Aspirin Effect on Staphylococcus aureus-Platelet Interactions During Infectious Endocarditis

Universal receptive system as a novel regulator of transcriptomic activity of Staphylococcus aureus

Our previous studies revealed the existence of a Universal Receptive System that regulates interactions between cells and their environment. This system is composed of DNA- and RNA-based Teazeled receptors (TezRs) found on the surface of prokaryotic and eukaryotic cells, as well as integrases and recombinases. In the current study, we aimed to provide further insight into the regulatory role of TezR and its loss in Staphylococcus aureus gene transcription. To this end, transcriptomic analysis of S. aureus MSSA VT209 was performed following the destruction of TezRs. Bacterial RNA samples were extracted from nuclease-treated and untreated S. aureus MSSA VT209. After destruction of the DNA-based-, RNA-, or combined DNA- and RNA-based TezRs of S. aureus, 103, 150, and 93 genes were significantly differently expressed, respectively. The analysis revealed differential clustering of gene expression following the loss of different TezRs, highlighting individual cellular responses following the loss of DNA- and RNA-based TezRs. KEGG pathway gene enrichment analysis revealed that the most upregulated pathways following TezR inactivation included those related to energy metabolism, cell wall metabolism, and secretion systems. Some of the genetic pathways were related to the inhibition of biofilm formation and increased antibiotic resistance, and we confirmed this at the phenotypic level using in vitro studies. The results of this study add another line of evidence that the Universal Receptive System plays an important role in cell regulation, including cell responses to the environmental factors of clinically important pathogens, and that nucleic acid-based TezRs are functionally active parts of the extrabiome.

Universal Receptive System as a novel regulator of transcriptomic activity of Staphylococcus aureus

Our previous studies revealed the existence of a Universal Receptive System that regulates interactions between cells and their environment. This system is composed of DNA- and RNA-based Teazeled receptors (TezRs) found on the surface of prokaryotic and eukaryotic cells, as well as integrases and recombinases.. In the current study, we aimed to provide further insight into the regulatory role of TezR and its loss in Staphylococcus aureus gene transcription. To this end, transcriptomic analysis of S. aureus MSSA VT209 was performed following the destruction of TezRs. Bacterial RNA samples were extracted from nuclease-treated and untreated S. aureus MSSA VT209. After destruction of the DNA-based-, RNA-, or combined DNA- and RNA-based TezRs of S. aureus , 103, 150, and 93 genes were significantly differently expressed, respectively. The analysis revealed differential clustering of gene expression following the loss of different TezRs, highlighting individual cellular responses following the loss of DNA- and RNA-based TezRs. KEGG pathway gene enrichment analysis revealed that the most upregulated pathways following TezR inactivation included those related to energy metabolism, cell wall metabolism, and secretion systems. Some of the genetic pathways were related to the inhibition of biofilm formation and increased antibiotic resistance, and we confirmed this at the phenotypic level using in vitro studies. The results of this study add another line of evidence that the Universal Receptive System plays an important role in cell regulation, including cell responses to the environmental factors of clinically important pathogens, and that nucleic acid-based TezRs are functionally active parts of the extrabiome.

Current Knowledge of Enterococcal Endocarditis: A Disease Lurking in Plain Sight of Health Providers

Enterococcus faecalis is a bacterial pathogen that can cause opportunistic infections. Studies indicate that initial biofilm formation plays a crucial regulatory role in these infections, as well as in colonising and maintaining the gastrointestinal tract as a commensal member of the microbiome of most land animals. It has long been thought that vegetation of endocarditis resulting from bacterial attachment to the endocardial endothelium requires some pre-existing tissue damage, and in animal models of experimental endocarditis, mechanical valve damage is typically induced by cardiac catheterisation preceding infection. This section reviews historical and contemporary animal model studies that demonstrate the ability of E. faecalis to colonise the undamaged endovascular endothelial surface directly and produce robust microcolony biofilms encapsulated within a bacterially derived extracellular matrix. This report reviews both previous and current animal model studies demonstrating the resilient capacity of E. faecalis to colonise the undamaged endovascular endothelial surface directly and produce robust microcolony biofilms encapsulated in a bacterially derived extracellular matrix. The article also considers the morphological similarities when these biofilms develop on different host sites, such as when E. faecalis colonises the gastrointestinal epithelium as a commensal member of the common vertebrate microbiome, lurking in plain sight and transmitting systemic infection. These phenotypes may enable the organism to survive as an unrecognised infection in asymptomatic subjects, providing an infectious resource for subsequent clinical process of endocarditis.

