The Role of Platelets in Infective Endocarditis

Understanding Bartonella-Associated Infective Endocarditis: Examining Heart Valve and Vegetation Appearance and the Role of Neutrophilic Leukocytes

BACKGROUND

The endocardium and cardiac valves undergo severe impact during infective endocarditis (IE), and the formation of vegetation places IE patients at a heightened risk of embolic complications and mortality. The relevant literature indicates that 50% of IE cases exhibit structurally normal cardiac valves, with no preceding history of heart valve disease. Gram-positive cocci emerge as the predominant causative microorganisms in IE, while Gram-negative Bartonella spp., persisting in the endothelium, follow pathogenic pathways distinct from those of typical IE-causing agents. Employing clinical as well as advanced microbiological and molecular assays facilitated the identification of causative pathogens, and various morphological methods were applied to evaluate heart valve damage, shedding light on the role of neutrophilic leukocytes in host defense. In this research, the immunohistochemical analysis of neutrophilic leukocyte activation markers such as myeloperoxidase, neutrophil elastase, calprotectin, and histone H3, was performed. A distinct difference in the expression patterns of these markers was observed when comparing Bartonella spp.-caused and non-Bartonella spp.-caused IE. The markers exhibited significantly higher expression in non-Bartonella spp.-caused IE compared to Bartonella spp.-caused IE, and they were more prevalent in vegetation than in the valvular leaflets. Notably, the expression of these markers in all IE cases significantly differed from that in control samples. Furthermore, we advocated the use of 16S rRNA Next-Generation Sequencing on excised heart valves as an effective diagnostic tool for IE, particularly in cases where blood cultures yielded negative results. The compelling results achieved in this study regarding the enigmatic nature of Bartonella spp. IE's pathophysiology contribute significantly to our understanding of the peculiarities of inflammation and immune responses.

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.