Cryopreservation moderates the thrombogenicity of arterial allografts during storage

Introduction Management of vascular infections represents a major challenge in vascular surgery. The use of cryopreserved vascular allografts could be a feasible therapeutic option, but the optimal conditions for their production and use are not precisely defined. Aims To evaluate the effects of cryopreservation and the duration of storage on the thrombogenicity of femoral artery allografts. Methods In our prospective study, eleven multi-organ-donation-harvested human femoral arteries were examined at five time points during storage at -80°C: before cryopreservation as a fresh native sample and immediately, one, twelve and twenty-four weeks after the cryopreservation. Cross-sections of allografts were perfused with heparin-anticoagulated blood at shear-rates relevant to medium-sized arteries. The deposited platelets and fibrin were immunostained. The thrombogenicity of the intima, media and adventitia layers of the artery grafts was assessed quantitatively from the relative area covered by fibrin- and platelet-related fluorescent signal in the confocal micrographs. Results Regression analysis of the fibrin and platelet coverage in the course of the 24-week storage excluded the possibility for increase in the graft thrombogenicity in the course of time and supported the hypothesis for a descending trend in fibrin generation and platelet deposition on the arterial wall. The fibrin deposition in the cryopreserved samples did not exceed the level detected in any of the three layers of the native graft. However, an early (up to week 12) shift above the native sample level was observed in the platelet adhesion to the media. Conclusions The hemostatic potential of cryopreserved arterial allografts was retained, whereas their thrombogenic potential declined during the 6-month storage. The only transient prothrombotic change was observed in the media layer, where the platelet deposition exceeded that of the fresh native grafts in the initial twelve weeks after cryopreservation, suggesting a potential clinical benefit from antiplatelet therapy in this time-window.

Bacteria-host transcriptional response during endothelial invasion by Staphylococcus aureus

Staphylococcus aureus is the cause of serious vascular infections such as sepsis and endocarditis. These infections are notoriously difficult to treat, and it is believed that the ability of S. aureus to invade endothelial cells and persist intracellularly is a key mechanism for persistence despite ongoing antibiotic treatment. Here, we used dual RNA sequencing to study the simultaneous transcriptional response of S. aureus and human endothelial cells during in vitro infections. We revealed discrete and shared differentially expressed genes for both host and pathogen at the different stages of infection. While the endothelial cells upregulated genes involved in interferon signalling and antigen presentation during late infection, S. aureus downregulated toxin expression while upregulating genes related to iron scavenging. In conclusion, the presented data provide an important resource to facilitate functional investigations into host–pathogen interaction during S. aureus invasive infection and a basis for identifying novel drug target sites.

Single Photon Emission Tomography in the Diagnostic Assessment of Cardiac and Vascular Infectious Diseases

Background: Cardiac and vascular infection is a arising cause of mortality and morbidity in the adult population. Diagnosis based on culture and anatomic imaging is frequently inconclusive. Radiolabeled leucocyte scintigraphy plays a useful role in the diagnosis and management of these serious infectious conditions. Objective: In this paper, we present an update on the diagnostic performance of single-photon emission tomographic (SPECT) techniques using different radionuclides in the management of patients with cardiac and vascular infections. Methods: We performed a thorough search of recent literature on the topic. We present a discussion on the clinical utility of different SPECT tracers in cardiac and vascular infections including infective endocarditis, cardiac implantable electronic device (CIED) infections, left ventricular assist device infection, and vascular graft infection. Results: Radionuclide techniques using SPECT tracers is a useful imaging modality in the diagnosis of cardiac infection. Among the different SPECT tracers for infection imaging, radiolabeled leucocytes scintigraphy is currently the most useful tool in the diagnosis and management of patients with suspected cardiac and vascular infection. Radiolabeled leucocytes scintigraphy has a high specificity, a result of the ability of the leucocytes to accumulate as sites of pyogenic infection but not at sites of sterile inflammation such as seen in the early post-operative period or in response to the presence of a prosthetic cardiac or vascular material. Limited experience with radiotracers for in vivo labelling of leucocytes such as 99mTc-sulesomab and 99mTc-besilesomab show acceptable diagnostic performance without the need for the tedious process of ex-vivo labeling. 67Ga scintigraphy used to be popular for cardiac and vascular infection imaging. Its use has run out of favor following the availability of more effective molecular imaging methods. Conclusion: SPECT techniques with radiolabeled leucocytes scintigraphy has a high diagnostic performance in the evaluation of patients with suspected cardiac or vascular infection. It is able to confirm or reject the presence of infection when results of anatomic imaging or culture remain inconclusive. Its diagnostic performance is not compromised by sterile inflammation occurring in the early post-operative period or in response to implanted prosthetic materials.

