Microscopic Description of Platelet Aggregates Induced by Escherichia coli Strains

Abstract

In addition to their role in haemostasis, platelets are also involved in the inflammatory and antimicrobial process. Interactions between pathogens and platelets, mediated by receptors can lead to platelet activation, which may be responsible for a granular secretion process or even aggregation, depending on the bacterial species. Granular secretion releases peptides with bactericidal activity as well as aggregating factors. To our knowledge, these interactions have been poorly studied for Escherichia coli (E. coli). Few studies have characterised the cellular organization of platelet-E. coli aggregates. The objective of our study was to investigate the structure of platelet aggregates induced by different E. coli strains as well as the ultrastructure of platelet-E. coli mixtures using a scanning and transmission electron microscopy (SEM and TEM) approach. Our results show that the appearance of platelet aggregates is mainly dependent on the strain used. SEM images illustrate the platelet activation and aggregation and their colocalisation with bacteria. Some E. coli strains induce platelet activation and aggregation, and the bacteria are trapped in the platelet magma. However, some strains do not induce significant platelet activation and are found in close proximity to the platelets. The structure of the E. coli strains might explain the results obtained.

The Role of Platelets in Infective Endocarditis

“…Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are two advanced techniques used in the study of platelets and their interactions with pathogens, such as bacteria [114]. TEM offers a detailed view of platelet granules, platelet defects, and organelle dynamics at high magnification [115], while SEM provides a high-resolution surface view of platelets and their behavior when they are in contact with different pathogens [116]. Moreover, we developed a new approach for the analysis of the heart valve ultrastructure of IE patients by combining SEM and energy-dispersive X-ray spectroscopy which allowed us to characterize the chemical profile of the cardiac valves infected with Viridans streptococci as well as the arrangement of the different cells on the infected valve [58].…”