Bacterial and host factors affecting Pseudomonas aeruginosa colonization versus bacteremia in granulocytopenic patients

In order to evaluate bacterial factors which might predispose to P. aeruginosa colonization or bacteremia in the granulocytopenic patient, 132 isolates recovered from 44 oncology patients were evaluated for antigenic serotype, iron correctable sensitivity to pooled human serum, antibiotic susceptibility, production of lecithinase, elastase, protease, gelatinase, pyocyanin and pyoverdin. Similarly, potential host factors, primarily total iron binding capacity, were evaluated in a subpopulation of acute leukemia patients composed of 13 control patients without P. aeruginosa cultured during their hospital course, 11 colonization only patients and 15 P. aeruginosa bacteremia patients. No significant differences were observed between strains recovered from bacteremia vs. colonization patients for extracellular enzyme activity, pigment production, serum sensitivity and antigenic serotype. Significant differences were observed between bacteremia and colonizing strains for antibiotic susceptibility to ticarcillin, 40% vs. 76% (P < 0.002); piperacillin, 44% vs. 86% (P < 0.006); and cefsulodin, 60% vs. 90% (P < 0.02). Of the host factors evaluated in the acute leukemia patients, significant differences were observed between the TIBC nadir of control patients and both colonization patients (P < 0.0002) and bacteremia patients (P < 0.0004). P. aeruginosa bacteremia was associated with the temporal occurrence of TIBC nadir and the detection of the organism. These data suggest a possible role for beta-lactam antibiotic resistance and host iron binding capacity as determinants and possible predictors of P. aeruginosa sepsis in the granulocytopenic patient.