Incidence and Level of Exotoxin A in Proteolytic Cell-free Cultures of Clinical Isolates of Pseudomonas Aeruginosa Collected from Hospitals in Riyadh, Saudi Arabia

Mice lethality bioassay revealed that out of 102 proteolytic cell-free cultures of Pseudomonas aeruginosa only 17 (15%) were lethal with values of 19-48 LD50/ml. Antitoxin A antiserum neutralized the lethality providing evidence that the main lethal compound in the cell free cultures was exotoxin A. The neutralization also ruled out the lethal contribution of protease, elastase and phospholipase c. The presence of exotoxin A in a proteolytic environment may indicate less efficient proteolytic action at the stage of toxin production.