Priming immunity at the beginning of life (PRIMAL)

The PRIMAL study is an investigator-initiated, multicenter, double-blind, placebo-controlled, group-sequential randomized clinical trial involving 618 preterm infants born between 28 and 32 weeks of gestation.The primary aim was to evaluate the efficacy of a probiotic combination: Bifidobacterium longum subsp. infantis, Bifidobacterium animalis subsp. lactis (BB-12), and Lactobacillus acidophilus (La-5) in preventing colonization with multidrug-resistant organisms or highly epidemic bacteria (MDRO+), and in promoting a eubiotic microbiome composition resembling that of healthy full-term infants.Methods: MDRO+ colonization was determined using conventional culture methods from stool samples collected on day 30 of life. Microbiome composition was assessed via 16S rRNA gene sequencing of stool samples collected on days 3, 30, and 356.Results: MDRO+ colonization was observed in 37.4% of the probiotic group compared to 37.5% in the placebo group. However, probiotic treatment shifted microbiome composition toward eubiotic patterns typical of full-term infants. Notably, B. infantis demonstrated a high potential for environmental acquisition.Key publication: doi:10.1001/jamapediatrics.2024.2626