ISO 6888-3:2003

Overview

ISO 6888-3:2003 - "Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of coagulase-positive staphylococci - Part 3" - specifies a horizontal laboratory method using the Most Probable Number (MPN) technique for the detection and enumeration of coagulase-positive staphylococci (primarily Staphylococcus aureus, but also S. intermedius and some S. hyicus strains). The standard is intended for products for human consumption, animal feed and environmental samples in food production/handling areas and is recommended where staphylococci are stressed and present at low numbers (e.g., dried products).

Key topics and technical requirements

• Scope: Detection and MPN enumeration of coagulase-positive staphylococci in food, feed and environmental samples.
• Principle: Inoculation of selective liquid medium (e.g., modified Giolitti and Cantoni broth) followed by anaerobic incubation at 37 °C (24 h and 48 h). Presumptive positives are identified by potassium tellurite reduction and then plated onto selective solid media.
• Confirmation: Presumptive colonies are confirmed by coagulase reaction or via rabbit plasma fibrinogen agar (specific plasma reaction).
• Enumeration: Enumeration is by the Most Probable Number (MPN) technique - confirmed positive dilutions are used to calculate the MPN per g or ml.
• Media & reagents: The standard gives preparation and quality requirements for diluents, modified Giolitti and Cantoni broth, potassium tellurite solution, agar and references Baird‑Parker and rabbit plasma fibrinogen media.
• Quality assurance: Performance testing and selectivity/productivity criteria are referenced (ISO/TS 11133 and ISO 7218). Anaerobiosis can be achieved by agar/paraffin plugs or incubation jars.

Practical applications

• Routine food safety testing where low-level or stressed S. aureus is expected (e.g., dried foods, spices, powdered milk).
• Regulatory and compliance testing for food and feed microbiology.
• Environmental monitoring in food processing and handling areas to detect contamination sources.
• Verification and validation of cleaning, processing and storage controls where low counts may still pose a risk.

Who should use this standard

• Food and feed microbiology laboratories (QC/analytical labs)
• Public health and regulatory agencies
• Food manufacturers and contract testing providers
• Laboratory staff involved in microbiological method selection and validation

Related standards

• ISO 6888-1:1999 - Technique using Baird‑Parker agar
• ISO 6888-2:1999 - Technique using rabbit plasma fibrinogen agar
• ISO 6887 (sample preparation), ISO 7218 (general microbiology rules), ISO 8261, ISO/TS 11133 (culture media QA)

Keywords: ISO 6888-3:2003, coagulase-positive staphylococci, Staphylococcus aureus, most probable number (MPN), food microbiology, detection and enumeration, Baird-Parker, modified Giolitti and Cantoni broth, rabbit plasma fibrinogen agar.