Acute community-acquired pneumonia (CAP) is a leading cause of infection-related mortality worldwide. Endotoxemia, characterized by elevated plasma lipopolysaccharide (LPS), is a key driver of inflammation and thrombosis in Gram-negative sepsis and has been suggested to occur in severe pneumonia, irrespective of etiology. However, current immunoassays for LPS quantification lack sensitivity and specificity. We aimed to quantify plasma LPS in severe CAP patients, including COVID-19, using a validated mass spectrometry method, and to explore associations with immune activation, coagulation, gut translocation, and clinical outcomes. In this prospective ancillary study of the LYMPHONIE cohort, we included 34 non-COVID-19 severe CAP (sCAP), 34 severe COVID-19 (sCOVID-19) and 34 matched healthy volunteers. Plasma LPS was measured by LC–MS/MS detecting 3-hydroxy fatty acids of lipid A. Clinical data, immune biomarkers, coagulation biomarkers, and gut injury markers were measured. Unexpectedly, median plasma LPS concentrations were significantly lower in sCAP patients (724 pmol/ml in sCAP; 750 pmol/ml in sCOVID-19) compared to healthy volunteers (1009 pmol/ml, p < 0.001). LPS levels did not correlate with severity scores or mortality. Low positive correlations were observed between LPS and markers of endothelial activation (sVCAM-1) and coagulation (D-dimer). However, patients with high LPS showed no increased risk of thrombotic or cardiovascular events. Using a highly specific LC–MS/MS method, we found no evidence of increased circulating LPS in severe pneumonia patients, challenging the hypothesis of gut-derived endotoxemia as a major contributor to systemic inflammation in severe CAP, including COVID-19. Take-home message Using a highly specific mass-spectrometry assay, we found no evidence of elevated circulating lipopolysaccharide in severe community-acquired pneumonia, including COVID-19. These findings challenge the concept that gut-derived endotoxemia is a major driver of systemic inflammation in severe pneumonia. Tweet Mass spectrometry reveals no rise in plasma LPS in severe pneumonia or COVID-19, questioning gut endotoxemia’s role in inflammation.

Although mesenchymal stromal cells (MSCs) have shown promising effects in preclinical pneumonia models, their ability to improve outcomes in ventilator-associated pneumonia (VAP) remains poorly explored, despite VAP being a frequent and severe complication in critically ill patients. This study investigated whether MSCs could enhance outcomes in a rabbit VAP model. Male rabbits were ventilated and received lipopolysaccharide (LPS, 3 ng/kg) to mimic sepsis-induced immune dysfunction. After 24 h, animals were inoculated intratracheally with Enterobacter aerogenes to induce VAP. In experiment 1, rabbits (n = 10/group) were randomized to receive human umbilical cord-derived MSCs (3 × 10^6/kg, intravenous) or saline, 4 h after bacterial challenge. In experiment 2, all rabbits received cefepime, with or without MSCs. Outcomes included lung bacterial load (primary), systemic dissemination, 24 h survival, lung injury, and markers of immune and mitochondrial dysfunction. MSC infusion alone did not improve survival (8/10 vs. 9/10; p = .46), lung bacterial load (median [IQR] 6.67 [5.64–7.60] vs. 6.08 [5.72–6.82] log10 CFU/ml; p = .37), systemic dissemination, or lung inflammation. Similarly, lung pathology scores, alveolar neutrophils, and systemic cytokines were unaffected. In contrast, when combined with cefepime, MSCs showed a non-significant trend toward improved survival (10/10 vs. 7/10; p = .067), significantly reduced lung bacterial burden (5.23 [5.05–5.56] vs. 5.47 [5.18–7.01] log10 CFU/ml; p = .049), improved macroscopic lung scores (p = .008), and lowered IL-6 levels (p = .037). However, MSCs did not correct systemic immune dysfunction. MSCs alone did not improve lung bacterial clearance or inflammation resolution in this rabbit VAP model. However, the combination of MSCs with cefepime enhanced lung bacterial clearance and reduced lung IL-6 concentrations, compared with cefepime alone. Further studies are required to elucidate the mechanisms underlying the combined effects of antibiotics and MSCs.

