E coli 0157 disease organism that lives happily in the guts of cattle. Infection in human beings kills, or leaves victims without functioning kidneys. Citrobacter freundii lives in pigs' guts and is also potentially lethal. If manure is pasteurised, or if you properly cook contaminated food, then the organism is killed. The problem is to guarantee that this is done.
Oversights do occur.
Two outbreaks of E coli 0157 in the US were traced to organic strawberries and lettuce. Organic farmers use sulphur as a weak pesticide. But sulphur contains lead, a known danger. What is not known is how much of the lead is transferred to the food we eat. Similarly, organic farmers are allowed to spray crops with bacterial spores to act as a general-purpose insecticide.