Revised ISO 17995 Water Quality

The thermotolerant Campylobacter species are not thought to propagate as free living but are zoonotic pathogenic bacteria of mammals and birds and which cause disease in humans. The vehicles for Campylobacter infections are usually food, farm animals, pets and person‑to‑person contact; water is also important. They can be isolated from waters contaminated with human or animal faeces such as wastewater and surface waters. The bacteria have been demonstrated to survive within amoebae. Outbreaks of campylobacteriosis have been reported in relation to the use of contaminated drinking water and sporadic cases from recreational water use.

This second edition of ISO 17995 has been technically revised by the Technical Committee ISO/TC 147, Water quality, Subcommittee SC 4, Microbiological methods, and cancels and replaces the first edition (ISO 17995:2005).

Scope of the revised method

It specifies a method for the detection, semi-quantitative and quantitative (MPN) enumeration of thermotolerant Campylobacter species.

The method can be applied to all kinds of waters including: drinking water, ground water and well water, fresh, brackish and saline surface water, swimming pools, spa and hydrotherapy pools, recreational waters, agricultural waters and runoff, untreated and treated wastewater and also sand and other sediments.

This method can be used for the detection of Campylobacter species in a specified sample volume. Clean water samples with low turbidity can be membrane filtered for either a qualitative method, semi-quantitative or quantitative (MPN) method. Water samples with higher turbidity, such as primary and secondary wastewater effluents and sediments, are analysed using the same qualitative, semi-quantitative or quantitative MPN method by direct inoculation of material into bottles or tubes. Sediments can be suspended in a suitable diluent or inoculated directly into enrichment broths.

Those wishing to use this method are expected to verify its performance for the particular matrix under their own laboratory conditions.

Principle of the revised method

Samples are inoculated either directly or after concentration using membrane filtration into one of two selective enrichment broths depending on the expected level of background microorganisms: Bolton broth for clean water and Preston broth for more heavily contaminated water.

From the enrichment broth cultures, liquid selective media are inoculated onto modified charcoal cefoperazone deoxycholate agar (mCCDA). Confirmation of suspect colonies of Campylobacter species involves biochemical, morphological and physiological tests.
If typical Campylobacter species are confirmed or identified, the result is given as the qualitative, semi‑quantitative or quantitative (MPN) estimate per volume of sample.

2019 main changes of the revised ISO 17995

The main changes compared to the previous edition (ISO 17995:2005) are as follows:

• the inclusion of direct inoculation of enrichment broths in addition to membrane filtration with additional information about sample processing.
• methods for the speciation of Campylobacter.
• performance testing for the quality assurance of culture media has been added to Annex D.
• performance characteristics of the method have been added as an Annex E.