Escherichia coli (E. coli) are normal bacteria of the human gastrointestinal tract. Most E. coli are harmless and are an important part of a healthy human digestive system1. However, some E. coli strains acquire additional genetic material and become pathogenic. E. coli diarrheal illness is among the most frequent bacterial causes of gastroenteritis worldwide2.
There are six pathogenic strains of E. coli that are associated with diarrhea. These six strains are enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), diffusely adherent E. coli (DAEC), and Shiga toxin-producing E. coli (STEC) that is also referred to as Verocytotoxin-producing E. coli (VTEC) or enterohemorrhagic E. coli (EHEC). STEC is the one most commonly heard about in the news in association with foodborne outbreaks. The most common identified STEC in North America is E. coli O157:H71.
An estimated 265,000 STEC infections occur each year in the United States. In 2018, there was a large outbreak of STEC (E. coli O157:H7) linked to romaine lettuce from a growing region in Yuma, Arizona. The outbreak affected 210 people in 36 states and caused five deaths. Just recently, as of November 22nd, 2019, there was an outbreak of STEC (E. coli O157:H7) linked to romaine lettuce harvested from the Salinas, California growing region with a reported 40 cases in 16 states so far1.
The most common way to acquire an E. coli infection is by eating contaminated food, such as ground beef, unpasteurized milk, or fresh produce. Human and animal feces can pollute ground and surface water causing an infection as well. E. coli can also be transmitted from person-to-person contact with infected adults or children who do not wash their hands properly1.
Symptoms of STEC vary for each person but can include diarrhea (often bloody), vomiting, and severe stomach cramps. Some people can even develop a fever. Most people start to feel sick 3 to 4 days after eating or drinking something that contains the bacteria. However, symptoms can start anywhere from 1 to 10 days after exposure. People at risk for acquiring a foodborne illness are pregnant women, newborns, children, older adults, and those with weakened immune systems such as those with cancer, diabetes, or HIV/AIDS1.
About 5 to 10% of people who are diagnosed with STEC can develop a potentially life-threatening complication known as hemolytic uremic syndrome (HUS). HUS develops about 7 days after symptoms first start to appear. Signs of HUS include decreased frequency of urination, fatigue, and losing color in your cheeks or inside the lower eyelids. People should be hospitalized since HUS can cause damage to the kidneys. Most people recover within a few weeks, but some suffer permanent damage or even die from HUS1.
Treatment for pathogenic E. coli infections ranges from adequate hydration to antibiotics. However, antibiotics are not routinely recommended since most cases of diarrhea resolve spontaneously and antibiotics are to be avoided for STEC infections since there is an increased risk of HUS. Antibiotics are reasonable in patients with severe symptoms such as a fever, more than six stools a day, prolonged diarrhea (> 7 days), and in people who are severely dehydrated requiring hospitalization2.
Prevention of E. coli includes avoiding raw, unpasteurized dairy products and juices; not swallowing water when swimming and when playing in lakes, ponds, streams, or swimming pools; cooking meats thoroughly; washing fruits and vegetables well under running water; and washing your hands thoroughly after using the bathroom and changing diapers along with before and after preparing or eating food1.