Antithrombotic Therapy in Patients With Infective Endocarditis: A Systematic Review and Meta-Analysis

Background

Antithrombotic therapy (ATT) in patients with infective endocarditis (IE) is challenging.

Objectives

The authors evaluated the impact of anticoagulant and antiplatelet therapy on clinical endpoints in IE patients.

Methods

We performed a systematic review and meta-analysis comparing IE patients with prior and/or ongoing use of ATT vs those without any ATT during IE course. Primary outcome was reported in-hospital cerebrovascular events. Secondary outcomes were in-hospital mortality, intracranial hemorrhage (ICH), systemic thromboembolism (ST), and mortality within 6 months.

Results

Twelve studies, with a total of 12,151 patients, were included. The primary endpoint was not different comparing 10,115 IE patients with or without prior anticoagulation (OR: 1.10; 95% CI: 0.56-2.17; P = 0.77) or comparing 838 IE patients with or without prior antiplatelet (OR: 0.90; 95% CI: 0.61-1.33; P = 0.61). In-hospital mortality was lower in IE patients with prior anticoagulation compared to those without (OR: 0.74; 95% CI: 0.57-0.96; P = 0.03). There was no difference in reported ICH rates between patients with or without prior anticoagulation (OR: 0.54; 95% CI: 0.27-1.09; P = 0.09) or between patients with or without prior antiplatelet (OR: 0.35; 95% CI: 0.11-1.10; P = 0.07). The rate of ST was lower in IE patients with prior antiplatelet therapy compared to those without (OR: 0.53; 95% CI: 0.38-0.72; P < 0.01).

Conclusions

ATT in IE patients was not associated with higher frequency of cerebrovascular events or ICH. Moreover, we found that the use of anticoagulation was associated with decreased in-hospital mortality and the use of antiplatelets was associated with decreased ST. Due to the limitations of this study, these results should be interpreted cautiously showing the necessity of a randomized setup.

Diflunisal and Analogue Pharmacophores Mediating Suppression of Virulence Phenotypes in Staphylococcus aureus

Invasive methicillin-resistant Staphylococcus aureus (MRSA) infections are leading causes of morbidity and mortality that are complicated by increasing resistance to conventional antibiotics. Thus, minimizing virulence and enhancing antibiotic efficacy against MRSA is a public health imperative. We originally demonstrated that diflunisal (DIF; [2-hydroxy-5-(2,4-difluorophenyl) benzoic acid]) inhibits S. aureus virulence factor expression. To investigate pharmacophores that are active in this function, we evaluated a library of structural analogues for their efficacy to modulate virulence phenotypes in a panel of clinically relevant S. aureus isolates in vitro. Overall, the positions of the phenyl, hydroxyl, and carboxylic moieties and the presence or type of halogen (F vs. Cl) influenced the efficacy of compounds in suppressing hemolysis, proteolysis, and biofilm virulence phenotypes. Analogues lacking halogens inhibited proteolysis to an extent similar to DIF but were ineffective at reducing hemolysis or biofilm production. In contrast, most analogues lacking the hydroxyl or carboxylic acid groups did not suppress proteolysis but did mitigate hemolysis and biofilm production to an extent similar to DIF. Interestingly, chirality and the substitution of fluorine with chlorine resulted in a differential reduction in virulence phenotypes. Together, this pattern of data suggests virulence-suppressing pharmacophores of DIF and structural analogues integrate halogen, hydroxyl, and carboxylic acid moiety stereochemistry. The anti-virulence effects of DIF were achieved using concentrations that are safe in humans, do not impair platelet antimicrobial functions, do not affect S. aureus growth, and do not alter the efficacy of conventional antibiotics. These results offer proof of concept for using novel anti-virulence strategies as adjuvants to antibiotic therapy to address the challenge of MRSA infection.

