Microbiological Testing
Indicator Bacteria
The potential for water-borne disease arises when water is polluted with faecal matter. Polluted water may contain pathogenic faecal bacteria, viruses, or other micro-organisms. It would be far too complex to try and detect all of these on a routine basis. It is therefore normal practice to look for "indicator bacteria". These are bacteria that are always excreted in large numbers in the faeces of humans and other animals, whether they are healthy or sick. Their presence indicates faecal contamination; it does not prove that water-borne disease is occurring.
Faecal Coliforms, which include Escherichia coli, are a subgroup of the total coliform group and they occur almost entirely in faeces. By contrast, other members of the coliform group can be free-living in nature and therefore their presence in water is not necessarily evidence of faecal contamination. Escherichia coli are always present in faeces, the majority of which are not pathogenic.
Enterococci, are another group of indicator bacteria. They also are faecal in origin, and while not as specific or as abundant in faecal material as faecal coliforms, they are more persistent in water than E. coli, and so may be a better indicator of the presence of certain pathogens that die off slowly (e.g. viruses).
Testing
| Test | Type of Sample |
| Total Coliforms | Drinking Water, Swimming Pools |
| Faecal Coliforms | Drinking Water, Swimming Pools, Streams, Rivers, Lakes, Dams, Outfalls |
| E. coli | Drinking Water, Swimming Pools, Streams, Rivers, Lakes, Dams, Outfalls, Oysters, Prawns |
| Enterococci | Streams, Rivers, Estuarine waters |
| Pseudomonas aeruginosa | Swimming Pools, Drinking Water |
| Total Plate Count | Drinking water, Miscellaneous |