Infections constitute a multiple and heterogeneous set of pathologies, and the first cause of mortality worldwide. Among them, sepsis is a more recent nosological entity, including the most severe forms of acute infectious pathologies, its frequency increasing considerably over time. It is considered to be the cause of more than 27 million deaths per year, more than 4,000 deaths per day in the United States and about 200 deaths per day in intensive care units in France.

The occurrence of hemodynamic failure within visceral damage is a poor prognostic factor, the lethality in this situation can reach 60% of affected patients. The amount of organ dysfunction is also prognostic. More worryingly, the initial mortality is aggravated by the persistence of the negative evolution after hospital treatment, the 5-year prognosis being significantly more severe in the population of patients treated for sepsis than in the general population, particularly in the case of respiratory or cardiovascular damage during the stay in intensive care. The most frequent causes of these severe infections in the ICU are lower respiratory infections, particularly pneumonia acquired under mechanical ventilation, urinary tract infections and digestive tract infections.

Sepsis corresponds to an infection of particular severity, which results in the association of organ failures, the type and severity of which vary according to the patient, the origin of the infection and the pathogen responsible. The severity of the picture will require specific management and may necessitate the introduction of organ supplements or even lead to death in the most serious forms.

Infections by enterobacteria and in particular Klebsiella spp. are frequent in the intensive care unit. The association with antibiotic resistance and especially with ESBL production is a daily clinical situation. During these infections, the prognosis is variable, sometimes very poor, without it being possible to determine whether this evolution is due to antibiotic resistance or to the virulence of the pathogen. The objective of this work is to study the structure of lipid A of ESBL-producing Klebsiella strains responsible for nosocomial infections. This study is part of the "EVENT" protocols of which it is an ancillary analysis.

The objective of this study is to evaluate the role of the presence of 2-hydroxymyristate within lipid A of the lipopolysaccharide in the prognosis of ESBL-producing Klebsiella infections in the ICU. The secondary objectives correspond to the evaluation of the vital prognosis according to the infected organ (lung, kidney, digestive system), and the presence of 2-hydroxymyristate and the risk of bacteremia.

Inclusion Criteria:

• Patient whose age is ≥ 18 years
• Patient hospitalized in an intensive care unit
• Patient with a nosocomial infection with ESBL-producing Klebsiella
• French-speaking patient

Exclusion Criteria:

• Patient with a severe psychiatric disorder
• Patient under guardianship or curatorship
• Patient deprived of liberty
• Patient under court protection
• Patient who objects to the use of his or her data for this research

These patients were hospitalized in the ICU with nosocomial ESBL-producing Klebsiella infection between 2011 and 2016.