Identification of genes required for the fitness of subsp. in whole equine blood and hydrogen peroxide.

The availability of next-generation sequencing techniques provides an unprecedented opportunity for the assignment of gene function. subspecies is the causative agent of strangles in horses, one of the most prevalent and important diseases of equids worldwide. However, the live attenuated vaccines that are utilized to control this disease cause adverse reactions in some animals. Here, we employ transposon-directed insertion-site sequencing (TraDIS) to identify genes that are required for the fitness of in whole equine blood or in the presence of HO to model selective pressures exerted by the equine immune response during infection. We report the fitness values of 1503 and 1471 genes, representing 94.5 and 92.5 % of non-essential genes in , following incubation in whole blood and in the presence of HO, respectively. Of these genes, 36 and 15 were identified as being important to the fitness of in whole blood or HO, respectively, with 14 genes being important in both conditions. Allelic replacement mutants were generated to validate the fitness results. Our data identify genes that are important for to resist aspects of the immune response , which can be exploited for the development of safer live attenuated vaccines to prevent strangles.