Beta-lactamase-mediated resistance and opportunities for its control

J Antimicrob Chemother. 1998 Jun:41 Suppl D:25-41. doi: 10.1093/jac/41.suppl_4.25.

Abstract

Clinical use of beta-lactams has selected for beta-lactamase-producing organisms. Numerous beta-lactamases are known, and sequencing allows them to be divided into four Classes, A to D, with Classes A and C being the most important. Pharmaceutical chemists have responded to the spread of beta-lactamase-producing organisms by developing stable agents and inhibitors. Stability in penicillins and cephalosporins is achieved by attaching a bulky substituent to the amino group of 6-aminopenicillanic acid or 7-aminocephalosporanic acid, or by replacing the hydrogen on carbon 6 (penicillins) or 7 (cephalosporins) with an alpha-methoxy group. In carbapenems, stability is achieved by incorporation of a simple trans-6-hydroxyethyl group. Beta-lactamase-inhibitory activity occurs in many beta-lactam classes but only clavams and penicillanic acid sulphones have been developed specifically as beta-lactamase inhibitors. These inhibit most Class A and some Class D enzymes but act poorly against Class B and C enzymes. Their success is affected by the amount of enzyme, the permeability of the bacterial cell wall, the partner beta-lactam and the pH. Piperacillin/tazobactam, which combines a good inhibitor of Class A enzymes with a broad-spectrum, easily-protected penicillin, has wide activity against common pathogens, the major exceptions being strains of Enterobacter, Serratia and Citrobacter freundii that produce large amounts of Class C enzymes, and Gram-positive cocci with modified penicillin-binding proteins. Beta-lactamase-stable beta-lactams and inhibitor combinations overcome many existing resistance mechanisms but are themselves selecting new resistances. Few new beta-lactams able to overcome these resistances are advanced in development and consequently the opportunities for control lie mostly in the more prudent use of compounds already available.

Publication types

  • Review

MeSH terms

  • Anti-Bacterial Agents / chemistry*
  • Anti-Bacterial Agents / pharmacology
  • Bacteria / drug effects
  • Bacteria / enzymology*
  • beta-Lactam Resistance*
  • beta-Lactamase Inhibitors
  • beta-Lactamases / metabolism*
  • beta-Lactams

Substances

  • Anti-Bacterial Agents
  • beta-Lactamase Inhibitors
  • beta-Lactams
  • beta-Lactamases