Minimal infective dose

The concept of minimal infective dose (MID) has traditionally been used for infectious bacteria that contaminate foods. MID was defined as the number of bacteria ingested (the dose) from which a pathology is observed in the consumer. Examples such as this are found in textbooks: to cause gastrointestinal disorders, the food must contain more than 100,000 Salmonella per gram. However, in such a formulation, an inaccuracy immediately becomes apparent: to know the dose ingested, concentration is not enough. It is also necessary to know the mass of the portion: d\ =\ c \times m where: d = number of bacteria i.e. dose c = concentration of bacteria m = mass Nevertheless, this formulation has served as a basis for reasoning to establish the maximum concentrations permitted by the microbiological regulatory criteria intended to protect the health of consumers. Thus in 1992, as the outbreaks previously caused by Listeria monocytogenes involved only food containing more than 1000 L. monocytogenes cells per gram, lawmakers on both sides of the Atlantic - keeping a margin of safety - fixed its maximum concentration at 100 L. monocytogenes per gram. The concept of a dose-response relationship developed from 1995 onward, as quantitative risk assessment matured as a discipline within the field of food safety. An infectious bacterium in a food can cause various effects: diarrhea, vomiting, sepsis, meningitis, abortion, Guillain-Barré syndrome, death, etc. As the dose increases, the severity of the pathological effects increases, and a "dose-effect relationship" can often be established. For example, the higher the dose of Salmonella, the more diarrhea occurs soon after ingestion. However, among people who have ingested the same dose, not all are affected. The proportion of people affected is called the response. The dose-response relationship for a given effect (e.g., diarrhea) is therefore the relationship between the dose and the likelihood of experiencing this effect.