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Resistance of Streptococcus lactis mutants to beta-lactam antibiotics
Abstract:
Minimal inhibitory concentration and minimal bactericidal concentrations of penicillin and other beta-lactam antibiotics were determined for Streptococcus lactis in milk and trypteine soy broth. The values were always higher in milk than in broth. Minimal inhibitory concentration of penicillin was higher in solid than in liquid media. Two mutants resistant to penicillin and other beta-lactam antibiotics were obtained, and their growth rate, proteolysis, and acidification patterns determined. Tolerance toward these antibiotics was found when the mutants were grown in milk but not when they were grown in broth.
Insights
Penicillin and beta-lactam antibiotic resistance in Streptococcus lactis was higher in milk than broth. Resistant mutants showed tolerance in milk but not broth, impacting bacterial growth and acidification.
Area of Science:
- Microbiology
- Bacterial Resistance
- Food Science
Background:
- Streptococcus lactis is a key bacterium in dairy fermentation.
- Understanding its antibiotic resistance is crucial for food safety and starter culture development.
- Beta-lactam antibiotics are widely used, necessitating research into resistance mechanisms.
Purpose of the Study:
- To determine the minimal inhibitory and bactericidal concentrations of penicillin and other beta-lactam antibiotics for Streptococcus lactis.
- To investigate the characteristics of penicillin-resistant mutants of Streptococcus lactis.
- To assess antibiotic tolerance in different growth media.
Main Methods:
- Determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) in milk and trypteine soy broth.
- Isolation and characterization of two penicillin-resistant Streptococcus lactis mutants.
- Analysis of growth rate, proteolysis, and acidification patterns of wild-type and mutant strains.
Main Results:
- MIC and MBC values for beta-lactam antibiotics were consistently higher in milk compared to broth.
- Penicillin's MIC was also higher in solid media than liquid media.
- Resistant mutants exhibited tolerance to beta-lactam antibiotics in milk but not in broth.
Conclusions:
- Milk-based environments can influence the efficacy of beta-lactam antibiotics against Streptococcus lactis.
- Penicillin-resistant Streptococcus lactis mutants display conditional tolerance, dependent on the growth medium.
- These findings have implications for antibiotic use in dairy processing and managing bacterial resistance.