Host-Bacterium Interaction Mechanisms in Staphylococcus aureus Endocarditis: A Systematic Review

Staphylococci sp. are the most commonly associated pathogens in infective endocarditis, especially within high-income nations. This along with the increasing burden of healthcare, aging populations, and the protracted infection courses, contribute to a significant challenge for healthcare systems. A systematic review was conducted using relevant search criteria from PubMed, Ovid's version of MEDLINE, and EMBASE, and data were tabulated from randomized controlled trials (RCT), observational cohort studies, meta-analysis, and basic research articles. The review was registered with the OSF register of systematic reviews and followed the PRISMA reporting guidelines. Thirty-five studies met the inclusion criteria and were included in the final systematic review. The role of Staphylococcus aureus and its interaction with the protective shield and host protection functions was identified and highlighted in several studies. The interaction between infective endocarditis pathogens, vascular endothelium, and blood constituents was also explored, giving rise to the potential use of antiplatelets as preventative and/or curative agents. Several factors allow Staphylococcus aureus infections to proliferate within the host with numerous promoting and perpetuating agents. The complex interaction with the hosts' innate immunity also potentiates its virulence. The goal of this study is to attain a better understanding on the molecular pathways involved in infective endocarditis supported by S. aureus and whether therapeutic avenues for the prevention and treatment of IE can be obtained. The use of antibiotic-treated allogeneic tissues have marked antibacterial action, thereby becoming the ideal substitute in native and prosthetic valvular infections. However, the development of effective vaccines against S. aureus still requires in-depth studies.

The Role of Platelets in Infective Endocarditis

Over the last decade, the incidence of infective endocarditis (IE) has increased, with a change in the frequency of causative bacteria. Early evidence has substantially demonstrated the crucial role of bacterial interaction with human platelets, with no clear mechanistic characterization in the pathogenesis of IE. The pathogenesis of endocarditis is so complex and atypical that it is still unclear how and why certain bacterial species will induce the formation of vegetation. In this review, we will analyze the key role of platelets in the physiopathology of endocarditis and in the formation of vegetation, depending on the bacterial species. We provide a comprehensive outline of the involvement of platelets in the host immune response, investigate the latest developments in platelet therapy, and discuss prospective research avenues for solving the mechanistic enigma of bacteria-platelet interaction for preventive and curative medicine.

Infective endocarditis and stroke: when does it bleed? A single center retrospective study

BACKGROUND

Infective endocarditis (IE) is a serious condition with a high mortality, represents a rare cause of stroke and an increased risk of intracranial hemorrhage. In this single center study, we characterize stroke patients with IE. We were interested in risk factors for intracranial hemorrhage and outcome of patients with intracranial hemorrhage compared to patients with ischemic stroke.

METHODS

Patients with IE and symptomatic ischemic stroke or intracranial hemorrhage admitted to our hospital between January 2019 and December 2022 were included in this retrospective study.

RESULTS

48 patients with IE and ischemic stroke or intracranial hemorrhage were identified. 37 patients were diagnosed with ischemic stroke, 11 patients were diagnosed with intracranial hemorrhage. The intracranial hemorrhage occurred within the first 12 days after admission. We identified Staphylococcus aureus detection and thrombocytopenia as risk factors for hemorrhagic complications. An increased in-hospital mortality in patients with intracranial hemorrhage (63.6% vs. 22%, p = 0.022) was found, whereas patients with ischemic stroke and patients with intracranial hemorrhage do not differ regarding favorable clinical outcome (27% vs. 27.3%, p = 1.0). 27.3% patients with intracranial hemorrhage and 43.2% patients with ischemic stroke underwent cardiac surgery. Overall, 15.7% new ischemic strokes occurred after valve reconstruction, whereas no new intracranial hemorrhage was observed.

CONCLUSIONS

We found an increased in-hospital mortality in patients with intracranial hemorrhage. Beside thrombocytopenia, we identified S. aureus detection as a risk factor for intracranial hemorrhage.

Low-Dose Aspirin for Venous Thromboembolism Prophylaxis is Associated With Lower Rates of Periprosthetic Joint Infection After Total Joint Arthroplasty

BACKGROUND

Aspirin as a venous thromboembolism (VTE) prophylactic agent has been shown to have antistaphylococcal and antibiofilm roles. Optimal acetylsalicylic acid (ASA) dosage would facilitate antimicrobial effects while avoiding over-aggressive inhibition of platelet antimicrobial function. Our purpose was to determine the periprosthetic joint infection (PJI) rate after total joint arthroplasty in patients receiving low-dose ASA (81 mg twice a day), in comparison to high-dose ASA (325 mg twice a day).

