Long-term comprehensive cardiopulmonary phenotyping of COVID-19.

BACKGROUND: Persistent symptoms after initial COVID-19 infection are common and are frequently referred to by the umbrella terms "post-COVID syndrome" and "long COVID". The sheer number of affected patients pose an increasing challenge to healthcare systems worldwide. To date, our understanding of the pathophysiology of the post-COVID syndrome remains poor and the extent to which persistent cardiopulmonary abnormalities contribute to the symptom complex is unclear. We sought to determine the presence and impact of cardiopulmonary sequelae after COVID-19 in longitudinal assessment. METHODS: We report on 71 patients who underwent comprehensive, longitudinal testing in regular intervals for up to 12 months after their initial COVID-19 diagnosis. Testing included pulmonary function testing, cardiopulmonary exercise testing, dedicated left and right heart echocardiography, lung ultrasonography, and cardiac MRI. RESULTS: Our results demonstrate that subjective quality of life after COVID-19 (EQ-5D visual acuity scale, VAS, 67.4 for patients treated as outpatient, 79.2 for patients admitted to the general floor, 71.8 for patients treated in an ICU) is not related to the severity of the initial infection. Maximal exercise capacity is also reduced (VO2max 79% predicted, SD ± 19%); however, this is driven in large parts by patients who had initially required ICU-level of care. The degree of objective reduction in exertion did not correlate with quality of life scores. Pulmonary function testing revealed mild and persistent reduction in DLCO over the first 12 months without significant restrictive or obstructive lung disease. Left and right heart function was intact with good RV function and intact RV/PA coupling, imaging findings suggestive of myocarditis were uncommon (7% of patients). CONCLUSION: A reduction in exercise capacity after COVID-19 is common, but is most prominent in patients previously treated in the ICU and more likely related to deconditioning or fatigue than to cardiopulmonary impairment. Subjective quality of life scores are independent of the severity of initial infection and do not correlate with objective measures of cardiopulmonary function. In our cohort, persistent cardiopulmonary impairment after COVID-19 was uncommon. The post-COVID syndrome is unlikely to be the result of cardiopulmonary sequalae and may reflect a post-ICU syndrome in some. Trial registration Registered on clinicaltrials.gov (NCT04442789), Date: June 23, 2020.

Infection in a Young Immunocompetent Male Caused by Streptobacillus felis, a Putative Zoonotic Microorganism Transmitted by Cats.

Rat bite fever (RBF) is predominantly caused by Streptobacillus moniliformis. We report a human infection with Streptobacillus felis. Clinical presentation was consistent with RBF, but serologic testing was negative for S moniliformis. Eventually, S felis-specific sequences were detected in skin lesions of the patient and in the oropharynx of local cats.

Nonstable Staphylococcus aureus Small-Colony Variants Are Induced by Low pH and Sensitized to Antimicrobial Therapy by Phagolysosomal Alkalinization.

BACKGROUND: Staphylococcus aureus-infected patients treated with antibiotics that are effective in vitro often experience relapse of infection because the bacteria hide in privileged locations. These locations include abscesses and host cells, which contain low-pH compartments and are sites from which nonstable S. aureus small-colony variants (SCVs) are frequently recovered. METHODS: We assessed the effect of low pH on S. aureus colony phenotype and bacterial growth, using in vitro and in vivo models of long-term infection. RESULTS: We showed that low pH induced nonstable SCVs and nonreplicating persisters that are capable of regrowth. Within host cells, S. aureus was located in phagolysosomes, a low-pH compartment. Therapeutic neutralization of phagolysosomal pH with ammonium chloride, bafilomycin A1, or the antimalaria drug chloroquine reduced SCVs in infected host cells. In a systemic mouse infection model, treatment with chloroquine also reduced SCVs. CONCLUSIONS: Our results show that the acidic environment favors formation of nonstable SCVs, which reflect the SCVs found in clinics. They also provide evidence that treatment with alkalinizing agents, together with antibiotics, may provide a novel translational strategy for eradicating persisting intracellular reservoirs of staphylococci. This approach may also be extended to other intracellular bacteria.

Accumulating evidence for a role of oxidized phospholipids in infectious diseases.

Oxidized phospholipids (OxPL) were originally discovered as by-products and mediators of chronic inflammation such as in atherosclerosis. Over the last years, an increasing body of evidence led to the notion that OxPL not only contribute to the pathogenesis of chronic inflammatory processes but in addition play an integral role as modulators of inflammation during acute infections. Thereby, host defense mechanisms involve the generation of oxygen radicals that oxidize ubiquitously present phospholipids, which in turn act as danger-associated molecular patterns (DAMPs). These OxPL-derived DAMPs can exhibit both pro- and anti-inflammatory functions that ultimately alter the host response to pathogens. In this review, we summarize the currently available data on the role of OxPL in infectious diseases.

