The Antibacterial Effect of Platelets on Escherichia coli Strains

Abstract

Platelets play an important role in defense against pathogens; however, the interaction between Escherichia coli and platelets has not been well described and detailed. Our goal was to study the interaction between platelets and selected strains of E. coli in order to evaluate the antibacterial effect of platelets and to assess bacterial effects on platelet activation. Washed platelets and supernatants of pre-activated platelets were incubated with five clinical colistin-resistant and five laboratory colistin-sensitive strains of E. coli in order to study bacterial growth. Platelet activation was measured with flow cytometry by evaluating CD62P expression. To identify the difference in strain behavior toward platelets, a pangenome analysis using Roary and O-antigen serotyping was carried out. Both whole platelets and the supernatant of activated platelets inhibited growth of three laboratory colistin-sensitive strains. In contrast, platelets promoted growth of the other strains. There was a negative correlation between platelet activation and bacterial growth. The Roary results showed no logical clustering to explain the mechanism of platelet resistance. The diversity of the responses might be due to strains of different types of O-antigen. Our results show a bidirectional interaction between platelets and E. coli whose expression is dependent on the bacterial strain involved.

Microscopic Description of Platelet Aggregates Induced by Escherichia coli Strains

“…Structural analysis by electron microscopy of the strains could explain our results. This structural variability of the platelet- E. coli mixture confirmed our previous results and complements them [ 9 ].…”

“…The strains used in this study were selected from each group based on our previous results [ 9 ]. The two main selection criteria are the capacity of the strain to induce platelet activation and the profile toward the platelet inhibitory effect ( Table 1 ).…”

“…As previously described [ 6 ], 200 µL of living PBS-washed platelets (4 × 10 8 /mL) and of PBS-washed bacteria (10 9 CFU/mL) were mixed for one hour at 37 °C [ 9 ], under rotation to avoid the static state and the development of aggregates due to gravity. Cells were then fixed using 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer for one hour.…”

“…Recently, we studied the antibacterial effect of platelets on different strains of E. coli . It was found that this bactericidal activity was strain dependent [ 9 ]. We also observed a correlation between this bactericidal effect and the capacity of strains to induce platelet activation [ 9 ].…”

“…It was found that this bactericidal activity was strain dependent [ 9 ]. We also observed a correlation between this bactericidal effect and the capacity of strains to induce platelet activation [ 9 ]. Indeed, some E. coli strains induced platelet activation, a result that brought into question the platelet aggregation capability of these strains [ 8 , 9 ].…”