Overview
EN ISO 10705-3:2024 (identical to ISO 10705-3:2003) defines the principles for validating methods that concentrate bacteriophages from water prior to detection and enumeration. The standard addresses when and how to concentrate large-volume water samples (from 100 ml up to several litres) into smaller analytical volumes (typically a few ml up to 20 ml) so that phage assays (plaque-forming particles, pfp) can be carried out reliably. Concentration is recommended when samples are expected to contain less than 3 pfp per millilitre. Annex A lists example concentration techniques and their suitable fields of application.
Key topics and technical requirements
- Scope and applicability: Applies to all kinds of water provided suspended solids or dissolved matter do not interfere with the concentration step.
- Validation principle: Evaluate a concentration method by determining phage recovery and reproducibility using samples spiked with naturally polluted water (e.g., primary or treated sewage).
- Sampling guidance: Samples up to 10 L are routinely transportable; for larger volumes, initial concentration in the field is recommended. Transport and storage of intermediate concentrates must be included in validation.
- Spiking and controls: Prepare sewage spiking material (centrifuge at ~1 000 g for 20 min or filter through 8–12 µm), aim for target seeding concentrations (example ranges 60–200 pfp/ml before aliquoting), add 5% glycerol for storage, freeze at specified temperatures and verify homogeneity.
- Analytical quality: Assess recovery across volumes and turbidity levels, monitor reproducibility and within/between-batch variation (statistical tests such as Cochran’s dispersion are referenced).
- Safety and equipment: Follow microbiological laboratory safety; some concentration steps may involve pressure - observe relevant precautions.
- Non-prescriptive: The standard does not mandate specific concentration techniques but provides the validation framework; Annex A offers representative methods proven satisfactory.
Applications and users
- Environmental and water-quality laboratories validating phage concentration workflows for routine monitoring.
- Wastewater and drinking-water surveillance teams assessing viral indicators.
- Research groups developing or comparing phage concentration methods (filtering, precipitation, adsorption-elution, etc.).
- Public health agencies, consultants, and method developers implementing standard-compliant protocols for bacteriophage recovery and enumeration.
Related standards
Keywords: EN ISO 10705-3:2024, bacteriophages, water quality, concentration methods, phage concentration validation, plaque-forming particles, water microbiology.