Childhood malnutrition affects physiology and development. It increases infection rates, which may not present clinical signs in severe cases. The World Health Organization recommends prophylactic treatment with cotrimoxazole (SXT) and nutritional recovery to overcome this issue. This treatment is controversial, since evidence of a reduction in morbidity and mortality is not a consensus and could induce the development of antibiotic-resistant bacteria. Moreover, the impact of using this wide-spectrum antibiotic on gut microbiota in a critical period of development, and weakness is unknown. To understand how SXT prophylaxis could affect gut microbiota in undernutrition, we induced protein–energy undernutrition (PEU) in weaning C57BL/6 mice for three weeks and treated animals with SXT for two weeks. Using 16S rRNA gene sequencing, we compared the taxonomic composition and metabolic pathways of control mice, animals submitted to undernutrition (UND), treated with SXT, or undernourished and SXT treated (UND + SXT). We identified that UND mice had a significant increase in predicted pathways related to metabolic syndromes later in life. The prophylactic SXT treatment alone resulted in a significant loss in community richness and beta diversity. Furthermore, we identified the reduction of three genera in SXT treated mice, including the butyrate producers Faecalibacterium and Anaerotruncus. Both UND and double challenge (UND + SXT) resulted in a reduction of the amino acid’s biosynthesis pathway related to cell growth. Our results show that the SXT prophylaxis of young mice during an undernourishment period did not re-establish the undernourished microbiota community composition similar to healthy controls but induced a distinct dysbiotic profile with functional metabolic consequences.

Mother's own milk (MOM) is the most complete nutritional resource for newborns. In cases where mothers are unable to produce sufficient milk or cannot breastfeed, the preferred alternative is pasteurized donor human milk (PDM), which is routinely provided by human milk banks. PDM offers a superior range of nutritional and immunological elements compared to any commercially available formula. However, to ensure biosafety, PDM undergoes pasteurization, a process that inactivates commensal microbiota and reduces certain bioactive compounds. This study presents a protocol designed to restore the microbiota of PDM using MOM as a microbial source, adapting the approach to a real-world clinical setting. The protocol was implemented in a clinical trial conducted at a maternity hospital and its associated human milk bank, with the aim of providing personalized donor milk to preterm infants whose mothers cannot produce sufficient milk. The methodology involves inoculating PDM with 10% of MOM, followed by incubation at 37 °C for 4 h. Microbiological analysis demonstrated successful bacterial growth in the inoculated milk (IM) post incubation, with the microbiota profile of the reconstituted milk (RM) closely resembling that of MOM, indicating effective microbiota restoration. These results suggest that the reconstitution protocol is feasible for implementation in neonatal care, with the potential to enhance the nutritional and immunological quality of PDM, thereby supporting the health and development of non-breastfed newborns.

Mother's own milk (MOM) is the most complete nutritional resource for newborns. In cases where mothers are unable to produce sufficient milk or cannot breastfeed, the preferred alternative is pasteurized donor human milk (PDM), which is routinely provided by human milk banks. PDM offers a superior range of nutritional and immunological elements compared to any commercially available formula. However, to ensure biosafety, PDM undergoes pasteurization, a process that inactivates commensal microbiota and reduces certain bioactive compounds. This study presents a protocol designed to restore the microbiota of PDM using MOM as a microbial source, adapting the approach to a real-world clinical setting. The protocol was implemented in a clinical trial conducted at a maternity hospital and its associated human milk bank, with the aim of providing personalized donor milk to preterm infants whose mothers cannot produce sufficient milk. The methodology involves inoculating PDM with 10% of MOM, followed by incubation at 37 °C for 4 h. Microbiological analysis demonstrated successful bacterial growth in the inoculated milk (IM) post incubation, with the microbiota profile of the reconstituted milk (RM) closely resembling that of MOM, indicating effective microbiota restoration. These results suggest that the reconstitution protocol is feasible for implementation in neonatal care, with the potential to enhance the nutritional and immunological quality of PDM, thereby supporting the health and development of non-breastfed newborns.