Listeria in effluents from the food-processing industry

There is general agreement that listeriosis has a significant impact on Man as well as on animals. Listeria monocytogenes has been isolated from the faeces of healthy human and animal carriers and from various environmental sources. L. monocytogenes is the pathogenic species most responsible for abortion, septicaemia and meningitis in animals and Man. Listeria ivanovii is a primary cause of abortion in animals. Owing to a number of epidemics and single cases caused by food contaminated with L. monocytogenes, listeriosis has received more attention in the past ten years than ever before. Entry of the organism into food-processing plants is primarily caused by animals which excrete Listeria in their faeces. Other sources of entry are raw foods of animal origin and personnel in food establishment. Proliferation of Listeria is promoted by high humidity and nutrient waste in certain food production plants. Removal of Listeria is almost impossible by routine disinfection. Listeria-contaminated sites pose a serious risk of recontamination of food-processing equipment and processed foods. Moreover, such sites represent an inexhaustible source of entry for Listeria in plant effluents. There is no denying that effluents from food-processing plants increase the spread of Listeria in the environment. However, considering the existence of other sources of entry, such as human and animal husbandry wastes, and that circulation and recontamination within the environment itself are also possible, this may not be a particularly important risk.