Bacterial Invasion

Abstract

LET it be assumed that: (a) each organism invading a host has a chance λ of reaching a favourable site, and of afterwards undergoing a sequence of events which enable it to proliferate and result in the death (or infection) of the host; (b) each organism acts independently; (c) c inhaled organisms are necessary to produce the death (or infection) of 0.5 of the total of exposed animals; (d) the experimental animal population is large and homogeneous. Then the proportion S of animals remaining uninfected after the intake of n organisms each is given by: S = (1 — λ)ⁿ, and by definition 0.5 = (1 — λ)^c, Expressing n in units of c that is, n = fc, S = (1 — λ)^fc = 0.5f.