Affiliation:
1. Department of Bacteriology, National Bacteriological Laboratory, and Department of Bacteriology and Oral Microbiology, Karolinska Institute, Stockholm, Sweden
Abstract
Nine strains of
Bacteroides fragilis
were cultivated in stirred fermentors and tested for their ability to produce β-lactamase. There was a correlation between formation of β-lactamase and high values of the minimal inhibitory concentration against β-lactam antibiotics.
B. fragilis
strain B70 was used for optimizing the production of β-lactamase. The highest bacterial yield was obtained in a proteose peptone-yeast extract medium. Optimal conditions for growth and β-lactamase production were obtained at 37 C and pH 7.0. The β-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 β-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 β-lactamases from aerobic gram-negative species with regard to isoelectric points showed no similarities. Also the molecular weight of the β-lactamase from strain B70 of 43,000 indicates that this is a new class of β-lactamase.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
104 articles.
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