Formation of beta-lactamase in Bacteroides fragilis: cell-bound and extracellular activity

Antimicrob Agents Chemother. 1976 May;9(5):727-35. doi: 10.1128/AAC.9.5.727.

Abstract

Nine strains of Bacteroides fragilis were cultivated in stirred fermentors and tested for their ability to produce beta-lactamase. There was a correlation between formation of beta-lactamase and high values of the minimal inhibitory concentration against beta-lactam antibiotics. B. fragilis strain B70 was used for optimizing the production of beta-lactamase. The highest bacterial yield was obtained in a proteose peptone-yeast extract medium. Optimal conditions for growth and beta-lactamase production were obtained at 37 C and pH 7.0. The beta-lactamase was released into the surrounding medium during the growth period to about 50%. Osmotic shock released about 20% of the total activity, and remaining activity was found in the cytoplasmic fraction. Substrate profile studies on four beta-lactamase-producing strains showed that the enzymes were mainly cephalosporinases. They are inhibited by cloxacillin, p-chloromercuribenzoate, and iodine. Analytical isoelectric focusing in polyacrylamide gel gave an isoelectric point of 4.9 +/- 0.2 for three of the strains and 5.6 +/- 0.2 for one. Comparison with beta-lactamases from aerobic gram-negative species with regard to isoelectric points showed no similarities. Also the molecular weight of the beta-lactamase from strain B70 of 43,000 indicates that this is a new class of beta-lactamase.

MeSH terms

  • Bacteroides fragilis / enzymology*
  • Bacteroides fragilis / growth & development
  • Bacteroides fragilis / ultrastructure
  • Culture Media
  • Hydrogen-Ion Concentration
  • Isoelectric Focusing
  • Molecular Weight
  • Penicillinase / analysis
  • Penicillinase / biosynthesis*
  • Temperature
  • beta-Lactamase Inhibitors

Substances

  • Culture Media
  • beta-Lactamase Inhibitors
  • Penicillinase