Friday, June 3, 2011

e coli : E. coli O157:H7—a foodborne pathogen


 
E. coli O157:H7 was first recognized as a foodborne pathogen in 1982 during an investigation into an outbreak of hemorrhagic colitis (bloody diarrhea) associated with the consumption of contaminated hamburgers (Riley, et al., 1983).  The following year, Shiga toxin (Stx), produced by the then little-known E. coli O157:H7, was identified as the real culprit. 
In the ten years following the 1982 outbreak, approximately thirty E. coli O157:H7 outbreaks were recorded in the United States (Griffin & Tauxe, 1991). The actual number that occurred is probably much higher because E. coli O157:H7 infections did not become a reportable disease (required to be reported to public health authorities) until 1987 (Keene et al., 1991 p. 60, 73).  As a result, only the most geographically concentrated outbreaks would have garnered enough attention to prompt further investigation (Keene et al., 1991 p. 583).  It is important to note that only about 10 percent of infections occur in outbreaks, the rest are sporadic. 
The CDC has estimated that 85 percent of E. coli O157:H7 infections are foodborne in origin (Mead, et al., 1999).  In fact, consumption of any food or beverage that becomes contaminated by animal (especially cattle) manure can result in contracting the disease.  Foods that have been identified as sources of contamination include ground beef, venison, sausages, dried (non-cooked) salami, unpasteurized milk and cheese, unpasteurized apple juice and cider (Cody, et al., 1999), orange juice, alfalfa and radish sprouts (Breuer, et al., 2001), lettuce, spinach, and water (Friedman, et al., 1999).  Pizza and cookie dough have also been identified as sources of E. coli outbreaks.
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