Breast milk contains many microorganisms including bacteria that are beneficial to health (probiotics), but also bacteria that are generally considered pathogenic.

Several studies have described an increased risk of infections due to pathogenic germs in breast milk in premature newborns whose digestive system is immature and whose digestive flora is modified by repeated antibiotic treatments.

However, a breastfed baby is better protected against infectious diseases than a bottle-fed baby. The objective of this study is to define the breast milk microbiota of infants with confirmed early or late neonatal bacterial infection compared to the breast milk microbiota of infants with no evidence of bacterial infection. For that purpose, an exploration will be performed using the principle of "Microbial Culturomics" and targeted metagenomics (16S ribosomal RNA gene sequencing).

Inclusion Criteria:

Breastfeeding mothers of infants:

• Aged 1 to 89 days consulting in hospitals in the Marseille area (Assistance Publique des Hôpitaux de Marseille: Hôpital de la Timone-enfants and Hôpital Nord),
• Suspected neonatal bacterial infection due to the presence of fever (rectal or axillary temperature > 38°C),
• In whom bacteriological samples have been taken (cerebrospinal fluid, joint fluid, blood cultures, urine),
• Patients affiliated or benefiting from a social security system.

Exclusion Criteria:

• Exclusive formula milk feeding
• Opposition of legal guardians
• No bacteriological sample to prove infant infection
• No confirmation of fever by standardized method
• Opposition to participating in the study
• Neonatal hospitalization > 48 hours for management of prematurity.
• Severe congenital malformations in the infant.
• Antibiotic treatment for a concomitant bacterial infection in the infant.

Breastfeeding mothers