Neutrophil extracellular traps drive inflammatory pathogenesis in malaria

Neutrophils are essential innate immune cells that extrude chromatin in the form of neutrophil extracellular traps (NETs) when they die. This form of cell death has potent immunostimulatory activity. We show that heme-induced NETs are essential for malaria pathogenesis. Using patient samples and a mouse model, we define two mechanisms of NET-mediated inflammation of the vasculature: activation of emergency granulopoiesis via granulocyte colony-stimulating factor production and induction of the endothelial cytoadhesion receptor intercellular adhesion molecule–1. Soluble NET components facilitate parasite sequestration and mediate tissue destruction. We demonstrate that neutrophils have a key role in malaria immunopathology and propose inhibition of NETs as a treatment strategy in vascular infections.

1029. Outcome of Candida Graft Vascular Infection: Results From a Prospective Cohort

Background Candida graft vascular infections (CGVI) are rare events and little data are available in the literature. The aim of this study was to describe the characteristics and outcome of patients admitted for fungal graft vascular infections, in a reference center for CGVI treatment. Methods Patients admitted for a CGVI in our center from 1 January 2000 to 1 February 2018 were prospectively included. Clinical, biological, and outcome data were recorded. Results Two hundred patients were admitted with graft vascular infections (GVI) in our center, and 11 of them (6%) presented CGVI. They were mainly men (7; 64%), and median age was 74 years old [min–max: 39–83]. All patients had benefited from prosthetic bypass surgery prior to CGVI, and infection was considered as an early disease in six patients (55%). Candida albicans was found in 72% of cases. Infection was plurimicrobial in 10 patients (92%), involving Staphyloccocus aureus in only one case and Bacille gram negatif in six (55%) cases. The management consisted in a total or partial graft replacement for five patients (45%), and surgical revision was required in four of them (30%). The empirical antifungal therapy included an echinocandin (Caspofungine) for eight patients (73%), and was changed to fluconazole or voriconazole according to antifungigram. Two patients received Amphotericin B therapy, complicated by acute kidney injury. Intensive care unit admittance was required for nine patients (82%). After the curative treatment period, antifungal therapy could not be removed in two patients and was long-continued using fluconazole. Finally, six patients (55%) died, all within the year after CGVI. Conclusion To our knowledge, we report here the biggest CGVI cohort. CGVI resulted in very high morbidity and mortality, requiring ICU admission for a long time. Despite multidisciplinary management involving anesthesiologists, surgeons, intensive care, and infectious disease physicians, outcome of CGVI patients remains poor. Disclosures All authors: No reported disclosures.

FluorescenceIn SituHybridization (FISH) and Peptide Nucleic Acid Probe-Based FISH for Diagnosis of Q Fever Endocarditis and Vascular Infections

ABSTRACTEndocarditis and vascular infections are common manifestations of persistent localized infection due toCoxiella burnetii, and recently, fluorescencein situhybridization (FISH) was proposed as an alternative tool for their diagnosis. In this study, we evaluated the efficiency of FISH in a series of valve and vascular samples infected byC. burnetii. We tested 23C. burnetii-positive valves and thrombus samples obtained from patients with Q fever endocarditis. Seven aneurysms and thrombus specimens were retrieved from patients with Q fever vascular infections. Samples were analyzed by culture, immunochemistry, and FISH with oligonucleotide and PNA probes targetingC. burnetii-specific 16S rRNA sequences. The immunohistochemical analysis was positive for five (17%) samples with significantly more copies ofC. burnetiiDNA than the negative ones (P= 0.02). FISH was positive for 13 (43%) samples and presented 43% and 40% sensitivity compared to that for quantitative PCR (qPCR) and culture, respectively. PNA FISH detectedC. burnetiiin 18 (60%) samples and presented 60% and 55% sensitivity compared to that for qPCR and culture, respectively. Immunohistochemistry had 38% and 28% sensitivity compared to that for FISH and PNA FISH, respectively. Samples found positive by both immunohistochemistry and PNA FISH contained significantly more copies ofC. burnetiiDNA than the negative ones (P= 0.03). Finally, PNA FISH was more sensitive than FISH (60% versus 43%, respectively) for the detection ofC. burnetii. We provide evidence that PNA FISH and FISH are important assays for the diagnosis ofC. burnetiiendocarditis and vascular infections.