Escherichia coli (or simply E. coli) is one of the many groups of bacteria that live in the intestines of healthy humans and most warm-blooded animals. E. coli bacteria help maintain the balance of normal intestinal flora (bacteria) against harmful bacteria and synthesize or produce some vitamins.
However, there are hundreds of types or strains of E. coli bacteria. Different strains of E. coli have different distinguishing characteristics.
A particular strain of E.coli known as E. coli O157:H7 causes a severe intestinal infection in humans. It is the most common strain to cause illness in people. It can be differentiated from other E. coli by the production of a potent toxin that damages the lining of the intestinal wall causing bloody diarrhea. It is also known as enterohemorrhagic E. coli infection.
The Centers for Disease Control and Prevention (CDC) reports about 70,000 cases of this type of E. coli infection occur in the United States each year.
In 1982, E. coli O157:H7 was initially identified as the cause of bloody diarrhea from eating undercooked or raw hamburger meat that was contaminated with the bacteria. Since that time, outbreaks of E. coli O157:H7 have been associated with other types of foods such as spinach, lettuce, sprouts, unpasteurized milk, apple juice, apple cider, salami, and well water or surface water areas frequently visited by animals. Outbreaks have also been traced to animals at petting zoos and day care centers.
E. coli O157:H7 is found in the intestines of healthy cattle, goats, deer, and sheep. According to the CDC, the transmission of these bacteria to humans may occur in the following manner:
However, the CDC also indicates the way E. coli O157:H7 is transmitted may change over time.
An E. coli infection can make a person very ill. Symptoms usually begin two to five days after ingesting contaminated food or liquids, and may last for eight days. The following are some of the most common symptoms associated with E. coli O157:H7. However, each person may experience symptoms differently;
Symptoms may range from none to HUS. In HUS, an individual's red blood cells (oxygen-carrying cells in the bloodstream) are destroyed and the kidneys stop working. Approximately 5 percent to 10 percent of infections can result in this syndrome. Children and the elderly may be more prone to develop this complication, which may be life-threatening.
E. coli O157:H7 can be confirmed with a special stool culture. Stool samples are tested to compare with the source or contaminated food that has caused an outbreak. The CDC calls this "DNA fingerprinting" of E. coli.
Antibiotics are not used with this type of infection, and taking them may increase the risk of HUS. In addition, antidiarrheal medications, such as loperamide (Imodium) are not used. Recovery for most people with this illness usually occurs within five to 10 days.
If a person develops HUS, hospitalization in an intensive care unit may be required. Treatment may include blood transfusions and kidney dialysis. According to the CDC, three to five percent of persons who develop HUS may die from this complication.
CDC recommendations for prevention of the infection include:
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