In the Salmonella–mouse model of systemic infection, high dose inoculation results in the
multiplication of many of the cells present in the inoculum, rather than the clonal
amplification of a small number. This characteristic has allowed the development of methods
to screen multiple strains for either virulence attenuation or gene expression within the same
animal. Mixed infections with mutant and wild-type strains are used to provide a sensitive
measure of virulence attenuation referred to as the competitive index. We have recently …