Preterm infant gut microbiome analysis and functional profiling. Credit: Nature Communications (2025). DOI: 10.1038/s41467-025-62584-2

Preterm babies with very low birth weight who received a probiotic alongside antibiotics had fewer multidrug resistant bacteria and a more typical gut microbiome, a new study shows.

The paper, published in Nature Communications, is the result of a trial testing probiotics among a group of 34 preterm babies born with a very low birth weight, under 1500g, representing around 1–1.5% of babies born around the world. The study sequenced gut bacteria from the babies during the first three weeks after birth.

The collaborative study was led by Professor Lindsay Hall and Dr. Raymond Kiu from the University of Birmingham found that among babies who received a probiotic treatment of a certain strain, including Bifidobacterium, alongside antibiotics, levels of typical bacterial strains associated with early-life gut microbiota were at levels typical among full-term babies, reducing both the abundance of antibiotic resistance genes and the number of multidrug-resistant bacteria in the gut.

There were lower levels of drug-resistant pathogens, including Enterococcus, associated with risks of infections and longer hospital stays. Babies who received probiotics also saw higher levels of certain positive bacteria found naturally in the gut.

Among babies who didn't receive probiotics, analysis of the gut bacteria found that while some differences occurred between those receiving antibiotics or not, both groups saw a dominant microbiome develop that included key bacteria (pathobionts) that can cause health problems, including life-threatening infections during the crucial period after birth, as well as in later life.

Professor Lindsay Hall from the University of Birmingham and a group leader at Quadram Institute Bioscience, and senior corresponding author of the study said, "We have already shown that probiotics are highly effective in protecting vulnerable preterm babies from serious infections, and this study now reveals that these probiotics also significantly reduce the presence of antibiotic resistance genes and multidrug-resistant bacteria in the infant gut. Crucially, they seem to do so selectively—targeting resistant strains without disrupting non-resistant strains that might be beneficial.

"In the context of the global AMR crisis, this is a major finding, especially for NICUs where preterm infants are especially vulnerable. Probiotics are now used in many neonatal ICUs around the UK, and the WHO have recommended probiotic supplementation in preterm babies.

"Our paper shows how beneficial this intervention can be for babies born prematurely to help them give their gut a kickstart, and reduce the impact of concerning pathogens taking hold."

Dr. Raymond Kiu from the University of Birmingham, first and co-corresponding author of the paper said, "Sequencing technology has now confirmed that probiotic Bifidobacterium rapidly replicates in the preterm gut during the first three weeks of life. Importantly, this successful colonization drives the maturation of the gut microbiota and is linked to a noticeable reduction in multidrug-resistant pathogens—pointing to its pivotal role in improving neonatal health.

"Our findings also shed light on the complex interactions between antibiotics, probiotics, and horizontal gene transfer (HGT) in shaping the early-life microbiome."

"We believe this research lays the groundwork for future studies exploring the role of probiotics in antimicrobial stewardship and infection control among preterm populations."

More information: Raymond Kiu et al, Impact of early life antibiotic and probiotic treatment on gut microbiome and resistome of very-low-birth-weight preterm infants, Nature Communications (2025). DOI: 10.1038/s41467-025-62584-2  Journal information: Nature Communications