The scavenger receptor CD36 downmodulates the early inflammatory response while enhancing bacterial phagocytosis during pneumococcal pneumonia.

CD36 is a scavenger receptor that exhibits pleiotropic functions, including adhesion to thrombospondin, inhibition of angiogenesis, transport of long-chain fatty acids, and clearance of apoptotic cells. In addition, it has been implicated in the host immune response because it acts as a coreceptor for TLR2 and plays a role in Staphylococcus aureus infection. However, its role in other Gram-positive bacterial infections is unclear. In this study, using mice deficient in CD36, we sought to examine the role of CD36 in pneumococcal pneumonia, a major cause of morbidity and mortality worldwide. We show that CD36 is expressed on both alveolar macrophages and respiratory epithelial cells. Early in infection, CD36(-/-) mice have an exaggerated inflammatory response compared with wild-type littermate controls. In vitro studies using CD36(-/-) primary cells confirm the enhanced early inflammation in response to S. pneumoniae and its lipoteichoic acid, demonstrate that S. pneumoniae binds to cells via its phosphocholine residues, and suggest a role for CD36 in reducing inflammation induced by the phosphocholine residues of pneumococcal lipoteichoic acid. Later in infection, although CD36(-/-) mice exhibit impaired bacterial clearance, owing to a decreased capacity of CD36(-/-) macrophages to phagocytose S. pneumoniae, minor effects on mortality occur, in comparison with those in wild-type littermate control mice. These data show that CD36 contributes to the pulmonary host response during S. pneumoniae infection by virtue of its ability to act as a phagocytic receptor and as a modulator of the early innate immune response.

USA300 methicillin-resistant Staphylococcus aureus in Zurich, Switzerland between 2001 and 2013.

USA300 methicillin-resistant Staphylococcus aureus (MRSA) is the most prevalent MRSA in the United States of America (USA) and a global epidemic threat. We investigated the prevalence of USA300 at a tertiary care hospital in Zurich, Switzerland, where all MRSA strains have been collected and PFGE typed since 1992. These strains were retrospectively compared to the PFGE pattern of USA300 strain JE2. Isolates with a respective PFGE pattern were spa-typed and tested for the presence of the arginine catabolic mobile element (ACME) arc gene cluster and Panton-Valentine Leucocidin (PVL) genes. The first MRSA strain with a USA300 PFGE pattern was isolated in 2001 from a patient visiting from the USA. USA300 strains represented between 0% (in 2002) and 9.2% (in 2012) of all MRSA isolates in our hospital. We identified various USA300 subtypes based on either the PFGE pattern, the spa-type or absence of either the PVL genes or ACME arc gene cluster. All the USA300 strains including the variants (n=47) accounted for 5.6% of all MRSA isolates typed between 2001 and 2013 and reached a maximum of 14.5% in 2009. They predominantly caused skin and soft tissue infections (74.4%). In conclusion, even though USA300 has been present in our hospital for over twelve years it has not become the predominant MRSA clone like in the USA. However, in light of the global burden of USA300, care must be taken to further contain the spread of this lineage and of MRSA in general in our hospital.

The guardians of pulmonary harmony: alveolar macrophages orchestrating the symphony of lung inflammation and tissue homeostasis.

Recent breakthroughs in single-cell sequencing, advancements in cellular and tissue imaging techniques, innovations in cell lineage tracing, and insights into the epigenome collectively illuminate the enigmatic landscape of alveolar macrophages in the lung under homeostasis and disease conditions. Our current knowledge reveals the cellular and functional diversity of alveolar macrophages within the respiratory system, emphasising their remarkable adaptability. By synthesising insights from classical cell and developmental biology studies, we provide a comprehensive perspective on alveolar macrophage functional plasticity. This includes an examination of their ontology-related features, their role in maintaining tissue homeostasis under steady-state conditions and the distinct contribution of bone marrow-derived macrophages (BMDMs) in promoting tissue regeneration and restoring respiratory system homeostasis in response to injuries. Elucidating the signalling pathways within inflammatory conditions, the impact of various triggers on tissue-resident alveolar macrophages (TR-AMs), as well as the recruitment and polarisation of macrophages originating from the bone marrow, presents an opportunity to propose innovative therapeutic approaches aimed at modulating the equilibrium between phenotypes to induce programmes associated with a pro-regenerative or homeostasis phenotype of BMDMs or TR-AMs. This, in turn, can lead to the amelioration of disease outcomes and the attenuation of detrimental inflammation. This review comprehensively addresses the pivotal role of macrophages in the orchestration of inflammation and resolution phases after lung injury, as well as ageing-related shifts and the influence of clonal haematopoiesis of indeterminate potential mutations on alveolar macrophages, exploring altered signalling pathways and transcriptional profiles, with implications for respiratory homeostasis.

