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. 2012 Apr;40(4):1157-63.
doi: 10.1097/CCM.0b013e3182377906.

Clinical outcomes of type III Pseudomonas aeruginosa bacteremia

Ali A El-Solh  1 , Angela Hattemer, Alan R Hauser, Ahmad Alhajhusain, Hardik Vora
Affiliations

Clinical outcomes of type III Pseudomonas aeruginosa bacteremia

Ali A El-Solh et al. Crit Care Med. 2012 Apr.

Abstract

Background: Pseudomonas aeruginosa bacteremia is a serious and life-threatening infection associated with high mortality. Among the multitude of virulence determinants possessed by P. aeruginosa, the type 3 secretion system has been implicated with more acute and invasive infection in respiratory diseases. However, the relationship between the type 3 secretion system and clinical outcomes in P. aeruginosa bacteremia has not been investigated.

Objectives: To determine the association between the type 3 secretion system virulence factor in P. aeruginosa bloodstream infection and 30-day mortality.

Design: Retrospective analysis of 85 cases of P. aeruginosa bacteremia.

Setting: Tertiary care hospital.

Interventions: Bacterial isolates were assayed in vitro for secretion of type 3 exotoxins (ExoU, ExoT, and ExoS). Strain relatedness was analyzed using randomly amplified polymorphic DNA polymerase chain reaction genotyping. Antimicrobial susceptibilities were determined by means of the Kirby-Bauer disk-diffusion test.

Measurements and main results: At least one of the type 3 secretion system proteins was detected in 37 out of the 85 isolates (44%). Septic shock was identified in 43% of bacteremic patients with type 3 secretion system+ isolates compared to 23% of patients with type 3 secretion system- isolates (p = .12). A high frequency of resistance in the type 3 secretion system+ isolates was observed to ciprofloxacin (59%), cefepime (35%), and gentamicin (38%). There was a significant difference in the 30-day cumulative probability of death after bacteremia between secretors and nonsecretors (p = .02). None of the type 3 secretion system+ patients who survived the first 30 days had a P. aeruginosa isolate which exhibited ExoU phenotype.

Conclusions: The expression of type 3 secretion system exotoxins in bacteremic isolates of P. aeruginosa confers poor clinical outcomes independent of antibiotic susceptibility profile.

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Figures

Figure 1
Figure 1
Immunoblot analysis showing the type III protein secretion phenotypes of representative P. aeruginosa isolates. Individual isolates were grown under conditions that induced type III protein secretion. Immunoblot analysis was then performed on culture supernatants using a mixture of antisera against type III exotoxins.
Figure 2
Figure 2
DNA genotyping of representative Pseudomonas aeruginosa isolates by repetitive-element-based polymerase chain reaction assay. Samples with identical banding patterns were considered to be related and assigned a single RAPD type. Samples with patterns that differed by one band were considered possibly related. Samples that differed by two or more bands were considered unrelated.
Figure 3
Figure 3
Kaplan-Meier probability estimate for 30-day mortality of P. aeruginosa bacteremia according to type III secretion phenotype. The broken line represents patients with bacteremia caused by P. aeruginosa type III secretion phenotype; the solid line represents patients with bacteremia caused by type III non secretory phenotype.
See this image and copyright information in PMC

Comment in

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