Table of Contents
Background
E. coli and total coliforms include bacterial types that can be found in the environment, particularly in water sources. Among these, E. coli belongs to a specific type of fecal coliform bacteria which is found in the feces of warm-blooded animals including human beings, and is often used as an indicator of fecal pollution in water sources. On the other hand, total coliforms refer to a broader bacterial category including E.coli and various other coliform bacterial strains commonly found in the environment. Both E. coli and total coliforms possess the potential of causing illness if consumed in large quantities. They can be found in drinking water through various sources including the fecal matter of warm-blooded animals and humans, agricultural runoff containing animal farming residues and fertilizers which can introduce E. Coli and total coliforms into the water sources, poorly or improperly treated sewage, improperly treated drinking water, land use changes, improper waste disposal, leakage or overflow from septic tanks, and leakage from the water supply network.
Further, wildlife and stormwater can also be the possible source of ground and surface water contamination from bacteria. Importantly, E. coli and total coliform presence in drinking water do not necessarily refer to being unsafe since many strains of E.coli are not harmful to humans. However, their presence may indicate contamination in drinking water with the necessity of being tested. Therefore, drinking water should regularly be monitored for these bacteria and any contamination should be addressed immediately to ensure a safe drinking water supply to the consumers. Moreover, the drinking water regulations and prescribed standards may vary depending on the country and region, so it is important to check with local authorities for specific guidelines to monitor bacteria in drinking water. In the US, the Safe Drinking Water Act (SDWA) regulates the presence of E. coli and total coliforms in public drinking water systems.
To ensure that, EPA has set the MCL for E. coli at zero, and for total coliforms, it should be less than or equal to 5% of samples total coliform-positive per month. This means that safe drinking water should be free of any contamination from E. coli and total coliforms in all public drinking water systems. EPA regulations also require regular monitoring of these bacteria through suitable testing and demands necessary actions if their presence is detected in drinking water. If E. coli is detected in a public water system, the system must notify its customers immediately, and take steps to correct the problem and restore safe drinking water. If total coliform is detected, the system must take additional samples to determine if fecal coliform or E. coli are also present. If fecal coliform or E. coli are present, the system must notify its customers and take steps to correct the problem.
If a public water system repeatedly fails to meet the MCL for E. coli or total coliform, the EPA or the state may take enforcement action, which can include fines or penalties. In NYC and NJ, the presence of E. coli and total coliforms in drinking water is enforced and monitored by the EPA and State departments of Environmental Protection (DEP). Once ingested, the E. coli-contaminated drinking water can result in many health problems including diarrhea, abdominal cramps, nausea, vomiting, and dehydration. Their severe impacts may lead to kidney failure and even death. The general symptoms appear within 2-5 days of exposure which may last up to a week. The presence of bacteria in drinking water systems can also have negative economic impacts along with damaging the repute of water suppliers leading to mistrust among consumers. Susceptibility to disease associated with bacterial infections through drinking water varies among individuals based on their age group (infants > young children > pregnant women > elderly), and immune systems. Therefore, regular monitoring of drinking water supplies for E. coli and total coliforms is warranted to ensure that the consumers are receiving contaminant-free drinking water.
E. coli and total coliforms, when consumed through drinking water may potentially result in various illnesses among humans through various disease mechanisms and pathways. They can survive and grow in the human gut resulting in forming colonies in the intestinal tract and disrupting the normal balance of gut microbiota leading to illness (Edberg et al. 2000; Strauss et al. 2001). Infectious strains of E. coli produce toxins called Shiga-like toxins having the potential to damage intestinal linings leading to symptoms such as diarrhea and abdominal cramps (Lascowski et al. 2013; Lim et al. 2020).
The mechanism of these toxins involves the binding of toxins to the cell’s surface in the gut which causes the release of inflammatory mediators leading to inflammation and intestinal lining damage (Vimont et al. 2012). Their metabolism is mainly dependent on the type of bacterial strain and the health of individuals exposed to these bacteria. It has been reported that some strains of E. coli and total coliform are associated with infections and disease progression while other may not pose any serious health concerns. Under serious infection conditions, E. coli can result in serious complications including renal failure and anemia. Some other body organs and parts have also been reported to be infected with these bacteria such as urinary tract and wound infections (Kudinha 2017).
It is important to mention that some E. coli strains also produce specific adhesins called FimH, allowing bacteria to bind to the cells lining in the gut resulting in the formation of colonies having an increased risk of infection (Tseng et al. 2020). On the other hand, the total coliforms can produce toxins including heat-stable toxins, enterotoxins, and cytotoxins that may result in severe diarrhea and other symptoms (Gemeda et al. 2022). These toxins can cause damage to epithelial cells in the gut and disrupt the electrolyte balance in the human gut. Moreover, E. coli is also reported to activate the host’s immune response leading to the production of inflammatory mediators like IL-1, IL-8, and TNF-alpha, which can contribute to gut inflammation and damage (Bannerman et al. 2004)
Detection Methods and Removal Strategies
Detection of E. coli and total coliforms in drinking water can be done through many methods. Among widely used methods include 1) membrane filtration (MF) which involves a special membrane through which the water sample is filtered followed by incubation of the membrane on a growth medium selective for E. coli or total coliforms. Any strain of these bacteria in the water sample can be easily detected by observing the colonial growth on the membrane (Dunling and Fiessel 2008). 2) Multiple tube fermentation (MTF) in which a water sample is added to multiple tubes containing selective growth medium for E. coli and total coliforms.
