SIST EN ISO 9308-2:2014 PDF

Overview

SIST EN ISO 9308-2:2014 specifies a standardized method for the enumeration of Escherichia coli (E. coli) and coliform bacteria in water, using the Most Probable Number (MPN) technique. Developed by the European Committee for Standardization (CEN) and aligned with ISO 9308-2:2012, this method is fundamental in water quality microbiology, supporting public health and environmental monitoring by providing reliable detection of faecal contamination.

The method involves incubating water samples with a specific liquid growth medium, identifying positive reactions indicative of E. coli and coliforms, and calculating bacterial concentrations using MPN statistical tables. This approach is effective for a broad range of water types, including those with suspended matter and high background microorganisms, making it highly adaptable for laboratory use.

Key Topics

• MPN Method Principle: Utilizes statistical probability to estimate bacteria concentrations based on the number of positive reactions in multiple test wells, improving accuracy, especially when precise counts are not feasible.
• Target Organisms Detection: Relies on the expression of the enzyme β-D-glucuronidase to specifically confirm E. coli presence. Coliform bacteria are identified through the presence of β-D-galactosidase.
• Sample Types and Limitations:
  • Applicable to drinking water, surface water, groundwater, and waste water.
  • Not suitable for coliform enumeration in marine water without prior dilution due to high salt content. For E. coli in marine samples, a 1:10 dilution in sterile water is generally required.
• Device and Media:
  • Employs readily available commercial media and devices (e.g., Quanti-Tray systems).
  • Enables simultaneous detection and enumeration of indicators.
• Interpretation and Reporting:
  • Positive results can be read visually or under UV light.
  • The method produces confirmed results for E. coli and coliforms, with no further confirmation of positives required.

Applications

SIST EN ISO 9308-2:2014 is widely implemented for microbiological water quality assessment in:

• Drinking Water Monitoring: Ensures compliance with health regulations by detecting faecal contamination.
• Environmental Surveillance: Supports routine monitoring of lakes, rivers, reservoirs, and groundwater.
• Wastewater Testing: Evaluates treatment efficacy and environmental impact of effluent discharges.
• Emergency Response: Quickly assesses contamination following environmental incidents or infrastructure failures.
• Industrial Water Quality Control: Used in food, beverage, and pharmaceutical industries to assure safe process water.

Laboratories, governmental authorities, and water utilities benefit from the method’s flexibility, statistical reliability, and direct applicability to various water matrices. Its ability to handle samples with high turbidity or background flora makes it especially valuable for challenging environmental samples.

Related Standards

To ensure comprehensive water quality assessment and regulatory conformance, refer also to:

• ISO 8199: General guide to the enumeration of microorganisms by culture.
• ISO 19458: Procedures for sampling water for microbiological analysis.
• EN ISO 9308-1: Membrane filtration method for waters with low background flora (complementary to part 2).
• EN ISO 5667 Series: Guidelines for water sampling.
• Drinking Water Directives (EU, WHO, National Regulations): Standards for microbiological parameters in drinking water.

These related standards provide essential background for designing sampling protocols, confirming laboratory competence, and selecting suitable testing methodologies for comprehensive water microbiology assessment.

By implementing SIST EN ISO 9308-2:2014, organizations can ensure reliable, sensitive detection of E. coli and coliform bacteria-key indicators of water quality and safety-across a diverse range of water sources and monitoring needs.