EN ISO 7932:2004/A1:2020 PDF

Overview

EN ISO 7932:2004/A1:2020 is a CEN-endorsed amendment to ISO 7932:2004 that defines the horizontal colony‑count technique at 30 °C for the enumeration of presumptive Bacillus cereus in food and animal feeding stuffs. Amendment A1 (2020) updates the standard by including optional confirmatory and characterization tests for isolates (referred to as the B. cereus group to reflect taxonomic diversity). The amendment was approved by CEN in March 2020 and integrates validated laboratory procedures in new annexes.

Key topics and requirements

• Primary method: Horizontal colony‑count technique at 30 °C for enumeration of presumptive B. cereus (original ISO 7932 method remains the base method).
• Terminology update: Uses the term “B. cereus group” (note on phylogenetic diversity and multiple species).
• Optional tests (Annexes C–F) for isolates obtained after colony counting:
  • PCR detection of cytK-1 / cytK-2 variants (cytotoxin K) to identify cytK variants and to confirm Bacillus cytotoxicus using validated primers and amplification conditions.
  • PCR detection of the ces gene (cereulide synthetase) to screen for cereulide‑producing, emetic toxin–producing strains.
  • Motility test for preliminary screening of presumptive B. anthracis (noting limitations; meant for screening, not definitive identification).
  • Microscopic examination of parasporal crystals to identify B. thuringiensis.
• Laboratory requirements: Annexes supply reagent lists, equipment recommendations (PCR cyclers, agarose electrophoresis, nucleic acid extraction tools), controls and validated protocols. The amendment references relevant molecular standards (e.g., ISO 20837, ISO 20838, ISO 22174) for good laboratory practice.
• Use of validated methods: Optional tests are intended as complementary/epidemiological investigations and include validated workflows and controls.

Applications and users

This standard is essential for:

• Food microbiology laboratories performing routine enumeration and follow‑up characterization of B. cereus group isolates.
• Food manufacturers and safety teams monitoring product safety, shelf‑life and contamination sources.
• Public health and regulatory authorities conducting outbreak investigations and surveillance of emetic or enterotoxigenic strains.
• Research laboratories studying strain diversity, virulence markers (cytK, ces) and taxonomy within the B. cereus group.

Keywords: EN ISO 7932:2004/A1:2020, Bacillus cereus enumeration, colony‑count technique 30 °C, B. cereus group, PCR cytK, ces gene, cereulide, food microbiology standard.

Related standards

• ISO 18465 - cereulide quantification
• ISO 20837, ISO 20838, ISO 22174 - molecular biology method guidance and reagent/equipment standards

This amendment integrates molecular and phenotypic optional tests to strengthen identification and risk assessment of B. cereus group isolates in food safety workflows.