Identification of Clinical, Genetic and Immunological Factors Involved in the Development of Severe Bacterial Infections in Pediatrics

Severe bacterial infections (SBI) are responsible for significant morbidity and mortality in the paediatric population. There is considerable individual variability in children's susceptibility to developing SBIs. This variability is multifactorial, and the mechanisms at work are not yet fully understood. The investigators of this study therefore propose to study a population of children who had particularly severe bacterial infections requiring hospitalization in a pediatric intensive care unit in France between 2015 and 2018. This study is part of a global approach to understanding the mechanisms favoring the occurrence of IBS in pediatrics. The study will initially focus on analyzing the clinical phenotype of these children in terms of the type of infection presented, as well as immunologically with an immune workup of all these patients. The investigators also plan to contact each family individually to identify other episodes of personal or family IBS or other elements suggestive of immune deficiency (opportunistic infections, autoimmune manifestations, severe atopy). The investigators will also assess the persistent sequelae since their infectious episode, and their quality of life following this IBS. In parallel, the genetic analysis of these patients and their parents will be carried out using whole-exome sequencing. The investigators will compare the results with those obtained in 2 IBS-free control populations (N=70 and N=116). The goal is to identify genetic variants that favor the occurrence of IBS in general, and some that are specific to certain bacteria or clinical presentations.

Inclusion Criteria: For patients: * Patient included in the DIABACT IV study between 2015 and 2018, following hospitalization in a pediatric intensive care unit in France for a severe bacterial infection. * Patient affiliated to a social security system * Patient alive at the time of inclusion. * Written consent from legal representatives for participation in research. If one of the legal representatives is unable to complete/sign the written consent, it will be sought orally by telephone and recorded in the patient's file. If the patient is over 18, written consent will be obtained. If the patient is a minor, consent will be sought with communication adapted to his/her level of understanding and age. For parents: * Patient's biological parents * Written consent Exclusion Criteria: * Persons under court protection * Refusal to participate in research