Day 14: E. Coli

While there are many strains of E. Coli that do not cause diarrheal disease, it is a species of bacteria that is used as an indicator of fecal contamination of drinking water.  There are many different microorganisms that can cause sickness and death when consumed in drinking water, however because they are so diverse and each require different testing methods, E. Coli has emerged as a global standard for determining whether any such organisms may be present.  Some strains of E. Coli are highly pathogenic, and can result in sickness, diarrhea and death.  Current EPA & WHO guidelines require that even a single live bacteria (often called a colony forming unit, or CFU) in a 100/mL sample must be boiled or disinfected.

E. Coli was first discovered in 1887 when a German pediatrician, Theodor Escherich, found it growing in the feces of healthy individuals.  Because this species was found to thrive at human body temperature, it was classified as a thermotolerant bacteria – one that could be cultured from a sample at temperatures that kill off other species present.  Because it can also be grown much faster and much more easily than other species in a laboratory setting, it became one of the fastest and most reliable analytical methods for assessing the potability of water.  Because treatment protocols for limiting E. Coli levels are not in-of-themselves adequate for removing all microbiological contaminants, in recent years, the use of E. Coli as an indicator organism has fallen under criticism.  To some degree, strains of protozoa, parasites and viruses that exhibit resistance to standardized treatment methods have become a greater problem because of the focus on E. Coli, yet until a more effective standard is developed, it is likely to remain the first and most common test performed in assessing drinking water quality.

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