Overview
EN ISO 22118:2011 (ISO 22118:2011) defines minimum performance characteristics for molecular methods based on the polymerase chain reaction (PCR) used to detect and quantify food‑borne pathogens. The standard applies to detection in foodstuffs, isolates from foods, environmental samples and animal feeding stuffs. It sets out requirements for method scope, reporting of performance data and validation evidence so laboratories, method developers and regulators can compare molecular methods reliably.
Key Topics and Requirements
- Scope and purpose - Specifies intended use, limitations and that criteria in the standard are met before method deployment.
- Performance reporting - Method providers must supply empirical data from single‑ or multi‑laboratory trials and pre‑validation experiments (parameter/reagent variation).
- Selectivity (specificity)
- Inclusivity: test target variants; where possible test up to 50 target strains to demonstrate detection across sequence variants.
- Exclusivity: test non‑target organisms. For bacterial assays select a minimum of 30 non‑target strains (≥90% bacteria; remainder yeasts, moulds or viruses). For fungal assays similar proportions with fungi predominant; virus assays should include at least three non‑target viruses.
- Use a detectable nucleic acid amount (e.g., DNA representing ~10 cells) for selectivity testing and confirm suitability of nucleic acid controls.
- Sensitivity
- Qualitative detection minimums: 1–10 cells per assay for bacteria/parasites; 10–100 particles or genome equivalents for viruses (relative to defined sample amount, before enrichment).
- Defines Limit of Detection (LOD) and Limit of Quantification (LOQ) and requires reporting of detection range.
- Precision and trueness - Defines precision concepts (repeatability, reproducibility) and trueness (closeness to true value).
- Robustness testing - Assess method tolerance to small procedural/environmental changes.
- Scientific basis - Methods should include principle overview and references to supporting literature.
Applications
- Validation and acceptance of PCR and real‑time PCR assays for food safety testing.
- Method development and performance assessment by diagnostic kit manufacturers.
- Reference for accredited testing laboratories implementing molecular assays.
- Support for regulatory bodies and food producers evaluating detection limits and specificity of assays.
Related Standards
- ISO 22174:2005 - PCR general requirements and definitions
- ISO 22119 - Real‑time PCR general requirements and definitions
- ISO 20836 / 20837 / 20838 - Related PCR method validation and sample/thermal cycler requirements
- ISO/TS 13136 - (in preparation) STEC real‑time PCR horizontal method
Keywords: ISO 22118, EN ISO 22118:2011, PCR for food‑borne pathogens, performance characteristics, food microbiology, limit of detection, limit of quantification, inclusivity exclusivity, method validation.
