# Tracing the early bacterial settlers in preterm and very-low birth-weight infants: first report of microbiota dynamics in South American neonates

## TL;DR

This study explores the gut microbiota of very-low birth-weight infants in South America and finds that antibiotics strongly influence early microbial development.

## Contribution

First report of microbiota dynamics in South American neonates and the impact of antibiotic exposure on microbial composition.

## Key findings

- VLBW infants show high abundance of Klebsiella pneumoniae and Escherichia coli.
- Microbial diversity increases over time with Bacteroides and Veillonella becoming more abundant.
- Prolonged antibiotic use increases abundance of specific bacterial species like Klebsiella and Enterobacter.

## Abstract

Mortality in very-low birth-weight (VLBW) infants accounts for up to 50%–70% of the neonatal mortality and up to 25%–30% of infant mortality. Despite the global increase in survival rates, this population remains at heightened risk for developing long-term neurodevelopmental delays, chronic lung disease, malnutrition, and visual and hearing disabilities. The gut microbial composition of VLBW differs from full-term infants and is typically dominated by pathobionts. In this study, we characterized the bacterial composition of the VLBW infant microbiota born at Pereira Rossell Children’s Hospital (academic, tertiary referral center) in Montevideo, Uruguay by sequencing the full-length 16S rRNA gene using Oxford Nanopore Technologies. We describe a high predominance of Klebsiella pneumoniae and Escherichia coli in these infants. By sequencing stool samples from two time points, we show that the microbial community diversity increases over time with a higher relative abundance of Bacteroides and Veillonella. Moreover, we describe the effect on the microbial composition of long antibiotic exposure. Different species of the Klebsiella genus, along with Escherichia coli, Enterobacter cloacae, Citrobacter freundii, and Veillonella parvula were observed at a higher relative abundance in patients with more than 5 days of antibiotic treatment. Taken together, our findings shed light on the development and establishment of microbial communities in early-life microbial communities in South America. Our results point to postnatal antibiotics as a major factor orchestrating this process. The integration of microbial community health considerations into preterm clinical care is crucial for improving long-term infant development.