Which number of infecting bacteria is of clinical relevance?

The infective dose is the number of microorganisms required to produce infection in man. This value varies according to the mode of transmission, the virulence of the infecting agent and the host defense. The individual infective dose bears important implications with regard to epidemiology, prevention and therapy of the given infection. Theoretical remarks and relevant data from the literature are presented to help in the assessment of this basic problem in bacterial infectious diseases.