Minimal infective dose

The concept of a minimal infective dose (MID), also known as the infectious dose, 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, to know the dose ingested, it is also necessary to know the mass of the portion:

${\displaystyle {\ce {d\ =\ c\times m}}}$

where:

• ${\displaystyle {\ce {d}}}$ = number of bacteria i.e. dose
• ${\displaystyle {\ce {c}}}$ = concentration of bacteria
• ${\displaystyle {\ce {m}}}$ = 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 fixed its maximum concentration at 100 L. monocytogenes per gram.