Flow Cytometry Analysis of the Reactive Oxygen Species in Immature Granulocytes in Septic Patient

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection. The immune system is activated by both pathogen-associated and host-derived molecular patterns. A strong response of neutrophils is engaged and both innate and adaptive immune system homeostasis are strongly affected. Neutrophils are able to produce high concentrations of inducible reactive oxygen species (ROS), leading to an oxidative stress. ROS can be released extracellularly at the site of infection or intracellularly in the phagolysosome. At early phase of sepsis, immature granulocytes are present in the bloodstream and could help to predict sepsis deterioration. However, it has also been shown that they are less efficient than mature granulocytes in ROS production and phagocytosis. ROS are potent stressors for bacteria and can directly or indirectly damage DNA. Bacteria can protect against DNA damage through the SOS response, which is a coordinated cellular response regulated by a repressor, LexA, and a sensor/activator, RecA. The bacterial SOS response is involved in acquisition of resistances to antibiotics through increasing frequencies of spontaneous mutations or increasing the expression of resistance and adaptation genes. The hypothesis that the low-level production of ROS by immature granulocytes in the early steps of sepsis could be beneficial for both the host, as a high level of ROS induce organ damage and dysfunction, and the pathogen, as low concentrations of ROS would be able to induce the SOS response allowing bacteria to enhance an adaptive response. The main objective it is to evaluate the level of ROS produced by the immature granulocytes in septic patient. Then, it will be assess if it could promote antibiotic resistance expression via SOS-induced integron gene cassette rearrangements.