Nucleated red blood cells are a late biomarker in predicting intensive care unit mortality in patients with COVID-19 acute respiratory distress syndrome: an observational cohort study.

Background: Nucleated red blood cells (nRBC) are precursor cells of the erythropoiesis that are absent from the peripheral blood under physiological conditions. Their presence is associated with adverse outcomes in critically ill patients. This study aimed to evaluate the predictive value of nRBC on mortality in intensive care unit (ICU) patients with COVID-19 acute respiratory distress syndrome (ARDS). Material and methods: This retrospective, observational cohort study analyzed data on 206 ICU patients diagnosed with COVID-19 ARDS between March 2020 and March 2022. The primary endpoint was ICU mortality, and secondary endpoints included ICU and hospital stay lengths, ventilation hours, and the time courses of disease severity scores and clinical and laboratory parameters. Results: Among the included patients, 68.9% tested positive for nRBC at least once during their ICU stay. A maximum nRBC of 105 µl-1 had the highest accuracy in predicting ICU mortality (area under the curve of the receiver operating characteristic [AUCROC] 0.780, p < 0.001, sensitivity 69.0%, specificity 75.5%). Mortality was significantly higher among patients with nRBC >105 µl-1 than ≤105 µl-1 (86.5% vs. 51.3%, p = 0.008). Compared to patients negative for nRBC in their peripheral blood, those positive for nRBC required longer mechanical ventilation (127 [44 - 289] h vs. 517 [255 - 950] h, p < 0.001), ICU stays (12 [8 - 19] vs. 27 [13 - 51] d, p < 0.001), and hospital stays (19 [12 - 29] d vs. 31 [16 - 58] d, p < 0.001). Peak Sepsis-related Organ Failure Assessment (SOFA), Simplified Acute Physiology Score, PaO2/FiO2, interleukin-6, and procalcitonin values were reached before the peak nRBC level. However, the predictive performance of the SOFA (AUCROC 0.842, p < 0.001) was considerably improved when a maximum SOFA score >8 and nRBC >105 µl-1 were combined. Discussion: nRBC predict ICU mortality and indicate disease severity among patients with COVID-19 ARDS, and they should be considered a clinical alarm signal for a worse outcome. nRBC are a late predictor of ICU mortality compared to other established clinical scoring systems and laboratory parameters but improve the prediction accuracy when combined with the SOFA score.

Type I interferon production induced by Streptococcus pyogenes-derived nucleic acids is required for host protection.

Streptococcus pyogenes is a Gram-positive human pathogen that is recognized by yet unknown pattern recognition receptors (PRRs). Engagement of these receptor molecules during infection with S. pyogenes, a largely extracellular bacterium with limited capacity for intracellular survival, causes innate immune cells to produce inflammatory mediators such as TNF, but also type I interferon (IFN). Here we show that signaling elicited by type I IFNs is required for successful defense of mice against lethal subcutaneous cellulitis caused by S. pyogenes. Type I IFN signaling was accompanied with reduced neutrophil recruitment to the site of infection. Mechanistic analysis revealed that macrophages and conventional dendritic cells (cDCs) employ different signaling pathways leading to IFN-beta production. Macrophages required IRF3, STING, TBK1 and partially MyD88, whereas in cDCs the IFN-beta production was fully dependent on IRF5 and MyD88. Furthermore, IFN-beta production by macrophages was dependent on the endosomal delivery of streptococcal DNA, while in cDCs streptococcal RNA was identified as the IFN-beta inducer. Despite a role of MyD88 in both cell types, the known IFN-inducing TLRs were individually not required for generation of the IFN-beta response. These results demonstrate that the innate immune system employs several strategies to efficiently recognize S. pyogenes, a pathogenic bacterium that succeeded in avoiding recognition by the standard arsenal of TLRs.

Blind spot in endocarditis guidelines: Mycobacterium chimaera prosthetic valve endocarditis after cardiac surgery-a case series.

