .beta.-lactamases may be universally produced by bacteria, separation of the enzymes by analytical isoelectric focusing could be used in bacterial taxonomy.