Type III Protein Secretion Is Associated with Death in Lower Respiratory and Systemic<i>Pseudomonas aeruginosa</i>Infections

TLDR

Pseudomonas aeruginosa secretes toxins via a type III–mediated pathway, a feature that may help distinguish lethal infections from colonization and guide therapy in critically ill patients. The study aimed to determine whether expression of type III secretory proteins in P. aeruginosa isolates is associated with human illness. Immunoblot analysis of 108 patient isolates from respiratory or blood cultures was performed to detect type III secretory protein expression.

Abstract

The ability of Pseudomonas aeruginosa to secrete specific toxins using the type III–mediated pathway has been reported. To determine the association of this phenotype with human illness, immunoblot analysis was used to detect expression of type III secretory proteins in P. aeruginosa isolates from respiratory tract or blood cultures of 108 consecutive patients. Relative risk of mortality was 6-fold greater with expression of the type III secretory proteins ExoS, ExoT, ExoU, or PcrV. Phenotype was independently correlated with toxicity in cellular and murine models. Prevalence of this phenotype was significantly higher in acutely infected patients than in chronically infected patients with cystic fibrosis. These results suggest that the type III protein secretion system is integral to increased P. aeruginosa virulence. A positive phenotype is a predictor of poor clinical outcome. In the future, such analyses may help distinguish potentially lethal infection from colonization and help determine appropriate therapy for critically ill patients