Natural water supplies such as rivers, lakes, and streams contain sufficient nutrients to support growth of various organisms. Microorganisms enter the water supply in several different ways. In congested centers water supplies get polluted by domestic and industrial wastes. As a potential carrier of pathogenic microorganisms, water can endanger health and life.

Drinking water is obtained from different sources like well, river and surface waters. Various impurities, from branches of trees to invisible microorganisms, may occur in these waters and have to be removed before the water is supplied to the public. To render the water safe for drinking it has to be treated property.

A proper sampling is essential to provide representative samples to the laboratory in charge of conducting the tests. Sampling characteristics depend on the objective pursued as well as on the nature of the sample.

Culture media for Water analysis

Microorganisms are living organisms. In addition, when found in water, they are not a perfect solution, but a suspension with a degree of variability that is inherent to it. The presence and level of fecal contamination is an important factor in assessing the quality of water bodies and the risk of infection posed to human health.

The analysis of water samples to detect Escherichia coli, which normally inhabits the intestinal tract of humans and other warm-blooded animals, provides an indication of this type of contamination.

Other indicators of fecal contamination are Enterococci. Such microorganisms are particularly important when the contamination occurred some time ago and less resistant coliform bacteria, including Escherichia coli, may have died when the analysis is performed.

Pseudomonas aeruginosa is an opportunistic pathogen for humans that is capable of growing in water with very low nutrient concentrations. It is desirable that natural mineral waters, spring waters, bottled waters and waters for human consumption are exempt from Pseudomonas aeruginosa. Sometimes, for reasons of public health, presence of Pseudomonas in other types of water may be investigated, including water in swimming pools.

For the identification of all these pathogens of importance in the analysis of water, there are specific culture media:

Waters in general:

  • R2A Agar: Recommended by the European Pharmacopoeia for total aerobe count in treated water

Enterococci:

Coliforms:

Pseudomonas aeruginosa:

Other microorganisms: