Tom van der Poll

Serial changes in soluble triggering receptor expressed on myeloid cells in the lung during development of ventilator-associated pneumonia

ObjectiveTo determine the diagnostic role of soluble triggering receptor expressed on myeloid cells (sTREM)-1 in non-directed bronchial lavage fluid in ventilator-associated pneumonia (VAP).DesignNon-directed bronchial lavage fluid and plasma were collected on alternate days in critically ill mechanically ventilated patients from the start of ventilatory support until complete weaning from the ventilator. Soluble TREM-1 levels were measured by an enzyme-linked immunosorbent assay.SettingA general adult medical and surgical university hospital intensive care unit.PatientsNine patients who developed VAP and 19 patients who did not develop VAP (controls).ResultsPlasma levels of sTREM-1 did not change significantly in either patient group. While in controls concentrations of sTREM-1 in non-directed bronchial lavage fluid did not change significantly over time, in patients who developed VAP levels of sTREM-1 in non-directed bronchial lavage fluid increased towards the diagnosis of VAP. A cut-off value for non-directed bronchial lavage fluid sTREM-1 levels of 200xa0pg/ml on the day of VAP had a diagnostic sensitivity of 75% and a specificity of 84%. Sensitivity increased when taking into account all sTREM-1 levels higher than 200xa0pg/ml from the 6-day period before the day of diagnosis that were preceded by an increase of at least 100xa0pg/ml (sensitivity 88%, specificity 84%).ConclusionsSoluble TREM-1 is a potential biomarker of VAP.

Bench-to-bedside review: Damage-associated molecular patterns in the onset of ventilator- induced lung injury

Mechanical ventilation (MV) has the potential to worsen pre-existing lung injury or even to initiate lung injury. Moreover, it is thought that injurious MV contributes to the overwhelming inflammatory response seen in patients with acute lung injury or acute respiratory distress syndrome. Ventilator-induced lung injury (VILI) is characterized by increased endothelial and epithelial permeability and pulmonary inflammation, in which the innate immune system plays a key role. A growing body of evidence indicates that endogenous danger molecules, also termed damage-associated molecular patterns (DAMPs), are released upon tissue injury and modulate the inflammatory response. DAMPs activate pattern recognition receptors, may induce the release of proinflammatory cytokines and chemokines, and have been shown to initiate or propagate inflammation in non-infectious conditions. Experimental and clinical studies demonstrate the presence of DAMPs in bronchoalveolar lavage fluid in patients with VILI and the upregulation of pattern recognition receptors in lung tissue by MV. The objective of the present article is to review research in the area of DAMPs, their recognition by the innate immune system, their role in VILI, and the potential utility of blocking DAMP signaling pathways to reduce VILI in the critically ill.

ENTEROCOCCAL SURFACE PROTEIN ESP IS NOT ESSENTIAL FOR CELL ADHESION AND INTESTINAL COLONIZATION OF ENTEROCOCCUS FAECIUM IN MICE

BackgroundEnterococcus faecium has globally emerged as a cause of hospital-acquired infections with high colonization rates in hospitalized patients. The enterococcal surface protein Esp, identified as a potential virulence factor, is specifically linked to nosocomial clonal lineages that are genetically distinct from indigenous E. faecium strains. To investigate whether Esp facilitates bacterial adherence and intestinal colonization of E. faecium, we used human colorectal adenocarcinoma cells (Caco-2 cells) and an experimental colonization model in mice.ResultsNo differences in adherence to Caco-2 cells were found between an Esp expressing strain of E. faecium (E1162) and its isogenic Esp-deficient mutant (E1162Δesp). Mice, kept under ceftriaxone treatment, were inoculated orally with either E1162, E1162Δesp or both strains simultaneously. Both E1162 and E1162Δesp were able to colonize the murine intestines with high and comparable numbers. No differences were found in the contents of cecum and colon. Both E1162 and E1162Δesp were able to translocate to the mesenteric lymph nodes.ConclusionThese results suggest that Esp is not essential for Caco-2 cell adherence and intestinal colonization or translocation of E. faecium in mice.

