Passive immune therapy for experimental Pseudomonas aeruginosa pneumonia in the neutropenic host

Studies were conducted in guinea pigs, myelosuppressed by cyclophosphamide, for determination of whether passive immune therapy for Pseudomonas aeruginosa pneumonia would be useful in the setting of neutropenia. Groups of infected animals (14 per group) were treated with a single intravenous infusion of hyperimmune IgG antibody to P. aeruginosa (PA-IGIV; 500 mg/kg), tobramycin (1.7 mg/kg per 8 hr), ticarcillin (120 mg/kg per 6 hr), or combinations of these regimens. Control groups received intravenous albumin solution. Survival rates were 0% with albumin only, 0% with PA-IGIV, 43% with tobramycin (P less than .05), 86% with tobramycin plus PA-IGIV (P less than .05 vs. tobramycin alone), 7% with ticarcillin, and 43% with ticarcillin plus PA-IGIV (.05 less than P less than .10 vs. ticarcillin alone). Additive intrapulmonary killing of P. aeruginosa and prevention of bacteremia were observed in animals treated with tobramycin plus PA-IGIV compared with either treatment alone. Thus, passive immune therapy for P. aeruginosa pneumonia may be useful in the neutropenic host, but only when used in conjunction with antimicrobial agents.