The presence of these bacteria can be confirmed by observing gas bubbles production due to the growth of E. coli and total coliforms in the tubes (Nikaeen et al. 2009). 3) Enzyme substrate method (ES) which uses an enzyme substrate that will result in color change in the presence of E. coli and total coliforms (Olstadt et al. 2007). 4) Polymerase chain reaction (PCR) method can detect E. coli and total coliforms through the amplification of specific DNA of these bacteria. The method is very sensitive with the capability of detecting very low levels of bacteria in drinking water samples (Isfahani et al. 2017). 5) Immunological methods make use of specific antibodies to detect E. coli and total coliforms in drinking water. The method is very rapid and can provide results within a few hours (Gunda et al. 2014). Every method has its advantages and disadvantages. Therefore preference for detection method mainly relies on the desired results, availability of technology, and operating costs.
Detected strains of E. coli and total coliforms can be removed from drinking water using various methods. Some widely used methods for their removal include chlorination which involves the addition of chlorine to the water that results in killing the bacteria by disrupting their cell walls (Ma et al. 2022). Ultraviolet disinfection (UV) is also a very common and effective method for bacterial removal from drinking water by passing UV light through the water sample (Rezaee et al. 2011). Ozonation is another effective technique to remove E. coli and total coliforms which uses ozone gas to disinfect water by destroying the bacterial cell walls because of the powerful oxidizing property of ozone (Karnik et al. 2007). Specially designed filters are now available for microbial removal and can effectively remove E. coli and coliforms.
Other methods include reverse osmosis (RO) which can remove E. coli and total coliform after passing water from a semipermeable membrane with pressure. Boiling drinking water for about one minute is also a very effective method of killing most bacterial types of bacteria including E. coli and total coliform. This method can easily be used at the domestic level by consumers to avoid any bacterial contamination in their drinking water. It is important to note that more than one method may be needed for effective bacterial removal based on the severity of contamination.
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC and NJ region.
The MCL for bacteria in drinking water is zero total coliform colonies per 100 milliliters of water as established by the EPA. The total coliform test is the basic yardstick for determining the biological quality of a water supply.
Escherichia coli (E. coli) is the major species in the fecal coliform group found in drinking water. Of the five general groups of bacteria that comprise the total coliforms, only E. coli is generally not found growing and reproducing in the environment.
When a water test indicates a high “Total Coliform” count, the water may or may not contain illness-causing strains such as E. coli. But, when present, coliform is a strong indicator that your water source has already been or can easily become contaminated with fecal matter, and you should disinfect your water.
The Total Coliform Rule (TCR) is the Federal regulation under the Safe Drinking Water Act (SDWA) that sets MCLs and monitoring requirements for certain biological contaminants. It requires. every PWS to periodically collect samples and analyze them for bacteria.
If total coliform is present in water, the lab also tests the sample for E. coli. Total coliform bacteria are common in the environment (soil or vegetation) and are generally harmless.
Contaminants such as coliform bacteria are most effectively eliminated through chlorine disinfection, filtration, ultraviolet irradiation, and ozonation.
The best approach to kill E. coli in drinking water suggests boiling your water for 1 minute or disinfecting it using chemicals. Specially designed filters and other water treatment technologies might also be effective.
Symptoms include diarrhea, stomach cramps, and occasionally fever. About half of the people with the infection will have bloody diarrhea. People usually notice symptoms 3 to 4 days after they have been infected. But symptoms can start any time between 1 and 14 days afterward.
E.coli can survive in river/surface water for 27 days and in cattle slurry for 10 days. On stainless steel, E. coli has been shown to survive for more than 60 days.
E. coli numbers in freshwater are determined by counting the number of yellow and yellow-brown colonies growing on a 0.45-micron filter placed on m-TEC media and incubated at 35.0º C for 22-24 hours. The addition of urea substrate confirms that colonies are E. coli.
Conclusion
E. coli and total coliform contamination in drinking water refer to the contamination associated with fecal sources. Various sources have been identified to contaminate drinking water with these bacteria. The presence of E. coli and total coliform in drinking water is regulated by EPA which has set MCL for these bacteria. Their presence in drinking water is associated with various health issues and therefore regular monitoring of drinking water must be ensured to prevent public health from bacterial contamination in the US.
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- Yasir A. Rehman, Ph.D.
Dr. Rehman was born in Rawalpindi, Pakistan. He completed his MSc from PMAS – Arid Agriculture University Rawalpindi in 2011 where his thesis comprised a health risk assessment of subjects living in the vicinity of wastewater channels in urban settings and its relationship with the incidence of Malaria.
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OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
