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Updated: Sep 3, 2026
Improved Enzyme Protection Assay to Study Staphylococcus aureus Internalization and Intracellular Efficacy of Antimicrobial Compounds
Published on: September 8, 2021
Abstract:
Most media have been unreliable when used to determine the number of coagulase-positive staphylococci in meat pot pies in the presence of overwhelming numbers of Bacillus cells. Various metabolic inhibitors were tested to determine whether they would suppress the growth of Bacillus cells without appreciably affecting the staphylococcal growth. The use of Staphylococcus Medium No. 110 modified by the addition of 0.75 mM sodium azide appears to be practical for the isolation of small numbers of coagulase-positive staphylococci from frozen meat pot pies.
Insights
A modified Staphylococcus Medium No. 110 with sodium azide effectively suppresses Bacillus growth, enabling accurate detection of coagulase-positive staphylococci in meat pot pies.
Area of Science:
- Food Microbiology
- Bacteriology
- Analytical Methods
Background:
- Accurate enumeration of coagulase-positive staphylococci in food is crucial for public health.
- Existing culture media often yield unreliable results for staphylococci in the presence of high levels of Bacillus species in meat pot pies.
Purpose of the Study:
- To identify a selective agent to inhibit Bacillus growth while allowing Staphylococcus growth.
- To develop a practical method for isolating coagulase-positive staphylococci from contaminated meat pot pies.
Main Methods:
- Testing various metabolic inhibitors to suppress Bacillus growth.
- Modifying Staphylococcus Medium No. 110 with selected inhibitors.
- Evaluating the efficacy of the modified medium for isolating staphylococci from frozen meat pot pies.
Main Results:
- Sodium azide at 0.75 mM was found to effectively inhibit Bacillus cell proliferation.
- The modified Staphylococcus Medium No. 110 demonstrated practicality for isolating coagulase-positive staphylococci.
- This method allows for the detection of staphylococci even when outnumbered by Bacillus cells.
Conclusions:
- Staphylococcus Medium No. 110 supplemented with 0.75 mM sodium azide is a practical and effective medium for isolating coagulase-positive staphylococci from meat pot pies.
- This advancement improves the reliability of microbiological testing in complex food matrices.
