E. coli 0157:H7 infection
Enterohemorrhagic E. coli is one of several intestinal types of E.coli that infect animals and humans. The O157:H7 strain is the member ofthe group most often associated with a particularly severe form of diarrhea and the most common cause of a unique, sometimes fatal syndrome (hemolytic-uremic syndrome [HUS]) that causes kidney failure (although this happensmainly in the very young and old). The bacteria was discovered in 1977, and first reports of infections followed in 1982.
E. coli accounts for about 2% of all cases of diarrhea in the Westernworld and at least one-third of cases of hemorrhagic colitis, a potentially deadly inflammation of the colon. The bacteria also accounts for the majorityof episodes of HUS, especially in children. Ten percent of individuals with E. coli O157:H7 infection develop HUS; 5% of those will die of the disease. Some who recover from HUS will be left with kidney damage.
The bacteria produces toxins that are lethal for intestinal cells and also damage the linings of blood vessels. Experts believe that this damage to bloodvessels results in the formation of clots, which eventually leads to HUS. After an incubation period of about 3-4 days, watery diarrhea begins. This rapidly progresses to bloody diarrhea in many victims, in which case the bowel movement may be mostly blood. Nausea and vomiting, along with low-grade fever, are also frequently present. Gastrointestinal symptoms last for about one week, and recovery is often spontaneous.
When a patient complains of bloody diarrhea, stool cultures can tentatively identify the bacteria. Further tests at specialized laboratories are usually needed, however, for confirmation of infection. Unfortunately, cultures are often negative or inconclusive if they are collected past 48 hours of the onsetof symptoms.
Uncomplicated cases of the infection usually clear up within ten days. It isuncertain whether antibiotics are helpful in treating E. coli O157:H7,and there is some evidence that they may actually be harmful. Dehydration resulting from diarrhea must be treated. Antimotility agents, which decrease the intestines' ability to contract, should not be used in any patient with bloody diarrhea.
E. coli O157:H7 is commonly found in cattle and poultry. Reports of apple cider contamination have occurred. Contaminated hamburger meat has been the most common source of infection, but other sources exist. Human-to-human transmission, mainly through contact with fecal matter, has also been identified in daycare centers.
Thorough cooking of all meat and poultry products and adhering to proper foodpreparation practices is the most effective way to avoid infection. Food irradiation methods are also being developed to sanitize food.