Pathogenic Escherichia coli change the adhesion between neutrophils and endotheliocytes in the experimental bacteremia model.

Septicemia caused by gram-negative bacteria is characterized by high death rate due to the endotoxin release. Since the septicemia depends not only on biochemical aspects of interactions in the system bloodstream, the study of mechanical interactions is also important. Using a model of experimental septicemia caused by E. coli, a hyperproduction of integrins CD11a and CD11b by neutrophils was shown, but this did not lead to the establishment of strong adhesion contacts between endothelial cells and neutrophils. On the contrary, adhesion force and work, as assessed by FS spectroscopy, were statistically significantly reduced in the presence of bacteria. It has also been shown that exposure to the pathogenic strain E. coli 321 increases the stiffness of the membrane-cytoskeleton complex of endothelial cells and bacteria significantly change their morphology on long-term observation. At the same time, we observed the death of neutrophils by apoptosis. Thus, it was shown that besides lipopolysaccharide release there are other pathogenic factors of E. coli: decrease in the interaction between neutrophil and endothelial cell caused by an increase of the endothelial cell rigidity and apoptotic death of neutrophils probably as a result of adhesins and exotoxin effects. Obtained results should be taken in mind during the therapy of septicemia.