Background: The recently published 2023 Duke-ISCVID Criteria for Infective Endocarditis for the first time consider mycobacteria (esp. Mycobacterium chimaera) as 'typical' microorganisms for prosthetic valve endocarditis (major criteria). This reflects the ongoing worldwide outbreak of M. chimaera prosthetic valve endocarditis. Case summary: Our case series demonstrates a diagnostic pathway for mycobacterial endocarditis. Symptoms are unspecific, and standard microbiological testing does not result in identification of the causative agent (see Graphical Abstract); therefore patients require special microbiological and imaging diagnostics. One patient with early diagnosis and stringent antibiotic and surgical therapy survived. Two patients with disseminated infection at the time point of diagnosis had fatal outcomes. Discussion: The diagnostic approach in our small retrospective case series is in line with the new modified Duke criteria and underlines the diagnostic gap in the previous definitions. Outcome of M. chimaera prosthetic valve endocarditis is related to timely diagnosis and anti-mycobacterial as well as surgical treatment. Non-tuberculous mycobacteria should be given more attention in future endocarditis guidelines.

Alveolar macrophages in tissue homeostasis, inflammation, and infection: evolving concepts of therapeutic targeting.

Alveolar macrophages (AMs) are the sentinel cells of the alveolar space, maintaining homeostasis, fending off pathogens, and controlling lung inflammation. During acute lung injury, AMs orchestrate the initiation and resolution of inflammation in order to ultimately restore homeostasis. This central role in acute lung inflammation makes AMs attractive targets for therapeutic interventions. Single-cell RNA-Seq and spatial omics approaches, together with methodological advances such as the generation of human macrophages from pluripotent stem cells, have increased understanding of the ontogeny, function, and plasticity of AMs during infectious and sterile lung inflammation, which could move the field closer to clinical application. However, proresolution phenotypes might conflict with proinflammatory and antibacterial responses. Therefore, therapeutic targeting of AMs at vulnerable time points over the course of infectious lung injury might harbor the risk of serious side effects, such as loss of antibacterial host defense capacity. Thus, the identification of key signaling hubs that determine functional fate decisions in AMs is of the utmost importance to harness their therapeutic potential.

Myeloid PTEN promotes inflammation but impairs bactericidal activities during murine pneumococcal pneumonia.

Phosphatidylinositol 3-kinase has been described as an essential signaling component involved in the chemotactic cell influx that is required to eliminate pathogens. At the same time, PI3K was reported to modulate the immune response, thus limiting the magnitude of acute inflammation. The precise role of the PI3K pathway and its endogenous antagonist phosphatase and tensin homolog deleted on chromosome 10 (PTEN) during clinically relevant bacterial infections is still poorly understood. Utilizing mice lacking myeloid cell-specific PTEN, we studied the impact of PTEN on the immune response to Streptococcus pneumoniae. Survival analysis disclosed that PTEN-deficient mice displayed less severe signs of disease and prolonged survival. The inflammatory response to S. pneumoniae was greatly reduced in macrophages in vitro and in vivo. Unexpectedly, neutrophil influx to the lungs was significantly impaired in animals lacking myeloid-cell PTEN, whereas the additional observation of improved phagocytosis by alveolar macrophages lacking PTEN ultimately resulted in unaltered lung CFUs following bacterial infection. Together, the absence of myeloid cell-associated PTEN and consecutively enhanced PI3K activity dampened pulmonary inflammation, reduced neutrophil influx, and augmented phagocytic properties of macrophages, which ultimately resulted in decreased tissue injury and improved survival during murine pneumococcal pneumonia.

TREM-1 activation alters the dynamics of pulmonary IRAK-M expression in vivo and improves host defense during pneumococcal pneumonia.

Triggering receptor expressed on myeloid cells-1 (TREM-1) is an amplifier of TLR-mediated inflammation during bacterial infections. Thus far, TREM-1 is primarily associated with unwanted signs of overwhelming inflammation, rendering it an attractive target for conditions such as sepsis. Respiratory tract infections are the leading cause of sepsis, but the biological role of TREM-1 therein is poorly understood. To determine the function of TREM-1 in pneumococcal pneumonia, we first established TREM-1 up-regulation in infected lungs and human plasma together with augmented alveolar macrophage responsiveness toward Streptococcus pneumoniae. Mice treated with an agonistic TREM-1 Ab and infected with S. pneumoniae exhibited an enhanced early induction of the inflammatory response that was indirectly associated with lower levels of negative regulators of TLR signaling in lung tissue in vivo. Later in infection, TREM-1 engagement altered S. pneumoniae-induced IRAK-M (IL-1R-associated kinase-M) kinetics so as to promote the resolution of pneumonia and remarkably led to an accelerated elimination of bacteria and consequently improved survival. These data show that TREM-1 exerts a protective role in the innate immune response to a common bacterial infection and suggest that caution should be exerted in modulating TREM-1 activity during certain clinically relevant bacterial infections.

