The use of analytical isoelectric focusing for detection and identification of beta-lactamases

J Gen Microbiol. 1975 May;88(1):169-78. doi: 10.1099/00221287-88-1-169.


BETA-Lactamases (EC. from strains of Gram-negative bacteria have been studied using analytical isoelectric focusing. This permits a visual comparison of the patterns of beta-lactamase bands produced by enzymes from different organisms. Purification of crude intracellular preparations is unnecessary and the technique is sufficiently sensitive to demonstrate beta-lactamase in mutants previously reported to lack the enzyme. R that have not been distinguished from one another biochemically or immunologically can be differentiated by isoelectric focusing. Conversely, the enzymes specified by the R factors RTEM, R1 and RGN14, with identical isoelectric focusing patterns have the same biochemical properties. Chromosomal and R-factor-mediated beta-lactamases from single strains have been separated and their identities confirmed by immunoisoelectric focusing. R factor-mediated enzymes gave identical isoelectric focusing patterns irrespective of the host strain. Isoelectric focusing can therefore be used to observe the transfer of beta-lactamases carried by R factors.

MeSH terms

  • Amidohydrolases / isolation & purification*
  • Anti-Bacterial Agents / pharmacology
  • Bacteria / enzymology*
  • Cell-Free System
  • Cephalosporinase / isolation & purification*
  • Cephalosporinase / metabolism
  • Conjugation, Genetic
  • Drug Resistance, Microbial
  • Enterobacteriaceae / enzymology
  • Escherichia coli / drug effects
  • Escherichia coli / enzymology
  • Isoelectric Focusing* / methods
  • Klebsiella / enzymology
  • Mutation
  • Penicillinase / isolation & purification*
  • Penicillinase / metabolism
  • Proteus / enzymology
  • Proteus mirabilis / enzymology
  • Pseudomonas aeruginosa / enzymology
  • Species Specificity
  • beta-Lactams / pharmacology


  • Anti-Bacterial Agents
  • beta-Lactams
  • Amidohydrolases
  • Cephalosporinase
  • Penicillinase