Evaluation of BD BBL CHROMagar Staph aureus medium using AOAC and ISO culture methods. Performance tested method...

Area of Science:

• Food Microbiology
• Microbial Detection Methods

Background:

• Accurate detection of Staphylococcus aureus is crucial for food safety.
• Existing methods for S. aureus enumeration can be time-consuming and require validation.

Purpose of the Study:

• To evaluate the performance of BBL CHROMagar Staph aureus (CSA) medium for isolating and enumerating S. aureus.
• To compare CSA against established AOAC and ISO reference methods in various food matrices.

Main Methods:

• Internal and external validation of CSA medium.
• Comparison with Baird-Parker reference media using AOAC Official Method 975.55 and ISO 6888-1:1999.
• Statistical analysis of bacterial counts (log10 transformed) across low, medium, and high contamination levels.

Main Results:

• No statistical difference in S. aureus recovery between CSA and AOAC methods across all food types and contamination levels.
• CSA showed comparable results to the ISO method, except for low-level smoked salmon where it recovered more colonies in internal testing.
• High correlation coefficients (92.6-99.4%) and 100% sensitivity and specificity were observed.

Conclusions:

• CSA medium is an effective and reliable tool for the isolation, enumeration, and presumptive identification of S. aureus.
• The medium provides accurate results within 24 hours for cooked roast beef, smoked salmon, and shell eggs.
• CSA offers a viable alternative to traditional methods, meeting ISO and AOAC standards.