Overview
EN ISO 7899-2:2000 (ISO 7899-2:2000) specifies a standardized membrane filtration method for the detection and enumeration of intestinal enterococci in water. Intended primarily for clean or disinfected waters - such as drinking water and swimming pool water - the standard describes filtration, selective culture, confirmation and reporting procedures to assess faecal contamination in water quality monitoring.
Key topics and technical requirements
- Scope and applicability
- Designed for examination of drinking, pool and other low-turbidity waters; not recommended where heavy suspended solids or interfering microflora are present.
- Principle
- Filter a measured sample through a 0.45 μm membrane; incubate on a selective medium that reveals enterococci via reduction of TTC to red formazan.
- Selective media and reagents
- Primary medium: Slanetz and Bartley medium (complete medium includes TTC indicator).
- Confirmation medium: bile‑aesculin‑azide agar; positive colonies hydrolyse aesculin producing a tan-to-black reaction.
- Note: media contain sodium azide (toxic); follow handling and disposal precautions.
- Critical parameters
- Membrane pore size: 0.45 μm.
- Incubation: primary plates at 36 °C ± 2 °C for 44 h ± 4 h.
- Confirmation: transfer membranes to bile‑aesculin‑azide agar preheated to 44 °C ± 0.5 °C and incubate 2 h.
- Typical target organisms: E. faecalis, E. faecium, E. durans, E. hirae (occasionally other Enterococcus or Streptococcus species).
- Sampling and sample handling
- Follow ISO 5667 series for sampling; begin examination preferably within 6 h of collection (or store at 5 °C ± 3 °C up to 24 h in exceptional cases).
- Quality assurance and reporting
- Laboratories must maintain quality control of reagents, membranes and procedures. Results should be calculated per ISO 8199 and reported with full sample identification and any deviations.
Practical applications and users
- Used for routine monitoring of drinking water, recreational waters, pool compliance, and for microbiological investigations of suspected faecal contamination.
- Typical users: water utilities, public health laboratories, environmental testing labs, pool operators, regulatory agencies, and consulting microbiologists focused on water quality and microbiology of water.
Related standards
- ISO 8199 - general guidance for enumeration of micro-organisms by culture.
- ISO 5667 series - sampling guidance.
- ISO 3696 - water for analytical laboratory use.
- ISO 6887-1, ISO 7704 - sample preparation and membrane filter evaluation.
Keywords: EN ISO 7899-2:2000, ISO 7899-2:2000, membrane filtration method, intestinal enterococci, water quality, Slanetz and Bartley, bile-aesculin-azide agar, sodium azide, TTC, microbiology of water.
