RESUMO
BACKGROUND: Pseudomonas aeruginosa (PA) is a common cause of respiratory infection and morbidity. Pseudomonas elastase is an important virulence factor regulated by the lasR gene. Whether PA elastase activity is associated with worse clinical outcomes in ICU patients is unknown. RESEARCH QUESTION: Is there an association between PA elastase activity and worse host outcomes in a cohort of ICU patients? METHODS: PA respiratory isolates from 238 unique ICU patients from two tertiary-care centers within the University of Pittsburgh Medical Center health system were prospectively collected and screened for total protease and elastase activity, biofilm production, antimicrobial resistance, and polymicrobial status. The association between pathogen characteristics and 30-day and 90-day mortality was calculated using logistic regression. For subgroup analysis, two patterns of early (≤72 h) and late sample (>72 h) collection from the index ICU admission were distinguished using a finite mixture model. Lung inflammation and injury was evaluated in a mouse model using a PA high elastase vs low elastase producer. RESULTS: PA elastase activity was common in ICU respiratory isolates representing 75% of samples and was associated with increased 30-day mortality (adjusted OR [95% CI]: 1.39 [1.05-1.83]). Subgroup analysis demonstrated that elastase activity was a risk factor for 30- and 90-day mortality in the early sample group, whereas antimicrobial resistance was a risk factor for 90-day mortality in the late sample group. Whole genome sequencing of high and low elastase producers showed that predicted loss-of-function lasR genotypes were less common among high elastase producers. Mice infected with a high elastase producer showed increased lung bacterial burden and inflammatory profile compared with mice infected with a low elastase producer. INTERPRETATION: Elastase activity is associated with 30-day ICU mortality. A high elastase producing clinical isolate confers increased lung tissue inflammation compared with a low elastase producer in vivo.
Assuntos
Proteínas de Bactérias/metabolismo , Estado Terminal , Unidades de Terapia Intensiva/estatística & dados numéricos , Pulmão , Metaloendopeptidases/metabolismo , Mortalidade , Pneumonia Bacteriana , Infecções por Pseudomonas , Pseudomonas aeruginosa , Animais , Correlação de Dados , Estado Terminal/mortalidade , Estado Terminal/terapia , Demografia , Modelos Animais de Doenças , Feminino , Humanos , Pulmão/imunologia , Pulmão/microbiologia , Masculino , Camundongos , Pessoa de Meia-Idade , Pneumonia Bacteriana/microbiologia , Pneumonia Bacteriana/mortalidade , Infecções por Pseudomonas/etiologia , Infecções por Pseudomonas/mortalidade , Pseudomonas aeruginosa/enzimologia , Pseudomonas aeruginosa/isolamento & purificação , Pseudomonas aeruginosa/patogenicidade , Respiração Artificial/estatística & dados numéricos , Estados Unidos/epidemiologia , Fatores de VirulênciaRESUMO
Thrombocytopenia is associated with worse outcomes in patients with acute respiratory distress syndrome, which is most commonly caused by infection and marked by alveolar-capillary barrier disruption. However, the mechanisms by which platelets protect the lung alveolar-capillary barrier during infectious injury remain unclear. We found that natively thrombocytopenic Mpl -/- mice deficient in the thrombopoietin receptor sustain severe lung injury marked by alveolar barrier disruption and hemorrhagic pneumonia with early mortality following acute intrapulmonary Pseudomonas aeruginosa (PA) infection; barrier disruption was attenuated by platelet reconstitution. Although PA infection was associated with a brisk neutrophil influx, depletion of airspace neutrophils failed to substantially mitigate PA-triggered alveolar barrier disruption in Mpl -/- mice. Rather, PA cell-free supernatant was sufficient to induce lung epithelial cell apoptosis in vitro and in vivo and alveolar barrier disruption in both platelet-depleted mice and Mpl -/- mice in vivo. Cell-free supernatant from PA with genetic deletion of the type 2 secretion system, but not the type 3 secretion system, mitigated lung epithelial cell death in vitro and lung injury in Mpl -/- mice. Moreover, platelet releasates reduced poly (ADP ribose) polymerase cleavage and lung injury in Mpl -/- mice, and boiling of platelet releasates, but not apyrase treatment, abrogated PA supernatant-induced lung epithelial cell cytotoxicity in vitro. These findings indicate that while neutrophil airspace influx does not potentiate infectious lung injury in the thrombocytopenic host, platelets and their factors protect against severe pulmonary complications from pathogen-secreted virulence factors that promote host cell death even in the absence of overt infection.