What it is:

• Escherichia coli, or E. coli, is a type of bacterium which includes hundreds of strains. It is a fecal coliform bacteria, found naturally in the intestines of humans and animals. It is named after its discoverer, Theodor Escherich, a 19th-century German physician.
• E. coli will grow in a wide variety of intestinal conditions.
• A typical rod-shaped E. coli cell measures about 2 microns by 0.5 microns.

Occurrence:

• Presence is a strong indicator of recent contamination by human sewage or animal feces. U.S. drinking water occasionally tests positive for total coliform bacteria, but seldom for E. coli being present. When found they are often present due to a cross connection with contaminated water or a backflow problem.
• Found from wastewater discharges or in agricultural runoff, surface water or groundwater.
• Most E. coli strains are harmless, but a few cause serious disease. Harmful strains include O157:H7, O121 and O104:H21.
• Humans can ingest E. coli by eating insufficiently cooked ground beef, hamburger or salami; eating unwashed, contaminated fresh vegetables; drinking unpasteurized milk or juice; or swimming in or drinking sewage or animal contaminated water.

Health effects:

• E. coli infection produces everything from no symptoms to bloody diarrhea, abdominal cramps, nausea and vomiting. Most people recover without treatment within 10 days. Some E. coli strains also can cause urinary tract infections and neonatal meningitis.
• In young children, the elderly and the immunocompromised, E. coli 0157:H7 can cause a life-threatening condition called hemolytic uremic syndrome, which destroys red blood cells and causes kidney failure.

Regulation:

• The U.S. Environmental Protection Agency (EPA) requires regular testing by public water systems for total coliform bacteria under the total coliform Rule. Monthly testing frequency for Total Coliforms is determined by system size and is from 1 per month to well over 400 per month. The maximum contaminant level (MCL) for total coliforms is zero per 100 ml, but up to 5 percent positive samples are permitted. If more than 5 percent of a system’s samples taken each month detect coliforms the system would be out of compliance. However, every positive coliform sample must immediately be tested for E. coli or fecal coliforms. The test requires a UV lamp and it requires only a few seconds. The system must continue testing in and near the same location where the positive total coliform sample was obtained and take corrective actions if the contamination has persisted. The fecal or E. coli specification is 0 per 100 ml. If detected the water supplier must take immediate corrective action. Detection of E. coli in this process creates a “direct health risk.” The rule does not apply to private wells (EPA recommends regular testing).

Water treatment:

• E. coli are highly susceptible to chlorine disinfection. Surface waters are usually filtered before disinfection to remove turbidity and improve the effectiveness of disinfection process. Other disinfectants and more expensive technologies also work but they are not necessary to eliminate E. coli.

Sources: Centers for Disease Control and Prevention (CDC), U.S. Environmental Protection Agency (EPA), WebMD^®.