Changes in ROS/RNS Levels in Endothelial Cells in Experimental Bacteremia.

A high-precision system was developed for the quantification of biological analytes in single cells (reactive oxygen species (ROS) and reactive nitrogen species (RNS)) based on the electrochemical amperometric method. The efficacy of this system was evaluated using an experimental bacteremia model. Endothelial cells exhibited increased ROS/RNS production when stimulated by Staphylococcus aureus. However, they remained inactive when exposed to either unprimed or primed neutrophils that had been pre-incubated with bacteria. It is noteworthy that the sequential stimulation of endothelial cells with bacteria followed by neutrophils resulted in a significant increase in the ROS/RNS level, which demonstrated a correlation with the number of neutrophils in contact with the endothelial cells. These results highlight the potential of our system to quantitatively assess ROS/RNS dynamics in complex biological systems. They also offer insights into the interplay between various cellular components in experimental bacteremia.

Differences in bacteria nanomotion profiles and neutrophil nanomotion during phagocytosis.

The main goal of this work is to highlight the connection between nanomotion and the metabolic activity of living cells. We therefore monitored the nanomotion of four different clinical strains of bacteria (prokaryotes) and the bacterial phagocytosis by neutrophil granulocytes (eukaryotes). All clinical strains of bacteria, regardless of their biochemical profile, showed pronounced fluctuations. Importantly, the nature of their nanomotions was different for the different strains. Flagellated bacteria (Escherichia coli, Proteus mirabilis) showed more pronounced movements than the non-flagellated forms (Staphylococcus aureus, Klebsiella pneumoniae). The unprimed neutrophil did not cause any difference in cantilever oscillations with control. However, in the process of phagocytosis of S. aureus (metabolically active state), a significant activation of neutrophil granulocytes was observed and cell nanomotions were maintained at a high level for up to 30 min of observation. These preliminary results indicate that nanomotion seems to be specific to different bacterial species and could be used to monitor, in a label free manner, basic cellular processes.