| Escherichia coli (E. coli) is a common type of bacteria with hundreds of strains. Typically harmless, most strains produce infection only under special circumstances, such as when they are introduced into a body site that is normally sterile. In general, E. coli causes an inflammation of the small intestine, which in adults is self-limiting but in children can have dire consequences, possibly even resulting in death. In other cases, depending on the body site entered, E. coli can produce a variety of infections, ranging from a routine infection of the urinary tract to a life-threatening infection of the blood (septicemia).
A number of E. coli strains are routinely harmful. They produce a mild to severe and sometimes fatal foodborne intestinal infection. Although E. coli is the most common type of bacteria in the intestine, when harmful strains gain entrance they damage the intestinal wall, either by releasing a toxin or by actually penetrating and invading the wall. The result is an intestinal infection (gastroenteritis) that causes diarrhea.
Six categories of E. coli produce diarrheal gastroenteritis. Three of them affect adults: enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), and enteroinvasive E. coli (EIEC). Within each of these categories, there are a variety of E. coli strains.
EHEC is the one most often mentioned in the media today. It is referred to as E. coli O157:H7, although it is only one of a number of strains within this category. The toxin released by EHEC produces a type of bloody diarrhea known as hemorrhagic colitis. Serious and even fatal complications can also develop. EHEC originates in animals, particularly cattle and sometimes deer, and can be passed to individuals who consume undercooked meat (particularly ground beef), contaminated water, and raw milk. It can also be transmitted through apple cider, fruits, and vegetables contaminated with feces from infected animals or from other infected individuals.
ETEC commonly causes traveler's diarrhea. Like EHEC, ETEC produces symptoms through the release of a toxin. The bacteria are passed from individual to individual through food or water contaminated with the infected individual's feces.
EIEC causes a type of gastroenteritis known as bacillary dysentery. It is also passed from individual to individual through contaminated food or water. Unlike EHEC and ETEC, EIEC does not produce a toxin but rather invades the intestinal wall. It is primarily found in underdeveloped countries; only occasional cases have been reported in an industrialized country.Risk: Of all the various strains of E. coli, 0157:H7 has gained the widest attention in the US because of the much-publicized consequences from eating undercooked beef. Generally, the illness is mild and resolves in less than 10 days. But, mostly in children under 5 and the elderly, the disease may result in red blood cell destruction and kidney failure (hemolytic uremic syndrome, or HUS). This occurs in 2% to 7% of 0157:H7 infections. In the US, hemolytic uremic syndrome is the greatest cause of acute kidney failure in children, and most of these cases are caused by E. coli 0157:H7. Beef is not the only source of this strain; it is also found in any foods contaminated with feces, such as lettuce, vegetables, unpasteurized milk and juice, and in contaminated swimming or drinking water. The bacteria also spreads from infected persons when handwashing is not adequate. Incidence and Prevalence: EHEC diarrhea occurs in North America, Europe, South Africa, Japan, and the southern portions of South America and Australia. In the US, EHEC produces approximately 73,000 cases of infection and causes 61 deaths each year ("Escherichia Coli").
In adults, ETEC typically occurs when an individual from an industrialized country visits a developing country. Up to 60% of North American visitors to Mexico develop ETEC traveler's diarrhea. |
Source: Medical Disability Advisor
| History: Individuals with EHEC typically have bloody diarrhea and abdominal cramps but usually no fever. Sometimes an individual may report a mild fever. Symptoms begin 2 to 8 days after exposure to the bacteria and last 5 to 10 days.
Individuals with ETEC produce large quantities of watery diarrhea. Some individuals also report abdominal cramps, vomiting, and exhaustion. Symptoms begin 10 to 72 hours after exposure and last fewer than 5 days.
EIEC produces symptoms that include watery diarrhea, sometimes containing mucous, severe abdominal cramps, and fever. This diarrhea may become bloody. Physical exam: The skin, mouth, and lips appear dry due to dehydration. Rapid breathing, drowsiness, or confusion may indicate acidosis, a condition in which the acid-base balance is disturbed due to prolonged diarrhea. Although the cause must be confirmed with testing, bloody or watery diarrhea alerts the physician to a diagnosis of diarrheal intestinal infection (gastroenteritis). Bloody diarrhea plus signs of kidney (renal) involvement may suggest EHEC. Tests: EHEC may be grown and identified from a stool specimen with a special E. coli O157:H7 culture (not a routine bacterial stool culture). The organism may also be identified by a DNA probe test or by testing for the toxin it produces. Additional identifying information about the organism, such as might be needed when studying an outbreak, can be obtained from a serotyping test.
