Ecology of Escherichia coli O157:H7 in Cattle: Interactions and Interventions

摘要

Shiga toxin-producing Escherichia coli (STEC) are an important cause of enteritis in humans, ranging in severity from mild to bloody diarrhea, and in children the condition may progress to hemolytic uremic syndrome (HUS) and even death. Approximately,500 O serotypes of E. coli have been shown to produce Shiga toxin and over 100 of these have been associated with human sporadic and epidemic diarrheal diseases. The most common STEC associated with human disease is E. coli O157:H7. Several non-0157 STEC serotypes, such as 026, 045, O103, 0111, 0121, and 0145, have emerged as important causes of enteritis and it is estimated that non-0157 serotypes account for 20 to 50% of STEC infections annually. Most cases of E. coli 0157 infections in humans are food-borne and foods implicated in transmission of the organism include beef and dairy products, and fruits and vegetables contaminated with cattle feces. Contamination of beef carcasses with E. coli O157:H7 occurs during harvest and is associated with both fecal and hide prevalence. E. coli 0157 is not a significant animal pathogen, except in colostrum-deprived or immune-suppressed neonatal calves and piglets. E. coli 0157 occurs in many animals but ruminants have the highest prevalence among the food-animal species. The organism colonizes in the gastrointestinal tract and is then shed in the feces. The hindgut is the major site of persistence of E. coli O157:H7 and there is evidence that mucosal epithelium proximal to the rectoanal junction may be thesite of preferential colonization.