The intestinal flora is a complex ecosystem which is known to play various important functions in the gut. Recent data have reported a delay in intestinal colonization in preterm. Modulating the intestinal flora through dietary supplementation with probiotics or prebiotics has been shown to improve digestive and general outcomes in full-term infants.The aim of this study was to evaluate the clinical tolerance, the effect on gut microbiota, and the mucosal inflammatory responses to a fermented milk in preterm infants.

This prospective, randomized, double-blind, controlled study evaluated the safety and effect on gut microbiota, and the mucosal inflammatory responses to a fermented milk in preterm infants. Preterm infants with a gestational age (GA) ranging from 30 to 35 weeks and whose mother chose formula feeding were enrolled during their first three days of life. Both parents provided informed written consent. Infants were randomly assigned to receive either the fermented preterm formula (FPF) or, as a control, a formula adapted for preterm infants (PF). The PF was formulated to meet the nutritional needs of preterm infants. The FPF was identical, except for a manufacturing process including a fermentation step with two probiotic strains, Bifidobacterium breve C50 and Streptococcus thermophilus 065, inactivated by heat at the end of the manufacturing process. This process conferred a probiotic/prebiotic activity.For each neonate, background information about the pregnancy and neonatal parameters were collected. Anthropometric parameters (weight, height, head circumference); gastrointestinal tolerance parameters (abdominal distension, gastric residuals, rectal bleeding, NEC); drug administration; and intake of formula and mother's milk were recorded twice a week until discharge. Stools were collected twice a week from diapers for microbiological analysis and measurement of fecal inflammatory markers. All samples were immediately stored at -80°C.

Inclusion Criteria:

• Preterms with gestational age ranging from 30 to 35 weeks
• Eutrophic
• Formula feeding

Exclusion Criteria:

• Malformation or metabolic disease
• Newborns whose parents did not provide informed consent
• Contraindication to enteral feeding