Dietary effects on the microbiological safety of food

The high mortality rate associated with human infections caused by Escheric hia coli strains of the serotype O157:H7 has brought to public attention th e importance of ruminants as reservoirs of food-borne pathogens. In additio n to established examples such as salmonella, campylobacter and listeria, r ecent evidence is emerging of the role of food in the transmission of Helic obacter pylori and Mycobacterium paratuberculosis. Food-borne pathogens har boured by ruminants are spread through shedding in the faeces and subsequen t faecal contamination of raw food. Ruminant shedding appears to be affecte d by diet and, of particular concern, may be increased during fasting regim ens imposed during transport to the slaughterhouse. The survival of food-bo rne pathogens in the ruminant gut is affected by many factors including mic robe-microbe interactions, interactions involving plant metabolites and the presence of inhibitory end-product metabolites such as short-chain fatty a cids. The potential importance of digesta flow and bacterial detachment in shedding of food-borne pathogens is discussed. Experimental procedures with dangerous pathogens have constraints, particularly in animal experimentati on. This situation may be overcome by the use of rumen-simulating fermenter s. One such system which, like the natural rumen, has a different turnover rate for solid and liquid digesta, was found to maintain rumen-like variabl es over an 11 d period. This system may prove useful for the study of dieta ry effects on food-borne pathogens.