Late-onset neonatal sepsis (LOS), occurring in newborn of at least 7 days of life, is frequently observed in Neonatal Intensive Care Units (NICUs) and potentially severe (mortality, neurologic and respiratory impairments).

Despite its high prevalence, a reliable diagnostic remains difficult. Currently, nonspecific clinical signs that might be related to other neonatal conditions such as prematurity and birth defects, are used to determine the diagnosis of LOS. Laboratory results of biological markers, such as C-Reactive Protein (CRP) and Procalcitonin (PCT) are often delayed in comparison with LOS onset. Blood culture results are too late and lack sensitivity. This explains why excessive antibiotic use is observed in a large proportion of NICU hospitalized newborns. This results in an increased antibiotic resistance, microbiota modification, neonatal complications (pulmonary, ophthalmologic and neurologic) and mortality.

A previous study (EMERAUDE) aimed to identify new biomarkers to early exclude the diagnosis of LOS, in order to limit antibiotic overuse. This study including 230 neonates revealed high performances of IL6, IL10, NGAL and combinations of PCT/IL10 and PTX3/NGAL.

The main objective of the present study will be to validate the performances of these biomarkers in another cohort. The secondary objectives will be to explore transcriptomic biomarkers and salivary biomarkers.

Inclusion Criteria:

• Patient hospitalized in the NICU of one of the two recruiting centers at the time of inclusion
• Patients aged ≥ 7 days
• Patients weighted ≥ 500 g the day of blood sample
• patients with suggestive signs of LOS including at least one of the following:Fever > 38°C; tachycardia > 160bpm; capillary refill time > 3 seconds; grey and/or pale skin complexion; apnea/ bradycardia syndrome, bloating; vomiting; rectal bleeding; hypotonia; lethargy; seizures without other obvious cause; increased ventilatory support and/or increased FiO2; cutaneous rash; inflammation at the needle-puncture site of the central venous catheter; or any other condition for which the clinician suspected an infection
• patients with a standard of care blood sampling, including at least a blood culture;

Exclusion Criteria:

• Patient treated with antibiotics for a bacteriologically confirmed infection at the time of sampling or within 48 hours prior to sampling
• Patient who underwent surgery within the previous 7 days
• Patients vaccinated within the previous 7 days
• Patient who received treatment with systemic corticosteroid therapy in the 48 hours prior to sampling
• Patient with severe combined immunodeficiency
• Opposition from parent(s)/guardian(s)

Newborns aged ≥ 7 days hospitalized in one of the 2 neonatal intensive care units (Nantes or Lyon) for whom an infection is suspected.