Prospective Study of Staphylococcus Aureus Clinical Isolates Versus Colonization: RNAs as Potential Biomarkers for Bloodstream Infections

Staphylococcus aureus ranks among the top three organisms for community-acquired, healthcare-related and nosocomial infections in humans. It lives as a commensal organism but can also provoke very severe diseases. Identifying markers of the 'colonization/disease' transition is of paramount importance. We recently found that an association of two regulatory RNAs was associated with S. aureus infection rather than colonization and with the severity of infection. Those preliminary results have to be confirmed with a more important prospective cohort.

Inclusion criteria

• Patient over 18 years of age;
• Patients hospitalized at the University Hospital of Rennes, with according to groups:

• : Colonized subjects:

• Any patient hospitalized at the University Hospital of Rennes, or any health professional, in whom a colonization screening with S. aureus is performed in routine care and a colonization with S. aureus is documented;

(For information, this screening is carried out frequently at the University Hospital of Rennes for different reasons (before surgery or procedure requiring the installation of equipment, screening of contact cases of infected cases, investigation during a nosocomial epidemic...). These people are hospitalized for reasons other than S. aureus infection and in different departments, but the samples are collected centrally in the institution's bacteriology laboratory.)

• : Patients hospitalized for BSA:

• Patients hospitalized in the infectious diseases and medical intensive care unit and in the surgical intensive care unit, for whom a BSA is documented at the bacteriology laboratory of the University Hospital of Rennes;
• Patients for whom nasal carrying screening for S. aureus is prescribed as part of their management;
• These patients will be classified into two groups:

• Serious clinic (CG):
• BSA ;
• Associated with signs of sepsis according to the 20168 international definition:

• SOFA score (see Appendix 3) 2 ;
• Septic shock will be defined as the existence of sepsis associated with persistent low blood pressure requiring the administration of vasopressors to obtain an average blood pressure (MAP) 65 mmHg and an arterial lactate dosage 2 mmol/L despite adequate vascular filling.

• Non-serious clinic (CNG):
• BSA ;
• Which does not meet the definition of the CG group.
• Having expressed their opposition to this research or whose trusted person does not oppose the research if the patient is not able to give an informed opinion.

Exclusion criteria

• Pregnant or breastfeeding women;
• Persons of full age who are subject to legal protection (protection of justice, guardianship, guardianship), persons deprived of their liberty;
• S. aureus strain producing leucocidin from Panton-Valentine;