Clinical significance of serum antibody responses to exotoxin A and type-specific lipopolysaccharides in patients with Pseudomonas aeruginosa infections.

Serum antibodies to Pseudomonas aeruginosa exotoxin A and immunotype-specific lipopolysaccharides were evaluated as diagnostic and prognostic markers in patients with Pseudomonas disease. Hemagglutination titers to exotoxin A were 1:1,024 or higher and/or showed a fourfold acute-to-convalescent increase in 17 of 25 (68 percent) patients infected with Pseudomonas compared with only one of seven (15 percent) colonized (p = 0.01) and two of 24 (8 percent) culture-negative patients (p less than 0.001). By comparison, hemagglutination titers to the lipopolysaccharide of patients' Pseudomonas isolates were 1:1,024 or higher or showed a fourfold increase in only four of 17 (24 percent) infected patients and in none of six (0 percent) colonized patients (p = 0.96). Serial antibody titers to exotoxin A provided serologic confirmation of invasive disease, distinguished infection from colonization, and, in the case of decreasing titers, indicated successful therapy. It is concluded that serum antibodies to exotoxin A are useful serologic markers for the clinical assessment of Pseudomonas infections in man.