Take the Tummy Trouble Quiz Digestive Disease Myths Slideshow Pictures Heartburn? Foods to Eat, Foods to Avoid Slideshow

Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

View Full Profile

Medical Editor:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

View Full Profile

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 160F 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).

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.

What are the symptoms caused by enterovirulent E. coli (EEC)?

The major symptom that all enterovirulent E. coli (EEC) produce in common is diarrhea. However, the type of diarrhea (for example, bloody, chronic, or self-limiting) and the complications that may accompany the infections differ from each other. Similarities of symptoms have caused researchers and clinicians to arrange E. coli serotypes into groups according to their symptoms and common pathogenic mechanisms. Depending on which research or clinical physicians publications are read, there are 4 to 6 groups of E. coli that comprise all of the enterovirulent E. coli (EEC). Unfortunately, some investigators have more than one term for some members of the groups. The following is a summary of the groups that are currently in the literature and the symptoms group members cause:

• EHEC (enterohemorrhagic E. coli): bloody diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP); additional terms for EHEC are VTEC and STEC which stand for Vero toxin-producing E. coli and Shiga toxin-producing E. coli, respectively. One serotype, E. coli 0157:H7, is responsible for the majority of the bloody diarrhea that occurs due to the production of Shiga toxins.
  
  
• ETEC (enterotoxigenic E. coli): traveler's diarrhea, a watery diarrhea with nausea, abdominal cramping, and fever, caused by several serotypes of E. coli (0169:H47, 0148:H28 and several others) that produce two toxins that cause the gastrointestinal tract to secrete fluid (secretory exotoxins)
  
  
• EPEC (enteropathogenic E. coli): childhood diarrhea, caused by E. coli bacteria (many different serotypes) that can attach to gastrointestinal tissues, especially in infants, and produces a watery or bloody diarrhea in infants by producing a toxin similar to that produced by the bacterium named Shigella dysenteriae.
  
  
• EIEC (enteroinvasive E. coli): Shigella-like dysentery with blood and mucus, due to E. coli that invade epithelial cells of people of all ages, also producing vomiting, fever and chills. These serotypes are closely related to Shigella spp. (a few children develop HUS)
  
  
• EAEC (enteroadherent E. coli): childhood watery diarrhea, some cases of traveler's diarrhea in adults, and some urinary tract infections. This group is composed of E. coli strains (for example, 0119 or 055) that are able to adhere to human cells (gastrointestinal and other cell types). About one-half of this group are able to cause mild diarrhea, usually in children, while other E. coli serotypes that can adhere, do not cause any disease. Like EAggEC, these enteroadherent E. coli do not produce any Shiga toxins or secretory-causing exotoxins.
  
  
• EAggEC (enteroaggregative E. coli): persistent diarrhea in developing countries especially in children that usually lasts more than 14 days. The diarrhea is watery, mucus-containing, and in about one-third of individuals, bloody. Those with EAggEC usually have only a low fever (less than 101 F or 38.3 C) and almost no vomiting. These E. coli serotypes (for example, 042 and 044) do not produce any Shiga toxins or secretory exotoxins that cause secretions but cause intestinal inflammation that is linked to abnormally high intestinal secretion that leads to watery diarrhea. These strains are unique because they "aggregate" (form small masses comprised of cultured tissue cells and bacteria) human gastrointestinal cells by attaching via fimbriae (pili).

As one can surmise, there are unfortunate overlaps in disease syndromes and that is one reason that authors disagree on the actual number of groups (EPEC, EAEC, and EAggEC or EACE and EAggEC are often lumped together). It seems unlikely that the group names will remain stable in the future (see next section).