Background: Reducing critically ill patients’ exposure to antibiotics is mandatory. In randomized controlled trials, procalcitonin (PCT)-guided algorithms (i.e., antibiotic therapy [ABT] should be stopped whenever PCT is less than 0.5 µg/L or is below 80% of the peak value) reduced the duration of (ABT) more than compliance with the current guidelines. However, the interest of such stopping rules in daily practice remains debated. Thus, we carried out a real-life study addressing this issue. Results: During the study period, 112 patients with sepsis upon intensive care unit admittance were included. The median age was 66 years (56–79). Half of the patients presented with acute respiratory failure. Pneumonia was diagnosed in 78% of them, and 41% met septic shock criteria. The initial ABT was empirical in most cases, and appropriateness rate to the isolated bacteria reached 71%. A median number of four PCT measurements was achieved in both groups. The compliance rate with the PCT algorithm was 54%. The median duration of ABT was 5 (4–7) days if the PCT algorithm was followed, as compared to 7 (5–10) days otherwise (p < 0.001). This ABT stopping rule allowed a 2-day reduction in the treatment duration as compared with those recommended by the guidelines (p < 0.001). The only independent factor associated with shorter treatment duration was compliance with the PCT algorithm (OR = 0.74, 95% CI [0.62; 0.88]; p < 0.001). Regarding safety, no difference in outcome was found between the two groups. Conclusions: Complying with one PCT-based stopping rule is associated with a significant reduction in the duration of ABT in septic critically ill patients, without apparent impact on patient outcomes.

Live-cell imaging generally requires pretreatment with fluorophores to either monitor cellular functions or the dynamics of intracellular processes and structures. We have recently introduced full-field optical coherence tomography for the label-free live-cell imaging of fungi with potential clinical applications for the diagnosis of invasive fungal mold infections. While both the spatial resolution and technical set up of this technology are more likely designed for the histopathological analysis of tissue biopsies, there is to our knowledge no previous work reporting the use of a light interference-based optical technique for direct mycological examination and monitoring of intracellular processes. We describe the first application of dynamic full-field optical transmission tomography (D-FF-OTT) to achieve both high-resolution and live-cell imaging of fungi. First, D-FF-OTT allowed for the precise examination and identification of several elementary structures within a selection of fungal species commonly known to be responsible for invasive fungal infections such as Candida albicans, Aspergillus fumigatus, or Rhizopus arrhizus. Furthermore, D-FF-OTT revealed the intracellular trafficking of organelles and vesicles related to metabolic processes of living fungi, thus opening new perspectives in fast fungal infection diagnostics.

Les biofilms sont des populations ubiquitaires de micro-organismes englobés dans une matrice extracellulaire, susceptibles de se développer sur des surfaces biotiques ou abiotiques, notamment les dispositifs médicaux invasifs, avec le risque à terme de conduire à la survenue d’infections sur matériel. En soins critiques, les cathéters intravasculaires et les sondes d’intubation sont les plus fréquemment associés au développement du biofilm. Pourtant, le rôle de ce dernier dans la survenue d’évènement cliniques infectieux, demeurent incertains. Il n’existe ainsi à ce jour aucune méthode standardisée pour la mise en évidence du biofilm. En particulier, le diagnostic d’infection liée aux dispositifs médicaux invasifs en soins critiques repose aujourd’hui sur un faisceau d’arguments cliniques et microbiologiques qui varient grandement d’une équipe à l’autre. Certaines approches innovantes, comme le recours ponctuel à l’anatomopathologie ou encore à de nouvelles modalités d’imagerie optique, pourraient améliorer la reconnaissance, le diagnostic et le traitement de ces infections. Il s’agirait notamment de mieux orienter le choix de la stratégie thérapeutique parmi le retrait du dispositif impliqué, lorsque cela est possible, ou la place du traitement anti-infectieux le plus adapté à la documentation microbiologique et au risque de germe multirésistant.

