The CYTOBACT project was selected in the framework of the Carnot call for projects organized for the University Hospital Federations (UHF)

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CYTOBACT: Combining cell surface biomarkers of circulating leukocytes in flow cytometry to differentiate bacterial and viral infections in the emergency department.

The identification of the bacterial or viral etiology of an infection is rarely available in real time to the clinician, especially in the emergency room. This lack of etiological identification is one of the major determinants of the overconsumption of antibiotics (ATB), which in turn contributes to the emergence of bacteria highly resistant to ATB.
The CYTOBACT study aims at confirming, in a multicenter validation cohort, the excellent performance of combinations of cell surface markers of circulating blood cells (measured by flow cytometry) to differentiate bacterial from viral infections in patients consulting the emergency department for an infectious syndrome. In the BIPS pilot study we conducted, the combination of HLA-DR (human leukocyte antigen) on monocytes and MerTk (Myeloid-epithelial-reproductive tyrosine kinase) on neutrophils appeared to be particularly effective (area under the ROC curve (AUC) of 0.91 [95% confidence interval 0.88;0.94]) for the diagnosis of bacterial infection. Among patients thus defined as having no bacterial infection, another combination of cellular markers (CD64 and CD24 on neutrophils and CX3CR1 on monocytes) is associated with an AUC of 0.98 [0.96;1] for identifying a viral infection. Given the monocentric nature and the limited number of patients studied, it is essential to set up a multicentric validation cohort to confirm, on the one hand, the performance of flow cytometry and, on the other hand, the best combinations of cell surface biomarkers in this indication, before envisaging a transfer of technology into routine use.
In this competitive field, where solutions using proteomics or transcriptomics are also being developed internationally, the transfer prospects are the development of a delocalized cytometer solution to measure these markers as close as possible to clinical decision-making, and thus better characterize infectious episodes and rationalize antibiotic prescriptions by limiting them to bacterial infections.

The CYTOBACT cohort has been selected for funding under the Institut Carnot call for proposals.
Pierre Hausfater , Professor of Emergency Medicine, Head of the Emergency Department at the Pitié-Salpêtrière Hospital, AP-HP Sorbonne University Group.