Exotoxin production by clinical isolates of Pseudomonas aeruginosa

Abstract

75 consecutive clinical Pseudomonas aeruginosa isolates were tested for in vitro exotoxin production. Exotoxin was demonstrated in culture filtrates biologically, by its ability to produce characteristic dermonecrotic lesions in guinea pigs, and serologically, by counterimmunoelectrophoresis (CIE) with rabbit antiserum elicited with purified exotoxin. By these 2 methods, exotoxin was detected in 87 and 89% of P. aeruginosa strains, respectively (r = 0.48, P < 0.001). Although less sensitive than CIE in detecting exotoxin, immunodiffusion demonstrated a reaction of antigenic identity in most cases. Exotoxin was produced by all 7 Fisher-Devlin immunotypes and by untypable strains. In contrast, exotoxin was not detected in the culture filtrates of 16 non-aeruginosa pseudomonas isolates and 48 non-pseudomonas organisms. The production of biologically similar and antigenically closely related exotoxins is thus a characteristic of the majority of P. aeruginosa strains derived from diverse clinical sources.