Role of Motility in the Endogenous Pseudomonas aeruginosa Sepsis after burn

We investigated the relationship between bacterial motility and the lethal endogenous sepsis after burn in mice orally challenged with Pseudomonas aeruginosa, by using motility mutants. The mortality rates of postburn endogenous sepsis in mice orally challenged with low-motility mutants (strains B16-40 and B16-46) were 12% and 7.7%, respectively. By contrast, the mortality rates in mice who had been fed a high-motility mutant (B16-52) or the parental P. aeruginosa B16 (a high-motility strain) were 36% and 33%, respectively. Significant differences were found for mortality rates in groups fed the high-motility or lowmotility strains. A multiple regression analysis examining the effect of motility, number of cecal P. aeruginosa cells, and production of exotoxin A and total protease on the murine mortality rates associated with the 3 motility mutants and the parental strain showed a linear relationship between murine mortality and bacterial motility. In addition, when human monoclonal antibody specific for type-b flagella proteins of P. aeruginosa was intravenously administrated to mice orally challenged with P. aeruginosa B16, the mortality rate significantly decreased to 5.6%, compared with 33% in similar mice given intravenous saline. These results suggest that the occurrence of the lethal endogenous sepsis after burn in mice was closely related to the motility of the P. aeruginosa colonized in their intestinal tract, and that motility is an important virulence factor in endogenous P. aeruginosa sepsis after burn injury.