The Role of Exoenzyme S in Pseudomonas aeruginosa Infections

We utilized genetic and immunological methods to determine the role of exoenzyme S in Pseudomonas aeruginosa infections. An exoenzyme S deficient mutant, 388 exslTn1, was compared to its S parent strain in the burned mouse model and neutropenic rat model. In both animal models the S- mutant was less virulent than its s parent strain. The s- mutant was, however, able to establish at the site of infection but it was unable to disseminate. We also developed an ELISA assay to quantitate S antibodies. We determined the ELISA titer and neutralization titer in serum from patients with P. aeruginosa infections, patients with acute infections due to other bacterial species and from healthy control individuals. Healthy individuals or patients infected with species other than P. aeruginosa had either no, or very low, antibody to exoenzyme S. Patients infected with exoenzyme S producing strains developed high titers of S antibody within 3 weeks. These data indicate that exoenzyme S is produced in vivo in humans. We also cloned and partially characterized and exoenzyme S gene from a Pseudomonas aeruginosa chromosomal DNA. The S gene was subcloned and localized to a 3Kb region as one end of an 8.2 Kb DNA fragment. We obtained the sequence for the first 22 amino acids of the amino terminus of the purified 49Kd exoenzyme S protein. Keywords Bacterial toxins, Bacterial vaccines.