METHODS

We conducted a retrospective cohort study between 2008 and 2020. Eligible patients were older than 18 years, underwent primary total joint arthroplasty, both total knee arthroplasty and total hip arthroplasty, had a minimum 30-day follow-up, and received a full course ASA as VTE prophylaxis. Patients' records were reviewed for PJI, according to Musculoskeletal Infection Society criteria. Patients were excluded if they underwent revision arthroplasty, had a history of coagulopathy, or had an ASA regimen that was not completed. In total 15,825 patients were identified, 8,761 patients received low-dose ASA and 7,064 received high-dose ASA.

RESULTS

The high-dose cohort had a higher PJI rate (0.35 versus 0.10%, P = .001). This relationship was maintained when comparing subgroups comprising total knee arthroplasty (0.32 versus 0.06%, P = .019) or total hip arthroplasty (0.38 versus 0.14%, P = .035) and accounting for potentially confounding demographic and surgical variables (odds ratio = 2.59, 95% CI = 1.15-6.40, P = .028).

CONCLUSION

Comparing low-dose to high-dose ASA as a VTE prophylactic agent, low-dose ASA had a lower PJI rate. This may be attributable to a balance of anti-infective properties of ASA and antiplatelet effects.

Indonesian Mangrove Sonneratia caseolaris Leaves Ethanol Extract Is a Potential Super Antioxidant and Anti Methicillin-Resistant Staphylococcus aureus Drug

Methicillin-resistant Staphylococcus aureus (MRSA) is an S. aureus strain that has developed resistance against ß-lactam antibiotics, resulting in a scarcity of a potent cure for treating Staphylococcus infections. In this study, the anti-MRSA and antioxidant activity of the Indonesian mangrove species Sonneratia caseolaris, Avicennia marina, Rhizophora mucronata, and Rhizophora apiculata were studied. Disk diffusion, DPPH, a brine shrimp lethality test, and total phenolic and flavonoid assays were conducted. Results showed that among the tested mangroves, ethanol solvent-based S. caseolaris leaves extract had the highest antioxidant and anti-MRSA activities. An antioxidant activity assay showed comparable activity when compared to ascorbic acid, with an IC50 value of 4.2499 ± 3.0506 ppm and 5.2456 ± 0.5937 ppm, respectively, classifying the extract as a super-antioxidant. Moreover, S. caseolaris leaves extract showed the highest content of strongly associated antioxidative and antibacterial polyphenols, with 12.4% consisting of nontoxic flavonoids with the minimum inhibitory concentration of the ethanol-based S. caseolaris leaves extract being approximately 5000 ppm. LC-MS/MS results showed that phenolic compounds such as azelaic acid and aspirin were found, as well as flavonoid glucosides such as isovitexin and quercitrin. This strongly suggested that these compounds greatly contributed to antibacterial and antioxidant activity. Further research is needed to elucidate the interaction of the main compounds in S. caseolaris leaves extract in order to confirm their potential either as single or two or more compounds that synergistically function as a nontoxic antioxidant and antibacterial against MRSA.

Infective Endocarditis in High-Income Countries

Infective endocarditis remains an illness that carries a significant burden to healthcare resources. In recent times, there has been a shift from Streptococcus sp. to Staphylococcus sp. as the primary organism of interest. This has significant consequences, given the virulence of Staphylococcus and its propensity to form a biofilm, rendering non-surgical therapy ineffective. In addition, antibiotic resistance has affected treatment of this organism. The cohorts at most risk for Staphylococcal endocarditis are elderly patients with multiple comorbidities. The innovation of transcatheter technologies alongside other cardiac interventions such as implantable devices has contributed to the increased risk attributable to this cohort. We examined the pathophysiology of infective endocarditis carefully. Inter alia, the determinants of Staphylococcus aureus virulence, interaction with host immunity, as well as the discovery and emergence of a potential vaccine, were investigated. Furthermore, the potential role of prophylactic antibiotics during dental procedures was also evaluated. As rates of transcatheter device implantation increase, endocarditis is expected to increase, especially in this high-risk group. A high level of suspicion is needed alongside early initiation of therapy and referral to the heart team to improve outcomes.

