Objectives Pulmonary thrombus formation is a hallmark of coronavirus disease 2019 (COVID-19). A dysregulated immune response culminating in thromboinflammation has been described, but the pathomechanisms remain unclear.Methods We studied 41 adult COVID-19 patients with positive results on reverse-transcriptase polymerase-chain-reaction assays and 37 sex- and age-matched healthy controls. Number and surface characteristics of extracellular vesicles (EVs) and citrullinated histone H3 levels were determined in plasma upon inclusion by flow cytometry and immunoassay.Results In total, 20 patients had severe and 21 nonsevere disease. The number of EV (median [25th, 75th percentile]) was significantly higher in patients compared with controls (658.8 [353.2, 876.6] vs. 435.5 [332.5, 585.3], geometric mean ratio [95% confidence intervals]: 2.6 [1.9, 3.6]; p < 0.001). Patients exhibited significantly higher numbers of EVs derived from platelets, endothelial cells, leukocytes, or neutrophils than controls. EVs from alveolar-macrophages and alveolar-epithelial cells were detectable in plasma and were significantly higher in patients. Intercellular adhesion molecule-1-positive EV levels were higher in patients, while no difference between tissue factor-positive and angiotensin-converting enzyme-positive EV was seen between both groups. Levels of EV did not differ between patients with severe and nonsevere COVID-19. Citrullinated histone H3 levels (ng/mL, median [25th, 75th percentile]) were higher in patients than in controls (1.42 [0.6, 3.4] vs. 0.31 [0.1, 0.6], geometric mean ratio: 4.44 [2.6, 7.7]; p < 0.001), and were significantly lower in patients with nonsevere disease compared with those with severe disease.Conclusion EV and citrullinated histone H3 are associated with COVID-19 and could provide information regarding pathophysiology of the disease.

Objective and design: SARS-CoV-2 vaccines are recommended for mastocytosis patients. We describe clinical symptoms, chemokine, cytokine, metabolomic and lipidomic derangements in a systemic mastocytosis patient following mRNA-1273 booster vaccination. Methods: Twenty-eight chemokines and cytokines, 41 amino acids and 16 lipid classes were quantified with state-of-the-art methods. Results: Mast cell activation (MCA) symptoms started 24 h after the mRNA-1273 booster vaccination with significant metabolic, lipidomic and cytokine derangements. Histamine concentrations peaked at life-threatening 18 ng/ml concomitant with high tryptase. Peak plasma IL-1Ra, IL-5, IL-6, IL-10, IL-11, CXCL10 and GM-CSF concentrations were elevated 54-, 4.9-, 85-, 54-, 6.1-, 19- and 6.4-fold respectively. Tocilizumab, an IL-6 receptor antagonist, was administered 6 h after admission, because of the highly elevated IL-6 concentrations. More than one year later IL-6 was highly elevated during another MCA attack likely caused by a PCR-proven SARS-CoV-2 infection and tocilizumab was again used. Clinical symptoms improved during the following 12 h similar to the vaccine booster MCA attack. Conclusions: A mRNA-1273 first booster vaccination likely caused a delayed severe MCA attack with highly elevated Th ₂ -biased cytokines with metabolic and lipidomic derangements. Administration of an IL-6 receptor blocker during both MCA attacks might have shortened the duration of clinical symptoms.

