This study will help determine whether the SeptiCyte LAB test can accurately differentiate between SIRS and actual infections in postoperative patients, potentially reducing unnecessary antibiotic use and improving patient outcomes in cases of acute mesenteric ischemia

Introduction Early diagnosis of bacterial infections is crucial in intensive care, as conditions such as sepsis and septic shock are emergencies with high mortality rates. Conversely, Systemic Inflammatory Response Syndrome (SIRS) is a deregulated response to an insult without an infectious origin. SIRS is common post-major surgery and complicates the diagnosis between a simple inflammatory response and an actual infection. Although antibiotic therapy is undisputed in septic shock, the rise of antibiotic resistance and the lack of new antibiotics demand a judicious and well-argued prescription in probable sepsis cases. Rapid diagnostics are essential to identify patients who will benefit from empirical antibiotic therapy.

Current Diagnostic Challenges Microbiological documentation remains the gold standard for confirming sepsis or septic shock. However, the delay in obtaining standard bacteriology results poses a risk to patient survival. Biomarkers like CRP and PCT have been proposed for sepsis diagnosis, but their reliability is limited by numerous confounding factors, making them less specific.

The SeptiCyte LAB Test Recent advances in sequencing technology have made molecular biology techniques more accessible and rapid. SeptiCyte LAB is a molecular test based on the quantitative sequencing of mRNA from four genes (CEACAM4, LAMP1, PLA2G7, and PLAC8) involved in bacterial infection signaling. Studies have shown a specificity of 94% and a negative predictive value of 98.8% in ICU patients suspected of sepsis, with a threshold value above 4. These results have also been confirmed in elective esophageal surgery populations, demonstrating encouraging statistical performance.

Relevance to Acute Mesenteric Ischemia (AMI) AMI is a rare and difficult-to-diagnose condition with high diagnostic delays and mortality rates. Its initial presentation often mimics sepsis or septic shock, leading to the early administration of broad-spectrum empirical antibiotics due to fears of bacterial translocation or perforation. Although surgical guidelines encourage systemic antibiotic use, there is insufficient evidence for its routine application.

Study Objective While data on the SeptiCyte LAB test is available for cardiac and digestive surgeries, there is none for vascular surgery. This study aims to evaluate the SeptiCyte LAB test's ability to identify postoperative SIRS patients to reduce empirical antibiotic use while awaiting standard bacteriology results and to assess the impact of surgery on the SeptiCyte LAB test. We will study patients admitted to intensive care units pre- and post-open laparotomy for the treatment of embolic or thrombotic AMI.

Inclusion Criteria:

• Patient aged over 18 years
• Affiliated to health assurance system
• Hospitalized in the ICU for confirmed mesenteric ischemia* for less than 24 hours with an indication for laparotomy
• Hospitalized in the ICU for confirmed mesenteric ischemia* who underwent laparotomy for revascularization or digestive resection less than 24 hours ago
• Intraoperative bacteriological samples and blood cultures performed within 24 hours of medical management

Exclusion Criteria:

• decline to participate
• no consent available

Adult patient with suspected of confirmed acute mesenteric ischemia who required urgent surgery for revascularisation and/or intra-abdominal infection