Plasma suPAR as a prognostic biological marker for ICU mortality in ARDS patients

PurposeWe investigated the prognostic value of plasma soluble urokinase plasminogen activator receptor (suPAR) on dayxa01 in patients with the acute respiratory distress syndrome (ARDS) for intensive care unit (ICU) mortality and compared it with established disease severity scores on dayxa01.MethodssuPAR was determined batchwise in plasma obtained within 24xa0h after admission.Results632 ARDS patients were included. Significantly (Pxa0=xa00.02) higher median levels of suPAR were found with increasing severity of ARDS: 5.9xa0ng/ml [IQR 3.1–12.8] in mild ARDS (nxa0=xa082), 8.4xa0ng/ml [IQR 4.1–15.0] in moderate ARDS (nxa0=xa0333), and 9.0xa0ng/ml [IQR 4.5–16.0] in severe ARDS (nxa0=xa0217). Non-survivors had higher median levels of suPAR [12.5xa0ng/ml (IQR 5.1–19.5) vs. 7.4xa0ng/ml (3.9–13.6), Pxa0<xa00.001]. The area under the receiver operator characteristic curve (ROC-AUC) for mortality of suPAR (0.62) was lower than the ROC-AUC of the APACHExa0IV score (0.72, Pxa0=xa00.007), higher than that of the ARDS definition classification (0.53, Pxa0=xa00.005), and did not differ from that of the SOFA score (0.68, Pxa0=xa00.07) and the oxygenation index (OI) (0.58, Pxa0=xa00.29). Plasma suPAR did not improve the discrimination of the established disease severity scores, but did improve net reclassification of the APACHE score (29xa0%), SOFA score (23xa0%), OI (38xa0%), and Berlin definition classification (39xa0%).ConclusionAs a single biological marker, the prognostic value for death of plasma suPAR in ARDS patients is low. Plasma suPAR, however, improves the net reclassification, suggesting a potential role for suPAR in ICU mortality prediction models.

Cecal ligation and puncture induced sepsis impairs host defense against Enterococcus faecium peritonitis.

PurposeMultiresistant and vancomycin resistant Enterococcus faecium (VRE) can cause serious infections in hospitalized patients with various co-morbid diseases. We investigated the course of VRE peritonitis after cecal ligation and puncture (CLP)-induced sepsis and compared this to sham operated mice.MethodsMice were subjected to CLP or sham surgery. Forty-eight hours thereafter four groups were created by subjecting mice to peritoneal injection of either VRE or saline.ResultsMice infected with VRE after CLP were severely impaired in eliminating VRE from the peritoneal cavity and distant body sites. These mice failed to mount an early inflammatory response at the primary site of VRE infection. VRE superinfection did not influence CLP-induced organ damage or polymicrobial bacterial loads.ConclusionsSublethal polymicrobial sepsis greatly facilitates infection and dissemination of VRE. VRE does not influence the course of CLP-induced sepsis.

Update of the Preventive Antibiotics in Stroke Study (PASS): statistical analysis plan

BackgroundInfections occur in 30% of stroke patients and are associated with unfavorable outcomes. Preventive antibiotic therapy lowers the infection rate after stroke, but the effect of preventive antibiotic treatment on functional outcome in patients with stroke is unknown. The PASS is a multicenter, prospective, phase three, randomized, open-label, blinded end-point (PROBE) trial of preventive antibiotic therapy in acute stroke. Patients are randomly assigned to either ceftriaxone at a dose of 2 g, given every 24 h intravenously for 4 days, in addition to standard stroke-unit care, or standard stroke-unit care without preventive antibiotic therapy. The aim of this study is to assess whether preventive antibiotic treatment improves functional outcome at 3 months by preventing infections. This paper presents in detail the statistical analysis plan (SAP) of the Preventive Antibiotics in Stroke Study (PASS) and was submitted while the investigators were still blinded for all outcomes.ResultsThe primary outcome is the score on the modified Rankin Scale (mRS), assessed by ordinal logistic regression analysis according to a proportional odds model. Secondary analysis of the primary outcome is the score on the mRS dichotomized as a favorable outcome (mRS 0 to 2) versus unfavorable outcome (mRS 3 to 6). Secondary outcome measures are death rate at discharge and 3 months, infection rate during hospital admission, length of hospital admission, volume of post-stroke care, use of antibiotics during hospital stay, quality-adjusted life years and costs. Complications of treatment, serious adverse events (SAEs) and suspected unexpected serious adverse reactions (SUSARs) are reported as safety outcomes.ConclusionsThe data from PASS will establish whether preventive antibiotic therapy in acute stroke improves functional outcome by preventing infection and will be analyzed according to this pre-specified SAP.Trial registrationCurrent controlled trials;ISRCTN66140176. Date of registration: 6 April 2010.

