Infectious Dose

The infectious dose is the amount of agent that must be consumed to give rise to symptoms of foodborne illness and varies according to the agent and the consumer’s age and overall health. In the case of Salmonella, relatively large inoculums of 1 million to 1 billion organisms are necessary to produce symptoms in healthy human volunteers, as Salmonella bacteria are very sensitive to acid. An unusually high stomach pH level (low acidity) dramatically reduces the number of bacteria required to cause symptoms by a factor of between 10 and 100.