ETEC cannot be identified by a bacterial culture. It must be identified by a DNA probe test, a test for its toxin, or an immunoassay in which one of its proteins is detected.
EIEC also cannot be identified by bacterial culture. It is identified by a DNA probe test, an immunoassay in which one of its proteins is detected, or a bioassay in which its ability to invade tissue is detected. A clue to the presence of EIEC is the presence of white blood cells found during microscopic examination of a stool specimen. |
Source: Medical Disability Advisor
| EHEC is primarily treated with fluid and electrolyte replacement. Whether or not antibiotics should be used is still a matter of debate. There is evidence to suggest that some antibiotics may precipitate the development of complications. Antidiarrheal drugs should not be used.
ETEC is also primarily treated with fluid and electrolyte replacement. If the diarrhea is severe, antibiotics may be prescribed. Antidiarrheal drugs may help alleviate the symptoms but can keep the bacteria in the system longer.
EIEC is treated with antibiotics.
Complications require hospitalization, including intensive care treatment, renal dialysis, and blood transfusions. |
Source: Medical Disability Advisor
| Individuals with only the diarrhea phase of an E. coli intestinal infection usually have a complete recovery. ETEC and EIEC typically resolve without complications.
Of those with EHEC who develop HUS, one-third will continue to have long-term abnormal renal function. Some will require long-term renal dialysis. Approximately 8% will have long-term high blood pressure, seizures, blindness, and paralysis; with intensive care treatment, the death rate for HUS is 3% to 5% ("Escherichia Coli"). |
Source: Medical Disability Advisor
| Up to 7% of individuals with EHEC develop a life-threatening condition called hemolytic uremic syndrome (HUS) in the second week following onset of diarrhea. In HUS, the absorbed bacterial toxin destroys red blood cells and causes renal failure. Some individuals with HUS need to have part of their bowel removed (bowel resection). When absorbed into the bloodstream, E. coli toxins can also affect other organs such as the kidney. Prolonged or severe diarrhea can lead to severe dehydration and decreased blood pressure (hypovolemic shock). |
Source: Medical Disability Advisor
| Individuals who work with food or provide care to children or other individuals should be relieved of these duties until diarrhea has stopped and they have been cleared to return to work. Elimination of the diarrhea-producing E. coli is verified by two negative stool cultures collected at least 24 hours apart. If antibiotics were taken, the cultures should be collected at least 48 hours after the last dose of antibiotics. |
Source: Medical Disability Advisor
| If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case. Regarding diagnosis:
- Does individual have abdominal cramps, bloody or watery diarrhea, and/or fever?
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Did individual present with other systemic indications of infection (i.e., genitourinary symptoms, wound drainage, etc)? When did the symptoms begin?
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What did individual have to eat or drink 2 to 8 days prior to the diarrhea?
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Has individual traveled out of the country recently?
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Was there evidence of dehydration or electrolyte imbalance in the physical exam?
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Did physical exam reveal findings indicative of genitourinary or systemic infection (i.e., fever, tachycardia, tachypnea, wound exudates, genitourinary symptoms)?
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Was diagnosis of E. coli infection confirmed with appropriate cultures (i.e., stool cultures, urine cultures, blood cultures, wound cultures)?
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Was sensitivity testing done to identify appropriate antibiotic therapy?
Regarding treatment:
- Have symptoms of dehydration or electrolyte imbalance been treated as needed with intravenous fluid replacement?
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Has the appropriate antibiotic therapy been administered?
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Have the fever and other symptoms resolved with the treatment? If not, were cultures repeated to rule out the possibility of antibiotic resistance or secondary infection?
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Were appropriate changes or additions made to the current antibiotic treatment?
Regarding prognosis:
- Did individual receive prompt and appropriate supportive care and antibiotic treatment?
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Based on underlying cause, severity of symptoms and general health of individual, what was the expected outcome?
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Did individual experience any associated complications (systemic infection, shock, etc.) that could affect recovery and prognosis?
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Does the individual have any underlying conditions (i.e., chronic illness, immune suppression) that could affect ability to recover?
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Source: Medical Disability Advisor
| "Escherichia Coli 0157:H7." Centers for Disease Control and Prevention. 27 Jan. 2004. U.S. Department of Health and Human Services. 26 Nov. 2004 <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm>. |
Source: Medical Disability Advisor
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