Enterovirulent E. coli (EEC) facts
- Enterovirulent E. coli (EEC) are bacteria that comprise several groups of E. coli serovars, all of which may cause diarrhea and other problems in the intestines.
- EEC bacteria can cause a wide range of symptoms ranging from mild to bloody diarrhea, nausea, vomiting, stomach cramping and dehydration. Different groups often produce less (EAEC group) or more intense symptoms (EHEC group) and complications.
- Although investigators vary on the group structure and names, six groups are currently presented in the medical literature, listed by their main symptoms produced or other "unique" group feature:
- EHEC (enterohemorrhagic E. coli): Shiga toxins; bloody diarrhea, 10% with complications
- ETEC (enterotoxigenic E. coli): secretory toxins; watery diarrhea
- EPEC (enteropathogenic E. coli): toxin similar to Shigella toxin; watery or bloody diarrhea
- EIEC (enteroinvasive E. coli): invade epithelial cells; mucoid, bloody diarrhea and fever
- EAEC (enteroadherent E. coli): adhere to intestinal cells; watery diarrhea
- EAggEC (enteroaggregative E. coli): clump intestinal cells; chronic mucoid watery diarrhea
- Dehydration may occur in any EEC group infection; if any signs of dehydration occur, seek medical care. Also seek care if bloody diarrhea develops.
- EEC infections are often presumptively diagnosed by association with a food, fluid or person that has been definitively diagnosed or associated with EEC contamination. Definitive diagnosis is made by isolating the EEC organism from feces of the patient and identifying the EEC group member by its toxin production, its unique group properties and its serotype.
- The majority of EEC group infections are self-limited; however, preventing dehydration is the major treatment for all EEC groups.
- Self-care at home can be done unless signs of dehydration or bloody diarrhea develop.
- The main complication that leads to other serious problems or death is dehydration. Serious complications are seen with EHEC group (mainly E. coli 0157:H7) occur more frequently than with the other groups; however, a high death rate (some report 50%) may occur in third-world countries with ETEC group infections.
- About 10% of EHEC infections (mainly E. coli 0157:H7) develop moderate to severe complications of bloody diarrhea, hemorrhagic colitis, hemolytic-uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP).
- Prevention of EEC centers on avoiding foods, fluids and touching persons with EEC. Cooking meats (especially hamburger meat) and other foods above 160 F (71.11 C) help kill the organisms. Food handlers should always keep food preparation items clean and their hands washed.
What are enterovirulent E. coli (EEC)?
Enterovirulent Escherichia coli (E. coli) are comprised of a number of serotypes (strains of related bacteria identified by their slightly different antigenic structures) of bacteria that have a strong propensity to cause infections, initially in the gastrointestinal tract ("entero" in Greek means intestine; virulent means deadly or disease-causing). Enterovirulent Escherichia coli (EEC) are members of the bacterial genus Escherichia, named after T. Escherich, who first isolated the bacteria in 1885. The majority of the genus Escherichia is composed of one species termed "coli" (Latin for colon); however there are over 700 serotypes of this bacterial species. Many E. coli serotypes may cause infections other than in the intestine, but the focus of this article is on the enterovirulent groups (EEC groups), with symptoms of the disease primarily limited to the fastrointestinal tract.
Escherichia coli (E. coli) are gram-negative bacteria that are rod-shaped, have the ability to survive in aerobic and anaerobic environments (termed a facultative anaerobe), and may or may not produce flagella and pili (thin hair-like projections) depending on environmental needs.
E. coli strains are found worldwide and live in significant numbers in humans and other animals as part of the normal bacterial population found in their large intestines. The organisms have likely co-existed with humans for eons in the normal flora (bacterial populations usually found in healthy individuals) of human and other animal colons. However, among the 700 strains of E. coli, there are a few strains that cause disease. These E. coli strains are some of the most frequent causes of many common bacterial infections, including diarrhea, cholecystitis, bacteremia, cholangitis, urinary tract infection (UTI), traveler's diarrhea, and other clinical infections such as neonatal meningitis, pneumonia, abdominal abscesses, and hemolytic uremic syndrome (HUS).
A classic example of such an E. coli strain is E. coli 0157:H7. The name E. coli 0157:H7 seems complex; however scientists use the numbers and letters to specifically designate small differences in E. coli strains. The 0157 is the "O" serotype antigen that identifies one of the over 700 strains and the "H" of H7 represents the antigen type on the bacterium's flagella. Some E. coli also possess K antigens (protein/polysaccharide surface components) that have been used to identify certain strains. These designations (O, H, and K) may be used to identify strains causing specific diseases and have been utilized to identify outbreaks of disease.