Aspirin and Infection: A Narrative Review

Acetylsalicylic acid (ASA) is one of the most commonly used drugs in the world. It derives from the extract of white willow bark, whose therapeutic potential was known in Egypt since 1534 BC. ASA's pharmacological effects are historically considered secondary to its anti-inflammatory, platelet-inhibiting properties; however, human studies demonstrating a pro-inflammatory effect of ASA exist. It is likely that we are aware of only part of ASA's mechanisms of action; moreover, the clinical effect is largely dependent on dosages. During the past few decades, evidence of the anti-infective properties of ASA has emerged. We performed a review of such research in order to provide a comprehensive overview of ASA and viral, bacterial, fungal and parasitic infections, as well as ASA's antibiofilm properties.

Association Between Aspirin Use and Decreased Risk of Pneumonia in Patients With Cardio-Cerebra-Vascular Ischemic Disease: A Population-Based Cohort Study

This study evaluated the association between long-term low-dose aspirin use and decreased risk of pneumonia in patients with cardio-cerebra-vascular ischemic diseases (CCVDs). This retrospective cohort study used records from Taiwan's National Health Insurance Research Database of claims made between 1997 and 2013. After propensity score matching (PSM), patients who took a low dose of aspirin for more than 90 days within 1 year of diagnosis with CCVDs were identified as the exposure group (n = 15,784). A matched total of 15,784 individuals without aspirin use were selected for the non-aspirin group. The main outcome was the development of pneumonia after the index date. Multivariable Cox regression analysis and Kaplan-Meier survival analysis were performed to estimate the adjusted hazard ratio (aHR) and cumulative probability of pneumonia. The result after PSM indicated a lower hazard ratio for pneumonia in aspirin users (aHR = 0.890, 95% confidence interval = 0.837-0.945). Therefore, patients with CCVDs who took aspirin had a lower risk of developing pneumonia than those who did not. In conclusion, this population-based cohort study demonstrated that long-term low-dose aspirin use is associated with a slightly decreased risk of pneumonia in patients with CCVDs.

Salicylic acid stabilizes Staphylococcus aureus biofilm by impairing the agr quorum-sensing system

Salicylic acid (SAL) has recently been shown to induce biofilm formation in Staphylococcus aureus and to affect the expression of virulence factors. This study was aimed to investigate the effect of SAL on the regulatory agr system and its impact on S. aureus biofilm formation. The agr quorum-sensing system, which is a central regulator in S. aureus pathogenicity, plays a pivotal role in the dispersal of S. aureus mature biofilms and contributes to the creation of new colonization sites. Here, we demonstrate that SAL impairs biofilm dispersal by interfering with agr expression. As revealed by our work, protease and surfactant molecule production is diminished, and bacterial cell autolysis is also negatively affected by SAL. Furthermore, as a consequence of SAL treatment, the S. aureus biofilm matrix revealed the lack of extracellular DNA. In silico docking and simulation of molecular dynamics provided evidence for a potential interaction of AgrA and SAL, resulting in reduced activity of the agr system. In conclusion, SAL stabilized the mature S. aureus biofilms, which may prevent bacterial cell dissemination. However, it may foster the establishment of infections locally and consequently increase bacterial persistence leading to therapeutic failure.

Statins potentiate the antibacterial effect of platelets on Staphylococcus aureus

