ISO 6461-2:1986 PDF

Water quality — Detection and enumeration of the spores of sulfite-reducing anaerobes (clostridia) — Part 2: Method by membrane filtration

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Title (English):

ISO 6461-2:1986

Water quality — Detection and enumeration of the spores of sulfite-reducing anaerobes (clostridia) — Part 2: Method by membrane filtration

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 3
Publication date:: February 6, 1986
Edition:: ISO IS 6461 edition 1 version 1
ICS:: 07.100.20

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Description (English):

The procedure is applicable to all types of water, except when a large amount of particulate material is liable to be retained by the membrane. The principle covers several steps from selection by applying heat to destroy vegetative bacteria to filtration of the water sample through a membrane filter having a suitable pore size (0,2 µm) to retain the spores in or on it. The filter is placed on a selective culture medium, followed by incubation and counting of black colonies.

Technical details

Technical committee: ISO/TC 147/SC 4 - Microbiological methods
SKU: ISO 6461-2:1986

Abstract

Overview

ISO 6461-2:1986 is an international standard developed by the International Organization for Standardization (ISO) that specifies a membrane filtration method for detecting and enumerating spores of sulfite-reducing anaerobes (clostridia) in water. These spores are key microbiological indicators due to their resistance to environmental stress and common water treatment procedures, making them valuable in assessing water quality and possible fecal contamination. The standard applies broadly to various types of water except when excessive particulate material would clog the membrane filter.

This method is designed to provide reliable and reproducible detection of clostridial spores, offering essential support for water quality monitoring and safety assurance.

Key Topics

Scope of Application Suitable for examining all types of water, including drinking water, surface water, well water, and mineral waters. It excludes samples with high particulate content that could obstruct membrane filtration.
Method Principle
- Heat Selection: Samples undergo heat treatment at 75 ± 5°C for 15 minutes to eliminate vegetative bacteria, selecting for heat-resistant spores.
- Membrane Filtration: The heat-treated water is filtered through a membrane with 0.2 µm pore size to retain spores.
- Culturing: The membrane is placed on a selective sulfite-iron agar medium. This medium includes nutrient agar enhanced with sodium sulfite and iron sulfate, promoting growth and visualization of sulfite-reducing clostridia.
- Incubation: Plates are incubated anaerobically at 37 ± 1°C for 20 ± 4 hours and again for 44 ± 4 hours.
- Enumeration: Spores are identified by counting characteristic black colonies formed on the selective medium.
Culture Media and Reagents
- Nutrient agar enriched with sodium sulfite and iron(III) sulfate.
- Alternative media such as tryptose-sulfite-agar may be used.
- Preparation and quality control of media and reagents are critical for consistent results.
Sampling and Reporting
- Sample volumes vary depending on water contamination level, typically 100 ml for low contamination and less for highly polluted water.
- Results are expressed as the number of spores per volume of water, typically referring to the 44-hour incubation count.
- The test report must include method details, sample identification, and any deviations or incidents affecting results.

Applications

Abstract

Overview

This method is designed to provide reliable and reproducible detection of clostridial spores, offering essential support for water quality monitoring and safety assurance.

Key Topics

Scope of Application Suitable for examining all types of water, including drinking water, surface water, well water, and mineral waters. It excludes samples with high particulate content that could obstruct membrane filtration.
Method Principle
- Heat Selection: Samples undergo heat treatment at 75 ± 5°C for 15 minutes to eliminate vegetative bacteria, selecting for heat-resistant spores.
- Membrane Filtration: The heat-treated water is filtered through a membrane with 0.2 µm pore size to retain spores.
- Culturing: The membrane is placed on a selective sulfite-iron agar medium. This medium includes nutrient agar enhanced with sodium sulfite and iron sulfate, promoting growth and visualization of sulfite-reducing clostridia.
- Incubation: Plates are incubated anaerobically at 37 ± 1°C for 20 ± 4 hours and again for 44 ± 4 hours.
- Enumeration: Spores are identified by counting characteristic black colonies formed on the selective medium.
Culture Media and Reagents
- Nutrient agar enriched with sodium sulfite and iron(III) sulfate.
- Alternative media such as tryptose-sulfite-agar may be used.
- Preparation and quality control of media and reagents are critical for consistent results.
Sampling and Reporting
- Sample volumes vary depending on water contamination level, typically 100 ml for low contamination and less for highly polluted water.
- Results are expressed as the number of spores per volume of water, typically referring to the 44-hour incubation count.
- The test report must include method details, sample identification, and any deviations or incidents affecting results.

ISO 6461-2:1986 PDF

Technical details

Abstract

Overview

Key Topics

Applications

Abstract

Overview

Key Topics

Applications

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