Experimental studies of the pathogenesis of Pseudomonas aeruginosa infection: evidence for the in-vivo production of a lethal toxin.

Evidence is presented that a lethal toxin is produced by P. aeruginosa growing in the burned skin of experimental mice. After injection of approximately 100 P. aeruginosa cells into the burned skin there was a rapid proliferation of organisms at the site of inoculation. When the organisms in the burned skin tissue reached a critical concentration, there was generalised toxaemia with subsequent mortality; the process was not reversible at this stage, even by reducing substantially the numbers of infecting organisms. However, when the reduction was accompanied by administration of rabbit serum prepared against filter-sterilised extracts of infected burned tissues, approximately 40% of the animals survived for at least 96 h. The data suggests that the antiserum afforded protection by inactivating a toxin produced by the organisms growing in the infected burned tissues rather than by further reducing the numbers of infecting organisms.