The potential for the control of Escherichia coli O157 in farm animals

The presence of Escherichia coli O157 in the faeces of farm animals appears to provide a primary route for human infection, either through physical co ntact or by contamination of the food chain. Controlling the survival and p roliferation of this pathogen in the ruminant gut could offer a measure of protection in the short term, and ultimately complement alternative biotech nological based solutions. Normally, E. coli is greatly outnumbered in the ruminant gut by anaerobic bacteria, producers of weak acids inhibitory to t he growth of this species. Withdrawal of feed prior to animal slaughter red uces the concentration of these acids in the gut and may be accompanied by the proliferation of E. roll. There are conflicting reports concerning the effects of changes in the ruminant diet upon faecal shedding of E. coli O15 7. It is contended that it is important to identify animal husbandry method s or feed additives that may be accompanied by an increased risk of prolife ration of this pathogen. Greater understanding of the mechanisms involved i n bacterial survival in the presence of weak acids, in the interactions bet ween E. coli and other gut bacteria, and of the effects of some antibacteri al plant secondary plant compounds on E. coli, could lead to the developmen t of novel control methods.