Why is escherichia coli considered an indicator of pollution

Escherichia coli abbreviated as E. Although most strains of E. Some kinds of E. Total coliforms are gram-negative, aerobic or faculative anaerobic, nonspore forming rods. These bacteria were originally believed to indicate the presence of fecal contamination, however total coliforms have been found to be widely distributed in nature and not always associated with the gastrointestinal tract of warm blooded animals.

The number of total coliform bacteria in the environment is still widely used as an indicator for potable water in the U. Fecal coliform bacteria are a subgroup of coliform bacteria that were used to establish the first microbial water quality criteria. The ability to grow at an elevated temperature Fecal- coliform bacteria are detected by counting the dark-blue to blue-grey colonies that grow on a 0.

The presence of fecal coliforms in water indicates that fecal contamination of the water by a warm-blooded animal has occurred, however, recent studies have found no statistical relationship between fecal coliform concentrations and swimmer-associated sickness. It is a member of the fecal coliform group of bacteria and is distinguished by its inability to break down urease.

The addition of urea substrate confirms that colonies are E. This bacteria is a preferred indicator for freshwater recreation and its presence provides direct evidence of fecal contamination from warm-blooded animals. Although usually harmless, E. A recently discovered strain of E. Consumption of or contact with water contaminated with feces of warm-blooded animals can cause a variety of illnesses.

Minor gastrointestinal discomfort is probably the most common symptom; however, pathogens that may cause only minor sickness in some people may cause serious conditions or death in others, especially in the very young, old, or those with weakened immunological systems.

What is in that water that you just drank? However, for routine monitoring of water quality this technology is not a viable alternative as it is more expensive, requires specialist equipment and trained analysts and does not provide rapid or onsite results.

The coupling of microarray technology with PCR enhances detection and identification of bacterial contaminants in water samples. Several commercial kits are now available for the assay of shiga toxin producing E.

More recently, detection techniques using biosensors have shown potential for onsite monitoring. These combine a rapid biochemical reaction with a physicochemical signal that is proportional to the concentration of the target molecule and thus the number of bacteria present in a sample. A system that combines concentration of E.

Several immunosensors have also been developed, mostly in order to detect specific bacterial antigens correlated with virulence. Capacitors can be utilised to detect whole cells and a recent paper describes a biosensor that can specifically detect E. Proteomics methods have been developed and extensive databases created allowing the identification of microorganisms directly in complex samples. A study by Loff [ 64 ] compares proteomics analysis with molecular and biochemical methods for the detection of microorganisms commonly associated with water safety.

It can be expected that future developments of this technology will widen its application in many diagnostic and analytical applications. It has to be noted that the identification of organisms and detection of virulence or resistance by both molecular and proteomics approaches relies on the comparison of results with existing databases.

This limits to the identification of known strains and characterised genes and proteins and is thus unlikely to achieve detection of uncultivable microorganisms. However, a combination of recent advances in bioinformatics and novel methods like the one described by Kaeberlein [ 65 ] have increased our knowledge about the microbial world and extended our database resources.

Molecular and proteomics methods have shown great potential in the identification in temporal and special distribution of microorganisms in the aquatic environment and to combine species identification with detection of virulence and drug resistance.

Future developments are likely to combine the best of both worlds to achieve robust assessment of water quality by quantifying indicator organisms to detect contamination and identify virulence and resistance markers to assess public health risks and inform stakeholders on the need and nature of required interventions.

Although historically total coliforms, faecal coliforms, Enterococci and E. Approximately 3. Major etiological agents including Giardia , Cryptosporidium , Vibrio cholerae and Salmonella would be missed by current testing procedures. Often outbreaks are due to local flood or storm events or releases of untreated sewage which result in significant contamination of environmental water.

Worldwide morbidity and mortality caused by contaminated drinking water is of considerable magnitude. The WHO ranks diarrhoeal diseases sixths highest in the list of causes of environmental deaths with an estimate of , deaths annually [ 68 ].

This highlights the need for a concentrated effort to make both recreational and drinking water safe in both developing and developed countries [ 4 ]. The development of methods detecting a wide range of significant pathogens is most likely to be achieved by extraction and antibody based detection, as described for pathogenic protozoa [ 69 ] or molecular techniques such as PCR, shown for Cryptosporidium parvum and Giardia lamblia [ 70 ], and with further developments of NGS and MALDI.

However, the advantage of the currently used E. Additional more broad ranging tests would need to be rigorously assessed in a wide variety of environmental situations before they could be adapted as international standards. Sensitive and frequent monitoring of environmental waters is essential to minimise adverse effect on human health. The current approach to monitoring for contamination in environmental waters is shown in Figure 1.

Current approach to monitoring and identifying bacteria in environmental water. The quantification of the indicator organisms E. A secondary objective of environmental monitoring is the identification and quantification of bacteria present in water samples and this is best achieved by molecular methods.

Whereas culture methods have the limitation of only providing information the day after collection of the sample, all the other methods currently available have some limitations as well when used for environmental samples. In the case of molecular methods this is the need to concentrate the sample or amplify the DNA, further the highly specific target sequences that are used could result in an underestimation of the actual level of indicator organism.

The most promising area is the development of a wide range of biosensor systems which show promising simplicity for direct and in situ analysis. Licensee IntechOpen.

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Downloaded: Abstract Good public health depends on regular monitoring of water quality as faecal contamination is a serious problem due to the potential for contracting disease. Keywords water quality monitoring E. Introduction Pathogen contamination of environmental waters is a major health risk and a threat to future supplies of water for living and recreational activities. Detects primary indicator organism and others present, relies on biochemical or immunological methods of identification, underestimates bacterial load as only viable organisms detected.

Escherichia coli, water quality, indicator, trends. How to Cite. Odonkor, S. Escherichia coli as an indicator of bacteriological quality of water: an overview. Microbiology Research , 4 1 , e2. Copyright c Stephen T. Odonkor, Joseph K. Most read articles by the same author s Stephen T. Odonkor, Mercy J.