Bacteremia Due to Pseudomonas aeruginosa: Use of a Combined Typing System in an Eight-Year Study

P aeruginosa bacteremia is a nosocomial disease with a high mortality occurring in colonized, debilitated, and leukopenic patients and in those receiving immunosuppressive and antimicrobial agents [2]. Outbreaks of P aeruginosa bacteremia have often been associated with environmental reservoirs [3]. The 190 strains of P aeruginosa described in this study represent single isolates from bacteremic patients during an eight-year period. Representing about 50% of total isolates, the most common pyocin types were lb, 3, and 10, immunotypes 1, 2, and 3 + 7, and serotypes 11, 6, and 1. Of the 37 known pyocin types, only 10 were represented in this study. All seven immunotypes and 14 of 17 serotypes were found. The overall typability for each of the three techniques was 88%-90%; however, the largest numbers of typable patterns were found when all three typing methods or pyocin and either immunotyping or serotyping were used. The smallest number of typing patterns occurred when immunotyping and serotyping were performed together. Correlation among the following types was greater than 50%; pyo 3:immuno 1:sero 6; pyo 10:immuno 2:sero 11, and pyo NI:immuno 4:sero 1. Upon repeated testing the reproducibility of types for each technique was 98%-100%. For the most precise epidemiologic studies of P aeruginosa infections all three typing methods should be employed.