Outbreaks of Shiga Toxin-Related Poisoning

Foodborne outbreaks of Shiga toxin-producing bacteria occur with disturbing regularity. The two most common Shiga toxin-producing bacteria are Shigella spp. and the Shiga toxin-producing Escherichia coli (STEC). Among foodborne pathogens, they result in a disproportionately large share of hospitalizations, serious sequelae, and deaths. In 1982 the first reported outbreak of STEC was caused by an E. coli O157:H7 serotype in undercooked hamburger, but by 2008 it was estimated that most foodborne STEC disease was caused by other serotypes. As the food service industry has adopted more stringent cooking practices and as diets have changed, the sources of outbreaks have shifted as well. The two largest outbreaks on record were caused by consumption of uncooked radish and fenugreek sprouts. There are at least 200 different known strains of STEC found in farm animals, where they can propagate “below the radar” because farm animals lack the receptors that would make them vulnerable to Shiga toxins. Future outbreaks are likely to involve other uncooked foods and different strains of STEC, and they may be triggered by the agricultural practices, food processing and transportation conditions, and ecological factors that bring them together.