Bbeta(15-42) protects against acid-induced acute lung injury and secondary pseudomonas pneumonia in vivo.

RATIONALE: Acute lung injury (ALI) is a serious condition in critically ill patients that predisposes to secondary bacterial pneumonia. Vascular leak is a hallmark in the pathogenesis of ALI. The fibrin-derived peptide Bbeta(15-42) was shown to preserve endothelial barriers, thereby reducing vascular leak. The potential therapeutic role of Bbeta(15-42) in ALI has not been addressed so far. OBJECTIVES: To investigate the therapeutic potential of Bbeta(15-42) in ALI and secondary pneumonia induced by Pseudomonas aeruginosa. METHODS: The effect of the fibrin-derived peptide Bbeta(15-42) was studied in models of ALI, induced either by pulmonary administration of LPS or hydrochloric acid. Lung inflammation was analyzed by quantifying cell influx, cytokine levels, and oxidized lipids. Vascular leak was determined by Evans Blue extravasations and alveolar protein content. In subsequent two-hit studies, mice were infected with P. aeruginosa 24 hours after induction of aspiration pneumonitis and effects of Bbeta(15-42) on inflammation, bacterial clearance, and survival were evaluated. MEASUREMENTS AND MAIN RESULTS: After LPS or acid inhalation, proinflammatory cytokine levels, neutrophil influx, and vascular leak were found diminished in mice treated with Bbeta(15-42). Acid aspiration impaired macrophage functions and rendered mice more susceptible to subsequent P. aeruginosa infection, whereas mice that received Bbeta(15-42) during acid aspiration and were subsequently challenged with bacteria displayed reduced inflammation, enhanced bacterial clearance, and ultimately improved survival. CONCLUSIONS: The fibrin-derived peptide Bbeta(15-42) exerted protective effects during ALI, resulting in diminished lung injury and preserved antibacterial properties of macrophages, which improved outcome during subsequent P. aeruginosa pneumonia.

Characterisation of clinical manifestations and treatment strategies for invasive beta-haemolytic streptococcal infections in a Swiss tertiary hospital.

AIMS OF THE STUDY: Invasive streptococcal infections affect more than half a million patients worldwide every year and have a high lethality. Little is known about the epidemiology and microbiological characteristics of streptococcal infections in Switzerland. This case series study aims to describe the demographics, known risk factors for streptococcal skin and soft tissue infections, clinical presentations, treatment and outcomes of patients admitted to the University Hospital Zurich between 2000 and 2014 with invasive streptococcal infections caused by Streptococcus pyogenes (group A Streptococcus), Streptococcus dysgalactiae ssp. equisimilis or the Streptococcus anginosus group, as well as the microbiological characteristics of the clinical isolates. METHODS: Data collected retrospectively from patients hospitalised between 2000 and 2014 with invasive streptococcal infections were analysed. M protein gene (emm) typing of the bacterial clinical isolates was carried out according to the Centers for Disease Control and Prevention guidelines. RESULTS: A total of 86 patients with invasive beta-haemolytic streptococcal infections were included in this study, of which 49% presented with necrotising fasciitis (NF). The median age was 44 years and half were female. The most common risk factor was acute skin lesions. C-reactive protein levels were significantly higher in patients with NF, as were acute renal failure and distributive shock. Beta-lactam antibiotics were given to most patients, and intravenous immunoglobulins were given to 18% of patients within the first 24 hours. All patients suffering from NF underwent surgery. The overall case fatality rate was 8.1% at 30 days post admission. All Group A Streptococcus strains were susceptible to penicillin and clindamycin, and we found resistance to tetracycline in 11.9% of strains. The most common emm-type isolated was emm1 (44.4%). CONCLUSIONS: Invasive beta-haemolytic streptococcal infections, the most severe presentation of which is NF, remain a serious clinical issue and require rapid diagnosis and treatment. This is the first representative analysis monitoring clinical and microbiological characteristics of patients with a severe invasive beta-haemolytic streptococcal infection and treated in Zurich, Switzerland. In addition to the detailed reporting of various clinical and microbiological characteristics, we show that C-reactive protein levels, acute renal failure and distributive shock were higher in the patients with NF. We also found a low case fatality rate compared to other reports. The detailed clinical data and microbiological characteristics depicted in this study will lead to a better understanding of regional differences in severe invasive streptococcal infections.