IntroductionThe diagnosis of cutaneous manifestations of deep mycoses relies on both histopathological and direct examinations. Yet, the current diagnostic criteria cannot prevent missed cases, including invasive aspergillosis, which requires the development of a novel diagnostic approach and imaging tools. We recently introduced the use of dynamic full-field optical coherence tomography (D-FF-OCT) in fungal diagnostics with a definition approaching that of conventional microscopy and the ability to return metabolic information regarding different fungal species. The present work focuses on subcellular dynamics and live-cell imaging of Aspergillus fumigatus with D-FF-OCT to follow the fungal growth stages.MethodsThe A. fumigatus ATCC 204305 quality-control strain was used for all imaging experiments, following incubation times varying between 24 and 72 h at 30°C in a humidified chamber on Sabouraud dextrose agar. Fungal growth was subsequently monitored with D-FF-OCT for up to 5 h at room temperature and following the pharmacological stress of either voriconazole, amphotericin B, or caspofungin gradient concentration.ResultsD-FF-OCT images allow not only the visualization of intracellular trafficking of vacuoles but also an evolving dynamic segmentation of conidiophores depending on the chronological development and aging of the hyphae or the effect of antifungal treatment. The same applies to conidial heads, with the most intense D-FF-OCT signal coming from vesicles, revealing a changing dynamic within a few hours only, as well as complete extinction following subsequent drying of the Sabouraud dextrose agar.DiscussionThese results provide additional data on the ability of D-FF-OCT to monitor some of the main life cycle processes, dynamics, and intracellular trafficking of vacuoles in A. fumigatus, with or without the effect of pharmacological stress. Such complementary metabolic information could help both clinicians and microbiologists in either mechanistic studies toward experimental mycology or the development of a potential D-FF-OCT-guided diagnosis of superficial fungal infections.

Background: Circulating endotoxins could result from bacterial digestive translocation during sepsis, thus contributing to uncontrolled systemic inflammation, leading in turn to organ dysfunction. We addressed this issue in the setting of severe pneumococcal pneumonia. Methods: Endotoxemia was measured in a clinically relevant rabbit model of ventilated pneumococcal pneumonia and in 110 patients with bacteraemic pneumonia, using a patented mass spectrometry (LC-MS/ MS) method for detection of 3-OH fatty acids (C10, C12, C14, C16 and C18), which are molecules bound to the lipid A motif of LPS. Results: Whereas higher levels of systemic inflammation and organ dysfunctions were found, there was no significant difference in lipopolysaccharide concentrations when infected rabbits were compared to non-infected ones, or when patients were compared to healthy volunteers. Conclusions: Seemingly, endotoxins do not drive the overwhelming inflammation associated with severe forms of pneumococcal pneumonia.

BACKGROUND:While not traditionally included in the conceptual understanding of circulation, the interstitium plays a critical role in maintaining fluid homeostasis. Fluid balance regulation is a critical aspect of septic shock, with a well-known association between fluid balance and outcome. The regulation of transcapillary flow is the first key to understand fluid homeostasis during sepsis.MAIN TEXT:Capillary permeability is increased during sepsis, and was classically considered to be necessary and sufficient to explain the increase of capillary filtration during inflammation. However, on the other side of the endothelial wall, the interstitium may play an even greater role to drive capillary leak. Indeed, the interstitial extracellular matrix forms a complex gel-like structure embedded in a collagen skeleton, and has the ability to directly attract intravascular fluid by decreasing its hydrostatic pressure. Thus, interstitium is not a mere passive reservoir, as was long thought, but is probably major determinant of fluid balance regulation during sepsis. Up to this date though, the role of the interstitium during sepsis and septic shock has been largely overlooked. A comprehensive vision of the interstitium may enlight our understanding of septic shock pathophysiology. Overall, we have identified five potential intersections between septic shock pathophysiology and the interstitium: 1. increase of oedema formation, interacting with organ function and metabolites diffusion; 2. interstitial pressure regulation, increasing transcapillary flow; 3. alteration of the extracellular matrix; 4. interstitial secretion of inflammatory mediators; 5. decrease of lymphatic outflow.CONCLUSIONS:We aimed at reviewing the literature and summarizing the current knowledge along these specific axes, as well as methodological aspects related to interstitium exploration.

Au cours du choc septique, le remplissage vasculaire corrige l’hypovolémie liée à la fuite capillaire, responsable de l’état de choc et de l’apparition progressive d’œdèmes généralisés. La fuite capillaire a longtemps été considérée comme principalement due à des modifications de l’endothélium vasculaire et du glycocalyx. Or, le rôle central du tissu interstitiel dans la régulation des échanges de fluides au cours de l’inflammation est décrit dans un nombre croissant d’études. En effet, la matrice extracellulaire (MEC) interstitielle permet de réguler finement la pression hydrostatique interstitielle par le biais de l’interaction des fibroblastes avec les fibres de collagène de la MEC. Sous l’action des médiateurs pro-inflammatoires lors d’une inflammation localisée, cette tension est relâchée brutalement ce qui entraine une baisse de la pression interstitielle, potentialisant de fait la formation d’œdème. Le rôle de l’interstitium au cours du sepsis est encore très mal connu, mais de nombreuses données semblent indiquer un rôle majeur dans la régulation de la filtration capillaire. L’interstitium a donc probablement un impact significatif dans la régulation de la balance hydrosodée, qui est un des enjeux fondamentaux pour la prise en charge du sepsis.

