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Broad spectrum beta-lactamases of Citrobacter diversus
B Oliva1, B Segatore, G Amicosante
1Department of Biomedical Sciences, University of L'Aquila, Italy.
The Journal of Antimicrobial Chemotherapy
|March 1, 1990
Summary
Citrobacter diversus NF85 produces inducible beta-lactamase enzymes. Mutants revealed distinct enzyme profiles and antibiotic resistance patterns, including a novel beta-lactamase form in derepressed strains.
Area of Science:
- Microbiology
- Enzymology
- Genetics
Background:
- Citrobacter diversus NF85 harbors a chromosomal beta-lactamase.
- Beta-lactamase activity is inducible by various beta-lactam antibiotics.
- Two primary beta-lactamase forms (pI 5.7, 6.2) exist in crude cell extracts.
Purpose of the Study:
- To investigate the characteristics of beta-lactamase production in Citrobacter diversus NF85.
- To analyze the impact of mutations on beta-lactamase expression and antibiotic resistance.
- To identify novel beta-lactamase forms in derepressed mutants.
Main Methods:
- Induction of beta-lactamase with various beta-lactam antibiotics.
- Generation of derepressed mutants using nitrosoguanidine.
- Isoelectric focusing (pI) to characterize beta-lactamase forms.
- Determination of antibiotic resistance profiles.
Main Results:
- Mutants exhibited varied beta-lactamase expression levels compared to the parent strain.
- Derepressed mutants displayed altered resistance patterns to diverse beta-lactam antibiotics.
- A novel beta-lactamase (pI 6.8) was identified in totally derepressed mutants expressing high, constitutive levels of enzyme.
Conclusions:
- Nitrosoguanidine mutagenesis effectively generated derepressed beta-lactamase mutants in C. diversus NF85.
- Mutations significantly influence beta-lactamase expression and confer distinct antibiotic resistance phenotypes.
- The identification of a new beta-lactamase form highlights the genetic complexity of beta-lactamase regulation.