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Updated: Jun 25, 2025
Flow Cytometric Measurement Of ROS Production In Macrophages In Response To FcγR Cross-linking
Published on: March 7, 2019
Phagosomal granulocytic ROS in septic patients induce the bacterial SOS response
Stecy Chollet1, Ana Catalina Hernandez Padilla1, Thomas Daix1,2,3
1University Limoges, Inserm, CHU Limoges, RESINFIT, U 1092, F-87000 Limoges, France.
Abstract:
Septic patients with worst clinical prognosis have increased circulating immature granulocytes (IG), displaying limited phagocytosis and reactive oxygen species (ROS) production. Here, we developed an ex vivo model of incubation of human granulocytes, from septic patients or healthy donors, with Escherichia coli. We showed that the ROS production in Sepsis-IG is lower due to decreased activation and protein expression of the NADPH oxidase complex. We also demonstrated that the low level of ROS production and lower phagocytosis of IG in sepsis induce the bacterial SOS response, leading to the expression of the SOS-regulated quinolone resistance gene qnrB2. Without antimicrobial pressure, the sepsis immune response alone may promote antibiotic resistance expression.
Insights
Immature granulocytes (IG) in sepsis patients show reduced function, impairing bacterial clearance. This immune deficiency can unexpectedly drive antibiotic resistance gene expression in bacteria.
Area of Science:
- Immunology
- Microbiology
- Molecular Biology
Background:
- Septic patients with poor prognosis exhibit increased circulating immature granulocytes (IG).
- These IG cells demonstrate diminished phagocytic capacity and reduced reactive oxygen species (ROS) production.
- The clinical implications of these functional deficits in sepsis remain incompletely understood.
Purpose of the Study:
- To investigate the functional capabilities of IG from septic patients.
- To determine the impact of sepsis-derived IG on bacterial responses, specifically antibiotic resistance.
- To elucidate the mechanisms underlying altered IG function in sepsis.
Main Methods:
- Development of an ex vivo model using human granulocytes from septic patients and healthy donors.
- Incubation of granulocytes with Escherichia coli.
- Assessment of reactive oxygen species (ROS) production and phagocytosis.
- Analysis of NADPH oxidase complex activation and protein expression.
- Evaluation of bacterial SOS response and quinolone resistance gene (qnrB2) expression.
Main Results:
- Granulocytes from septic patients (Sepsis-IG) exhibited significantly lower ROS production compared to healthy controls.
- Decreased activation and protein expression of the NADPH oxidase complex were observed in Sepsis-IG.
- Lower ROS production and phagocytosis by Sepsis-IG induced the bacterial SOS response.
- This bacterial response led to the upregulation of the qnrB2 gene, conferring quinolone resistance.
Conclusions:
- The impaired function of immature granulocytes in sepsis contributes to reduced bacterial clearance.
- Sepsis-induced immune dysfunction can inadvertently promote the emergence of antibiotic resistance.
- These findings highlight a novel mechanism linking sepsis pathophysiology to the development of antimicrobial resistance, independent of direct antibiotic pressure.