Abstract Objective Early identification of sepsis is mandatory. However, clinical presentation is sometimes misleading given the lack of infection signs. The objective of the study was to evaluate the impact on the 28-day mortality of the so-called “vague” presentation of sepsis. Design Single centre retrospective observational study. Setting One teaching hospital Intensive Care Unit. Subjects All the patients who presented at the Emergency Department (ED) and were thereafter admitted to the Intensive Care Unit (ICU) with a final diagnosis of sepsis were included in this retrospective observational three-year study. They were classified as having exhibited either “vague” or explicit presentation at the ED according to previously suggested criteria. Baseline characteristics, infection main features and sepsis management were compared. The impact of a vague presentation on 28-day mortality was then evaluated. Interventions None. Measurements and main results Among the 348 included patients, 103 (29.6%) had a vague sepsis presentation. Underlying chronic diseases were more likely in those patients [e.g., peripheral arterial occlusive disease: adjusted odd ratio (aOR) = 2.01, (1.08–3.77) 95% confidence interval (CI); p = 0.028], but organ failure was less likely at the ED [SOFA score value: 4.7 (3.2) vs. 5.2 (3.1), p = 0.09]. In contrast, 28-day mortality was higher in the vague presentation group (40.8% vs. 26.9%, p = 0.011), along with longer time-to-diagnosis [18 (31) vs. 4 (11) h, p < 0.001], time-to-antibiotics [20 (32) vs. 7 (12) h, p < 0.001] and time to ICU admission [71 (159) vs. 24 (69) h, p < 0.001]. Whatever, such a vague presentation independently predicted 28-day mortality [aOR = 2.14 (1.24–3.68) 95% CI; p = 0.006]. Conclusions Almost one third of septic patient requiring ICU had a vague presentation at the ED. Despite an apparent lower level of severity when initially assessed, those patients had an increased risk of mortality that could not be fully explained by delayed diagnosis and management of sepsis.

Histopathology and microscopic examination of infected tissue are the gold standards to prove the diagnosis of invasive fungal infection (IFI). Yet, they suffer from essential limitations that hamper rapid diagnosis and require the future development of new imaging tools dedicated to fungal diagnostics. To this end, the present work introduces the first use of dynamic full-field optical coherence tomography (D-FF-OCT) for the visualization of microscopic filamentous fungi. Data collected from the observation of three different fungal species (Nannizzia gypsea, Aspergillus fumigatus and Rhizopus arrhizus) confirm the ability of D-FF-OCT to visualize not only the main structures of all selected fungal species (hyphae, spores, conidia, sporulating structures), but also the metabolic activity of the organisms, which could provide additional help in the future to better characterize the signature of each fungal structure. These results demonstrate how D-FF-OCT could serve as potential complementary tool for rapid diagnosis of IFI in both intensive and non-intensive care units.

Biofilm (BF) growth is believed to play a major role in the development of ventilator-associated pneumonia (VAP) in the intensive care unit. Despite concerted efforts to understand the potential implication of endotracheal tube (ETT)-BF dispersal, clinically relevant data are lacking to better characterize the impact of its mesostructure and microbiological singularity on the occurrence of VAP. We conducted a multicenter, retrospective observational study during the third wave of the COVID-19 pandemic, between March and May 2021. In total, 64 ETTs collected from 61 patients were included in the present BIOPAVIR study. Confocal microscopy acquisitions revealed two main morphological aspects of ETT-deposited BF: (1) a thin, continuous ribbon-shaped aspect, less likely monobacterial and predominantly associated with Enterobacter spp., Streptococcus pneumoniae or Viridans streptococci, and (2) a thicker, discontinuous, mushroom-shaped appearance, more likely characterized by the association of bacterial and fungal species in respiratory samples. The microbiological characterization of ETT-deposited BF found higher acquired resistance in more than 80% of analyzed BF phenotypes, compared to other colonization sites from the patient’s environment. These findings reveal BF as a singular microbiological compartment, and are of added clinical value, with a view to future ETT-deposited BF-based antimicrobial stewardship in critically ill patients. Trial registration NCT04926493. Retrospectively registered 15 June 2021.