Background: Intramuscular adrenaline (epinephrine) is the first‐line treatment for anaphylaxis. This recommendation is based purely on consensus, not randomised controlled trials. In humans, hypotension and shock strongly correlate with plasma histamine concentrations. The efficacy of intramuscular adrenaline in reversing histamine‐induced hypotension remains unproven. This trial evaluated whether intramuscular adrenaline reverses histamine‐induced shock. Methods: We conducted an exploratory open‐label trial and a confirmatory randomised, double‐blind, placebo‐controlled, crossover trial. Healthy volunteers received a 15‐min continuous intravenous histamine infusion to induce hypotension. At 5 min, participants received either intramuscular adrenaline (300–500 μg) or placebo. A second adrenaline dose was administered if the mean arterial pressure (MAP) remained below 60 mmHg at 10 min. The primary endpoint was area under the effect curve for change in MAP. Results: During histamine‐induced hypotension, intramuscular adrenaline failed to produce a pressor response and was indistinguishable from placebo in the majority of participants. Excluding two subjects who needed a simultaneous dose reduction of histamine, only 5 of 20 participants (25%; 95% CI 8.7%–49.1%) demonstrated a transient MAP recovery after a single dose. A second adrenaline dose administered to participants who did not reach a MAP > 60 mmHg also failed to reverse hypotension. The primary outcome in the confirmatory cohort, excluding two subjects with histamine dose adjustments, was not different between treatments (adrenaline‐placebo: 7 mmHg·min, 95% CI −2 to 25; p = 0.06). Conclusion: In this study of a limited number of healthy human subjects, intramuscular adrenaline injections did not provide a sustained response in severe histamine‐mediated hypotension in a majority of recipients. Trial Registration: CTIS (2022–003591‐16) and ISRCTN (Nr. 11335622; https://doi.org/10.1186/ISRCTN11335622 )

Personal protective equipment and adherence to disinfection protocols are essential to prevent nosocomial severe acute respiratory syndrome coronavirus (SARS-CoV-2) transmission. Here, we evaluated infection control measures in a prospective longitudinal single-center study at the Vienna General Hospital, the biggest tertiary care center in Austria, with a structurally planned low SARS-CoV-2 exposure. SARS-CoV-2-specific antibodies were assessed by Abbott ARCHITECT chemiluminescent assay (CLIA) in 599 health care workers (HCWs) at the start of the SARS-CoV-2 epidemic in early April and two months later. Neutralization assay confirmed CLIA-positive samples. A structured questionnaire was completed at both visits assessing demographic parameters, family situation, travel history, occupational coronavirus disease 2019 (COVID-19) exposure, and personal protective equipment handling. At the first visit, 6 of 599 participants (1%) tested positive for SARS-CoV-2-specific antibodies. The seroprevalence increased to 1.5% (8/553) at the second visit and did not differ depending on the working environment. Unprotected SARS-CoV-2 exposure (p = 0.003), positively tested family members (p = 0.04), and travel history (p = 0.09) were more frequently reported by positively tested HCWs. Odds for COVID-19 related symptoms were highest for congestion or runny nose (p = 0.002) and altered taste or smell (p < 0.001). In conclusion, prevention strategies proved feasible in reducing the risk of transmission of SARS-CoV-2 from patients and among HCWs in a low incidence hospital, not exceeding the one described in the general population.

Peritonitis remains the major infectious complication in the setting of peritoneal dialysis (PD). Despite known only moderate pathogenicity, the most frequently detected pathogens in PD-related peritonitis are surprisingly coagulase-negative staphylococci. However, this could be explained, at least in part, by Staphylococcus aureus small colony variants (SCVs) induced by PD fluids (PDFs) and misidentified by routinely used microbiological methods. Bacteria were exposed to commonly used PDFs in various regimens designed to simulate daily use as closely as possible. Wild-type isolates and SCVs were subsequently used to determine minimum inhibitory concentrations (MICs), in vitro biofilm formation capacities, and auxotrophies. Underlying genetic alterations were investigated using whole-genome sequencing, and various microbial identification methods were tested to determine their performance for wild-types and SCVs. Stable SCVs could be isolated most successfully after exposure to glucose-containing PDFs alone. The reading of MICs was significantly affected by the reduced growth of SCVs, resulting in lower MIC values in 44% of all tests. Nonsynonymous mutations were found in all but one SCV, while only two isolates showed typical auxotrophic responses. While MALDI-TOF, PCR and Pastorex Staph-Plus correctly identified all S. aureus SCVs, API-Staph and VITEK-2 yielded identification rates of only 40% and 10%, respectively. Overall, the present study has shown that commercially available PDFs induce S. aureus SCVs in vitro, which are difficult to identify and test for antimicrobial susceptibility and can potentially lead to recurrent or persistent infections. Thus, they represent a potentially underappreciated challenge not only for microbiologists, but also for clinicians.