Contribution of exoenzyme S to the virulence of Pseudomonas aeruginosa.

Exoenzyme S is an extracellular ADPR transferase produced by P. aeruginosa. Forms of this enzyme that have thus far been purified are not toxic, however, exoenzyme S clearly contributes to the virulence of strain 388. Thus, a Tn1 mutant deficient in exoenzyme S was found to be markedly less virulent than its exoenzyme S-producing parental strain in both a burned mouse infection model and a rat chronic lung infection model. Exoenzyme S does not appear to contribute to initial colonization of the rat lung or the burned mouse skin. Exoenzyme S does, however, appear to contribute to local tissue damage in the rat lung, and to dissemination of P. aeruginosa from the skin into the blood and distant organs of the burned mouse. Perhaps our most important observation is that specific antibody against exoenzyme S confers a high level of protection against subsequent infection of burned mice. While these results must be extended to include additional strains they are encouraging, and they underscore the relative importance of exoenzyme S in the pathogenesis of P. aeruginosa infections.