Platelets have largely demonstrated their implication in anti-infectious immunity. This effect is ensured by the secreted molecules stored mostly in platelet alpha granules. Previous studies have reported that Staphylococcus aureus showed sensitivity to this antibacterial effect of platelets. Statins, for their part, have shown a modulating effect on platelet activation. Furthermore, several studies have reported a protective effect of statins in staphylococcal endocarditis. The aim of this study was to investigate the influence of statins on the antibacterial effect of washed platelets. Blood samples were collected from healthy donors (n = 35). PRP was prepared according to the ISTH recommendation. Bacteria were incubated for four hours with untreated-washed platelets, or rather treated by statins and/or GPIIbIIIa antagonists. In order to evaluate the antibacterial effect, the platelet-bacteria mix was spread on the blood agar to count the number of colonies after 18 hours of incubation. Measurement of CD 41 and CD62P expression by flow cytometry was performed to evaluate the effect of statin on bacterial-induced platelet activation. Statins have shown a potentiation of the antibacterial effect of washed platelets (p < .01 for Atorvastatin and Rosuvastatin and p < .001 for Fluvastatin vs untreated washed platelets condition). This effect of statins was dose-dependent and was more significant at 20 μM. The addition of Fluvastatin to platelet-bacterial mix significantly increased the expression of platelet CD41 and CD62P (p < .05 and p < .01 vs resting washed platelets, respectively). Tirofiban, GPIIbIIIa antagonist, reversed the antibacterial effect of washed platelets and suppressed the potentiating effect of statins. Our study demonstrated that statins potentiate the anti-staphylococcal effect of washed platelets. This result may explain the beneficial effect of statins on Staphylococcus aureus infective endocarditis. Further studies are therefore required to explain this effect at the molecular level and to assess its impact in vivo.

Antiplatelet Agents Have a Distinct Efficacy on Platelet Aggregation Induced by Infectious Bacteria

Platelets are the cornerstone of hemostasis. However, their exaggerated aggregation induces deleterious consequences. In several diseases, such as infectious endocarditis and sepsis, the interaction between platelets and bacteria leads to platelet aggregation. Despite platelet involvement, no antiplatelet therapy is currently recommended in these infectious diseases. We aimed here, to evaluate, in vitro, the effect of antiplatelet drugs on platelet aggregation induced by two of the bacterial pathogens most involved in infectious endocarditis, Staphylococcus aureus and Streptococcus sanguinis. Blood samples were collected from healthy donors (n = 43). Treated platelet rich plasmas were incubated with three bacterial strains of each species tested. Platelet aggregation was evaluated by Light Transmission Aggregometry. CD62P surface exposure was evaluated by flow cytometry. Aggregate organizations were analyzed by scanning electron microscopy. All the strains tested induced a strong platelet aggregation. Antiplatelet drugs showed distinct effects depending on the bacterial species involved with different magnitude between strains of the same species. Ticagrelor exhibited the highest inhibitory effect on platelet activation (p <0.001) and aggregation (p <0.01) induced by S. aureus. In the case of S. sanguinis, platelet activation and aggregation were better inhibited using the combination of both aspirin and ticagrelor (p <0.05 and p <0.001 respectively). Aggregates ultrastructure and effect of antiplatelet drugs observed by scanning electron microscopy depended on the species involved. Our results highlighted that the effect of antiplatelet drugs depended on the bacterial species involved. We might recommend therefore to consider the germ involved before introduction of an optimal antiplatelet therapy.

The distinct effects of aspirin on platelet aggregation induced by infectious bacteria

Bacteria induce platelet aggregation triggered by several mechanisms. The goal of this work was to characterize platelet aggregates induced by different bacterial strains and to quantify the effect of aspirin treatment using aggregation tests, as well as a novel approach based on confocal analysis. Blood samples were obtained from either healthy donors (n = 27) or patients treated with long-term aspirin (n = 15). The bacterial species included were Staphylococcus aureus, Enterococcus faecalis, and Streptococcus sanguinis. The different aggregate's ultrastructures depending on the bacterial strain were analyzed using Scanning electron microscopy. Quantification of the size of the platelet aggregates, their mean number as well as the bacterial impregnation within the aggregates was performed using confocal laser scanning light microscopy. Light Transmission Aggregometry was also performed. Our results reported distinct characteristics of platelet aggregates depending on the bacterial strain. Using confocal analysis, we have shown that aspirin significantly reduced platelet aggregation induced by S. aureus (p = .003) and E. faecalis (p = .006) with no effect in the case of S. sanguinis (p = .529). The results of the aggregometry were concordant with those of the confocal technique in the case of S. aureus and S. sanguinis. Interestingly, aggregation induced by E. faecalis was detected only with confocal analysis. In conclusion, our confocal scanning microscopy allowed a detailed study of the platelet aggregation induced by bacteria. We showed that aspirin acts on bacterial-induced platelet aggregation depending on the species. These results are in favor of the use of aspirin considering the species and the bacterial strain involved.