Overview
ISO 10705-1:1995 - Water quality: Enumeration of F-specific RNA bacteriophages defines a standard plaque-assay method for detecting and counting F-specific ribonucleic acid (RNA) bacteriophages in environmental samples. The method incubates samples with an appropriate host strain (typically Salmonella typhimurium WG49 or E. coli K‑12 Hfr), plates the mixture in semi-solid agar and reads visible plaques. Results are reported as the concentration of plaque‑forming particles (Cpfp) per unit volume. The standard applies to all types of water, sediments, sludges and shellfish extracts and flags F-specific RNA bacteriophages as indicators of wastewater contamination from human or animal feces.
Key topics and technical requirements
- Principle: Sample + host strain in semi-solid nutrient medium → incubation → count plaques (pfp).
- Scope of samples: surface water, groundwater, treated/untreated wastewater, sediments, sludges, shellfish extracts.
- Host strains and references: Salmonella typhimurium WG49 (NCTC 12484) and E. coli K‑12 Hfr (NCTC 12486 / ATCC 23631). Bacteriophage MS2 is referenced as a control phage (NCTC 12487 / ATCC 15597‑B1).
- Confirmatory testing: differential plating with RNase (commonly 40 µg/ml; 400 µg/ml in rare cases) to distinguish F‑specific RNA phages; antibiotic‑disk checks (nalidixic acid, kanamycin) and host recovery controls.
- Sensitivity and preconcentration: method can be used after sample dilution or, for low phage concentrations, after preconcentration (a separate part of ISO 10705 addresses concentration procedures).
- Quality control: turbidity calibration of host cultures, working and stock culture preparation, plaque count ranges (plates yielding 30–300 colonies for colony counts), and procedural blanks.
- Safety: handle host strains under appropriate biosafety procedures and avoid cross‑contamination, especially with high‑titre cultures.
Applications and users
- Environmental and public‑health laboratories monitoring water quality and viral pollution.
- Wastewater treatment operators validating disinfection and removal of viral indicators.
- Shellfish safety testing laboratories assessing viral contamination in shellfish extracts.
- Research groups studying enteric virus behavior, viral fate and transport, and environmental virology.
- Regulatory agencies using F‑specific RNA bacteriophages as fecal contamination indicators analogous to enteric viruses (e.g., norovirus, hepatitis A).
Related standards
- ISO 10705-2 - Enumeration of somatic coliphages (companion part).
- ISO 3696 - Water for analytical laboratory use.
- ISO 5667-1/2/3 - Water sampling (design, techniques, preservation/handling).
- ISO 6887 - Microbiology: preparation of dilutions.
- ISO 8199 - General guidance for enumeration of microorganisms by culture.
Keywords: ISO 10705-1:1995, F-specific RNA bacteriophages, water quality, detection and enumeration, plaque assay, wastewater indicator, Salmonella WG49, MS2 control, RNase confirmation.