Granzyme A impairs host defense during Streptococcus pneumoniae pneumonia

Streptococcus pneumoniae is the most common causative pathogen in community-acquired pneumonia (CAP). Granzyme A (GzmA) is a serine protease produced by a variety of cell types involved in the immune response. We sought to determine the role of GzmA on the host response during pneumococcal pneumonia. GzmA was measured in bronchoalveolar lavage fluid (BALF) harvested from CAP patients from the infected and contralateral uninfected side and in lung tissue slides from CAP patients and controls. In CAP patients, GzmA levels were increased in BALF obtained from the infected lung. Human lungs showed constitutive GzmA expression by both parenchymal and nonparenchymal cells. In an experimental setting, pneumonia was induced in wild-type (WT) and GzmA-deficient (GzmA(-/-)) mice by intranasal inoculation of S. pneumoniae In separate experiments, WT and GzmA(-/-) mice were treated with natural killer (NK) cell depleting antibodies. Upon infection with S. pneumoniae, GzmA(-/-) mice showed a better survival and lower bacterial counts in BALF and distant body sites compared with WT mice. Although NK cells showed strong GzmA expression, NK cell depletion did not influence bacterial loads in either WT or GzmA(-/-) mice. These results implicate that GzmA plays an unfavorable role in host defense during pneumococcal pneumonia by a mechanism that does not depend on NK cells.

Limited role of kininogen in the host response during gram-negative pneumonia-derived sepsis

High-molecular-weight kininogen (HK), together with factor XI, factor XII and prekallikrein, is part of the contact system that has proinflammatory, prothrombotic, and vasoactive properties. We hypothesized that HK plays a role in the host response during pneumonia-derived sepsis. To this end mice were depleted of kininogen (KNG) to plasma HK levels of 28% of normal by repeated treatment with a specific antisense oligonucleotide (KNG ASO) for 3 wk before infection with the common human sepsis pathogen Klebsiella pneumoniae via the airways. Whereas plasma HK levels increased during infection in mice treated with a scrambled control ASO (Ctrl ASO), HK level in the KNG ASO-treated group remained reduced to 25-30% of that in the corresponding Ctrl ASO group both before and after infection. KNG depletion did not influence bacterial growth in lungs or dissemination to distant body sites. KNG depletion was associated with lower lung CXC chemokine and myeloperoxidase levels but did not impact neutrophil influx, lung pathology, activation of the vascular endothelium, activation of the coagulation system, or the extent of distant organ injury. These results were corroborated by studies in mice with a genetic deficiency of KNG, which were indistinguishable from wild-type mice during Klebsiella-induced sepsis. Both KNG depletion and KNG deficiency were associated with strongly reduced plasma prekallikrein levels, indicating the carrier function of HK for this zymogen. This study suggests that KNG does not significantly contribute to the host defense during gram-negative pneumonia-derived sepsis.

Myocardial injury in critically ill patients with community-acquired pneumonia

Background Myocardial injury, as reflected by elevated cardiac troponin levels in plasma, is common in patients with community-acquired pneumonia (CAP), but its temporal dynamics and etiology remain unknown. Our aim was to determine the incidence of troponin release in patients with CAP and identify risk factors which may point to underlying etiologic mechanisms. Methods We included consecutive patients admitted with severe CAP to two intensive care units in the Netherlands between 2011 and 2015. High-sensitivity cardiac troponin I was measured daily during the first week. We used multivariable linear regression to identify variables associated with troponin release on admission, and mixed-effects regression to model the daily rise and fall of troponin levels over time. Results Among 200 eligible patients, 179 were included, yielding 792 observation days. A total of 152 (85%) patients developed raised troponin levels >26 ng/L. Baseline factors independently associated with troponin release included coronary artery disease (160% increase, 95% CI 7–529), smoking (304% increase, 95% CI 59-924), and higher APACHE IV score (2% increase, 95% CI 0.7-3.3), whereas Staphylococcus aureus as a causative pathogen was protective (67% reduction, 95% CI 9-88). Time-dependent risk factors independently associated with daily increase in troponin concentrations included reduced platelet count (1.7% increase, 95% CI 0.1-3.4), tachycardia (1.6% increase, 95% CI 0.3-3), hypotension (5.1% increase, 95% CI 1-9.4) and dobutamine use (38.4% increase 95% CI 8.8-76). Conclusions Cardiac injury develops in a majority of patients with severe CAP. Myocardial oxygen supply-demand mismatch and activated coagulation are potential causes of this injury.

Cellular and Molecular Aspects of Pneumonia

Immunotherapy aimed at modulation of immune responses may serve as an important adjuvant to antibiotic therapy in the treatment of pneumonia. Alveolar macrophages and polymor-phonuclear cells play a prominent role in innate immunity in the lungs. These cells need to communicate in mounting an effective host defense against invading pathogens. Cytokines, chemokines, and colony-stimulating factors play a critical role in this process. Side-products of the coagulation cascade also enhance local inflammation. Activation of the complement system results in the formation of several proinflammatory mediators that can attract and activate polymorphonuclear cells, and formation of molecules with antimicrobial activity.