Clostridium perfringens

(endorsed 2011)

Guideline

No guideline value has been set for Clostridium perfringens in drinking water. If used as an indicator and detected in drinking water, immediate action should be taken, including investigation of potential sources of faecal contamination.

General description

Clostridium spp. are anaerobic, sulfite-reducing, spore-forming bacilli. There are a number of species, of which C. perfringens is uniquely of faecal origin. Largely because it is anaerobic, C. perfringens rarely multiplies in water environments.

The spores are smaller than protozoan cysts and oocysts. They are exceptionally resistant to unfavourable conditions in water environments, including temperature and pH extremes, and are also resistant to disinfection processes such as chlorination.

Source and occurrence

C. perfringens is a member of the normal intestinal flora of 13-35% of humans, and is relatively common in dogs but less so in other warm-blooded animals (Leeming et al. 1998). The numbers excreted in faeces are normally substantially lower than those of Escherichia coli. C. perfringens and its spores are commonly present in sewage.

Method of identification and detection

There are standard methods for the detection and enumeration of C. perfringens using membrane filtration and multiple tube dilution methods (AS/NZS 4276.17.1 2000, AS/NZS 4276.17.2 2000). The assays involve incubation in selective media under anaerobic conditions. While assays for C. perfringens are more complicated than assays for other bacterial indicators such as E. coli or heterotrophic plate counts, they can be undertaken by standard microbiology laboratories.

Indicator value and application

Due to their small size and exceptional resistance to disinfection processes and other unfavourable environmental conditions, C. perfringens spores have been proposed as potential indicators for enteric viruses and protozoa in drinking-water supplies (Payment and Franco 1993). However, usefulness in routine monitoring of source water quality is limited by the fact that concentrations in faeces and sewage are far lower than E. coli. In addition, the survival of C. perfringens is much longer than that of enteric viruses and protozoa; hence detection in treated drinking water needs to be treated with caution, as the spores could be present long after faecal pollution and after death of other enteric pathogens (WHO 2004).

Monitoring of C. perfringens in drinking water could be undertaken to assess the likelihood of intermittent faecal contamination in distribution systems. If C. perfringens is detected, potential sources of contamination should be immediately investigated.

C. perfringens could be a useful indicator for validating removal of protozoa by filtration (WHO 2004).

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NOTE: Important general information is contained in PART II, Chapter 5

References

AS/NZS 4276.17.1 (2000). Water Microbiology Method 17.1: Spores of sulfite-reducing anaerobes (clostridia) including Clostridium perfringens – Membrane filtration method. Standards Australia, Standards New Zealand.

AS/NZS 4276.17.2 (2000). Water Microbiology Method 17.2: Spores of sulfite-reducing anaerobes (clostridia) including Clostridium perfringens – Estimation of most probable number (MPN) using the multiple tube dilution technique. Standards Australia, Standards New Zealand.

Leeming R, Nichols PD, Ashbolt NJ (1998). Distinguishing sources of faecal pollution in Australian inland and coastal waters using sterol biomarkers and microbial faecal indicators. Research Report 204, Water Services Association of Australia.

Payment P, Franco E (1993). Clostridium perfringens and somatic coliphages as indicators of the efficiency of drinking-water treatment for viruses and protozoan cysts. Applied and Environmental Microbiology, 59:2418-2424.

WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality, Section 11.6.5, Clostridium perfringens. Geneva: World Health Organization.