What it is:
• Escherichia coli, or E. coli, is a type of bacterium which includes hundreds of strains. It is a type of 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.

• Presence is a strong indicator of recent contamination by human sewage or animal feces. Water can test positive for coliform bacteria without E. coli being present.
• Found 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-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: hemolytic uremic syndrome, which destroys red blood cells and causes kidney failure.

In the news:
• Illness-causing E. coli in ground beef and spinach sold in supermarkets or restaurants has been in the news recently. One major O157:H7 outbreak was due to contaminated groundwater: In 1999 at the Washington County Fair in upstate New York, a well at the fair used for drinking and food preparation was contaminated by manure from a nearby animal barn. The result was two deaths, 65 people hospitalized and more than 1,000 sickened.

• U.S. Environmental Protection Agency (EPA) requires regular testing by public water systems for coliform bacteria under the Total Coliform Rule. The maximum contaminant level (MCL) goal for total coliforms is zero. If more than 5 percent of a system’s samples taken each month detect coliforms, this must be reported to the public, the system must continue testing, and it may need to take immediate corrective action. Detection of E. coli in this process creates a “direct health risk.” Testing frequency is determined by system size. Rule does not apply to private wells (EPA recommends regular testing).

Water treatment:
• Highly effective at E. coli removal: ultrafiltration, nanofiltration, reverse osmosis, distillation, ultraviolet, chlorination, ozone, boiling.

Sources: EPA, US Centers for Disease Control and Prevention, WebMD®.