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Published on: September 30, 2014
Beta-lactamase-producing mutants of Streptococcus cremoris
1Department of Microbiology, Oregon State University, Corvallis 97331-3804.
Journal of Dairy Science
|August 1, 1987
Summary
Penicillin-resistant Streptococcus cremoris mutants were developed for cheese production. These mutants produce beta-lactamase, conferring resistance to penicillin and related antibiotics, with stable resistance observed over passages.
Area of Science:
- Food Microbiology
- Bacteriology
- Antibiotic Resistance
Background:
- Streptococcus cremoris is crucial for Cheddar cheese fermentation.
- Penicillin is used to control spoilage organisms but can affect starter cultures.
- Developing penicillin-resistant strains could improve cheese production consistency.
Purpose of the Study:
- To isolate and characterize penicillin-resistant mutants of Streptococcus cremoris.
- To investigate the mechanism of penicillin resistance in these mutants.
- To assess the stability and phage sensitivity of the resistant strains.
Main Methods:
- Induction of mutations using N-methyl-N-nitro-N-nitrosoguanidine.
- Determination of minimal inhibitory concentrations for penicillin G and beta-lactam antibiotics.
- Assay for beta-lactamase production.
- Plasmid DNA analysis and phage sensitivity testing.
Main Results:
- Six penicillin-resistant mutants of S. cremoris were successfully isolated.
- Resistant mutants showed a 50-fold increase in minimal inhibitory concentration for penicillin G.
- Resistance was attributed to beta-lactamase production; plasmid DNA was not detected.
- Mutants exhibited altered phage sensitivity patterns but retained resistance after 20 passages.
Conclusions:
- Penicillin-resistant Streptococcus cremoris mutants can be generated and maintain resistance.
- Beta-lactamase production is the primary mechanism for penicillin resistance in these strains.
- These resistant mutants have potential applications in cheese manufacturing to mitigate penicillin contamination issues.
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