EN ISO 7932:2004 PDF

Overview

EN ISO 7932:2004 - Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of presumptive Bacillus cereus - Colony-count technique at 30 °C - is a CEN-adopted ISO method for enumerating viable, presumptive B. cereus in foods, animal feeding stuffs and environmental samples from food production and handling areas. The standard defines a practical colony-count procedure using selective MYP agar and a restricted confirmatory stage (typical colony appearance on MYP and the haemolysis test), acknowledging that results are presumptive because closely related Bacillus spp. cannot always be fully differentiated.

Key topics and technical requirements

• Scope: Enumeration of viable presumptive B. cereus by colony-count at 30 °C; applicable to human food, animal feed and production environment samples.
• Principle: Surface plating of test sample or prepared initial suspension onto selective medium, incubation at 30 °C, colony counting and confirmation.
• Selective medium: MYP agar (mannitol-egg yolk-polymyxin) is specified; medium components and preparation steps are given in the standard.
• Incubation: Plates incubated aerobically at 30 °C for typically 18–48 hours.
• Confirmation: Restricted to typical colony morphology on MYP agar and haemolysis; termed “presumptive” because the confirmatory tests do not fully distinguish B. cereus from closely related species (e.g., B. anthracis, B. thuringiensis). A motility test may help differentiate B. cereus from B. anthracis when required.
• Optional heat treatment: A heat shock (e.g., 10 min at 80 °C) is noted as useful when spore counts are specifically required.
• Results & precision: Procedures for dilution, inoculation, colony counting, expression of results and precision data from interlaboratory trials are included.

Applications and users

This standard is valuable for:

• Food and feed industry quality control laboratories performing routine microbial enumeration.
• Environmental monitoring teams in food production and catering facilities.
• Public health and regulatory laboratories assessing contamination and compliance.
• Contract testing labs and auditors specifying reproducible, standardized methods for Bacillus cereus enumeration.

Practical applications include product safety testing, shelf-life studies, hygiene monitoring, process verification and investigation of suspected foodborne illness linked to B. cereus.

Related standards

• ISO 6887-1: Preparation of test samples and decimal dilutions
• ISO 7218: General rules for microbiological examinations
• ISO/TS 11133-2: Guidelines on preparation and performance testing of culture media

EN ISO 7932:2004 provides a harmonized, practical colony-count technique for presumptive B. cereus detection that supports consistent food microbiology testing and regulatory compliance.