COVID-19 pneumonia has specific features and outcomes that suggests a unique immunopathogenesis. Severe forms of COVID-19 appear to be more frequent in obese patients, but an association with metabolic disorders is not established. Here, we focused on lipoprotein metabolism in patients hospitalized for severe pneumonia, depending on COVID-19 status. Thirty-four non-COVID-19 and 27 COVID-19 patients with severe pneumonia were enrolled. Most of them required intensive care. Plasma lipid levels, lipoprotein metabolism, and clinical and biological (including plasma cytokines) features were assessed. Despite similar initial metabolic comorbidities and respiratory severity, COVID-19 patients displayed a lower acute phase response but higher plasmatic concentrations of non-esterified fatty acids (NEFAs). NEFA profiling was characterised by higher level of polyunsaturated NEFAs (mainly linoleic and arachidonic acids) in COVID-19 patients. Multivariable analysis showed that among severe pneumonia, COVID-19-associated pneumonia was associated with higher NEFAs, lower apolipoprotein E and lower high-density lipoprotein cholesterol concentrations, independently of body mass index, sequential organ failure (SOFA) score, and C-reactive protein levels. NEFAs and PUFAs concentrations were negatively correlated with the number of ventilator-free days. Among hospitalized patients with severe pneumonia, COVID-19 is independently associated with higher NEFAs (mainly linoleic and arachidonic acids) and lower apolipoprotein E and HDL concentrations. These features might act as mediators in COVID-19 pathogenesis and emerge as new therapeutic targets. Further investigations are required to define the role of NEFAs in the pathogenesis and the dysregulated immune response associated with COVID-19. Trial registration: NCT04435223.

The management of acute pancreatitis is now fairly codified, with specific recommendations developed by expert groups. These recommendations deal in particular with the minimum initial assessment, recognized severity scores, initial medical management with hyperhydration, preventive anticoagulation, early refeeding, delays in imaging and management of complications. In this work, we have tried to bring together the various recommendations, articles and studies dealing with this subject, based more particularly on European recommendations, in order to guide the management of acute pancreatitis in current practice.

Rationale: COVID-19 displays distinct characteristics that suggest a unique pathogenesis. The objective of this study was to compare biomarkers of coagulopathy and outcomes in COVID-19 and non-COVID-19 patients with severe pneumonia. Methods: Thirty-six non-COVID-19 and 27 COVID-19 non-immunocompromised patients with severe pneumonia were prospectively enrolled, most requiring intensive care. Clinical and biological characteristics (including plasma biomarkers of coagulopathy) were compared. Results: At similar baseline severity, COVID-19 patients required mechanical ventilation (MV) for significantly longer than non-COVID-19 patients (p = 0.0049) and more frequently developed venous thrombotic complications (p = 0.031). COVID-19 patients had significantly higher plasma concentrations of soluble VCAM1 (sVCAM1) (5,739 ± 3,293 vs. 3,700 ± 2,124 ng/ml; p = 0.009), but lower levels of D-dimers, vWF-A2, sICAM1, sTREM1, VEGF, and P-selectin, compared to non-COVID-19 patients. Principal component analysis identified two main patterns, with a clear distinction between non-COVID-19 and COVID-19 patients. Multivariable regression analysis confirmed that sVCAM1 rising levels were independently associated with a longer duration of MV. Finally, we identified close correlations between sVCAM1 and some features of COVID-19 immune dysregulation (ie. CXCL10, GM-CSF, and IL-10). Conclusion: We identified specific features of the coagulopathy signature in severe COVID-19 patients, with higher plasma sVCAM1 levels, that were independently associated with the longer duration of mechanical ventilation. Clinical Trial Registration:ClinicalTrials.gov, identifier: NCT03505281.

Numerous interventional studies have validated the usefulness of the dosage of procalcitonin for antibiotic stewardship in lower respiratory tract infections (LRTI). Despite the absence of prospective interventional trials specifically for Covid-19 patients, the measurement of procalcitonin can be part of the standard of care in the emergency room as well as in other LRTIs to help with antibiotic decisions. Most non-complicated SARS-CoV-2 infections have procalcitonin concentrations < 0.25 mu g/l. Furthermore, concentrations > 0.5 mu g/l are usually associated with the risk of severe outcome and/or bacterial co-infection. In intensive care units, procalcitonin is promising in patients with acute respiratory distress syndrome due to Covid-19. In those patients, the prescription of antibiotics must be daily reconsidered, in that the risk of bacterial infection is evolving all along the long-lasting duration of stay, in order to limit the selection of resistant strains and limit antibiotic toxicity.

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