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Bacterial and host factors affecting Pseudomonas aeruginosa colonization versus bacteremia in granulocytopenic
1Department of Laboratory Medicine, Johns Hopkins Hospital, Baltimore, Maryland 21205.
Abstract:
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 less than 0.002); piperacillin, 44% vs. 86% (P less than 0.006); and cefsulodin, 60% vs. 90% (P less than 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 less than 0.0002) and bacteremia patients (P less than 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.
Insights
Pseudomonas aeruginosa sepsis in granulocytopenic patients is linked to antibiotic resistance and low iron-binding capacity. These factors may predict P. aeruginosa bacteremia risk in vulnerable oncology patients.
Area of Science:
- Infectious Diseases
- Hematology
- Microbiology
Background:
- Granulocytopenic patients are susceptible to Pseudomonas aeruginosa infections.
- Understanding bacterial and host factors is crucial for predicting P. aeruginosa colonization and bacteremia.
Purpose of the Study:
- To evaluate bacterial virulence factors and host iron-binding capacity in P. aeruginosa colonization and bacteremia among oncology patients.
- To identify potential predictors of P. aeruginosa sepsis in granulocytopenic individuals.
Main Methods:
- Analyzed 132 P. aeruginosa isolates from 44 oncology patients for serotype, serum sensitivity, antibiotic susceptibility, and enzyme/pigment production.
- Assessed host total iron-binding capacity (TIBC) in acute leukemia patients (controls, colonization only, bacteremia).
Main Results:
- No significant differences in bacterial enzyme activity, pigment production, or serum sensitivity between bacteremia and colonization strains.
- Bacteremia strains showed significantly lower susceptibility to ticarcillin, piperacillin, and cefsulodin compared to colonizing strains.
- Lower TIBC nadir in control patients compared to colonization and bacteremia patients; bacteremia correlated with TIBC nadir.
Conclusions:
- Beta-lactam antibiotic resistance in P. aeruginosa may contribute to bacteremia in granulocytopenic patients.
- Host iron-binding capacity, specifically TIBC nadir, appears to be a significant factor in P. aeruginosa sepsis development.
- Antibiotic resistance and host iron status are potential predictors of P. aeruginosa sepsis in immunocompromised patients.