Pasteurella multocida is a Gram-negative coccobacillus that is both a normal commensal and a primary pathogen in a wide range of mammals and birds. P. multocida is responsible for several different animal disease syndromes within different host species; including avian cholera in fowl, haemorrhagic septicaemia in ungulates, shipping fever in cattle, atrophic rhinitis in swine and snuffles in rabbits. Many of the disease syndromes caused by P. multocida have a large economic impact on many agricultural industries. Despite the economic cost, the pathogenic mechanisms behind each disease are poorly understood.
Transposon-directed insertion site sequencing (TraDIS) can be used to identify genomic regions essential for the survival of a bacterium in a specific niche. TraDIS involves the production of a very large mutant library via transposon mutagenesis, ideally saturating the genome of the bacterium of interest. The mutant library is then grown in any condition of interest, the surviving mutants are recovered and the transposon-genomic DNA regions from all recovered bacteria are amplified and sequenced, allowing all transposon insertion sites to be identified. TraDIS is a negative selection method, and genomic regions lacking transposon insertion sites are assumed to be essential for growth under the condition of interest.
We have recently developed a Himar1-based TraDIS method for use in P. multocida and will screen this mutant library under a range of conditions, including growth in rich media, low iron conditions, chicken serum, and growth in chickens. These analyses will improve our understanding of how P. multocida causes disease, which will inturn allow the design of novel therapeutic strategies to combat P. multocida infections.