Overview
EN ISO 9308-1:2014/A1:2017 is the CEN-endorsed amendment to ISO 9308-1:2014 and prescribes the membrane filtration method for the enumeration of Escherichia coli and coliform bacteria in waters with low bacterial background flora. The amendment (A1:2016) was approved by CEN as EN ISO 9308-1:2014/A1:2017 and clarifies incubation and agar performance requirements to support consistent laboratory results and regulatory compliance.
Key Topics
- Membrane filtration procedure: The method uses membrane filtration to retain bacterial cells from a water sample before culturing on selective chromogenic media.
- Chromogenic Coliform Agar (CCA): The document specifies placement of membranes on CCA and details performance testing criteria for the medium.
- Incubation conditions: Membranes on CCA are incubated at (36 ± 2) °C for 21 to 24 h (as amended), ensuring reproducible colony development for enumeration.
- CCA performance testing: The amendment replaces the referenced table for CCA performance. Key characteristics include:
- Productivity: Expected recovery for target strains (example: E. coli) with a productivity ratio (PR) ≥ 0.7.
- Colony reactions: Typical colour reactions are defined (e.g., E. coli: dark‑blue to violet colonies; Enterobacter aerogenes: pink to red colonies).
- Selectivity and specificity checks: Inhibition of non‑target organisms and confirmation of colourless colonies for certain non‑coliforms are addressed.
- Reference strains and traceability: The amendment refers to standard culture collection strain numbers for performance verification.
Applications
This standard is essential for laboratories and organizations involved in water quality monitoring, public health surveillance, and regulatory compliance. Typical applications include:
- Routine testing of drinking, recreational and environmental waters where low bacterial background is expected.
- Verification of water treatment efficacy and distribution system surveillance.
- Reference method for compliance testing in jurisdictions that adopt EN ISO 9308-1:2014/A1:2017.
The clear incubation regime and CCA performance criteria help ensure reliable, comparable results across accredited testing facilities.
Related Standards
- ISO 9308-1:2014 - Base international standard for membrane filtration enumeration of E. coli and coliforms.
- EN ISO 9308-1:2014/A1:2017 - CEN endorsement of the ISO 2016 amendment (A1) without modification.
- ISO/TC 147 & CEN/TC 230 - Technical committees responsible for water quality and water analysis methods.
For laboratories and water quality professionals, EN ISO 9308-1:2014/A1:2017 provides a robust, standardized approach to enumerate E. coli and coliforms using membrane filtration and chromogenic media, supporting actionable monitoring and regulatory decision‑making.
