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

The gut microbiota of VLBW infants in Uruguay was characterized by high predominance of Klebsiella pneumoniae and Escherichia coli.

• Study conducted at Pereira Rossell Children's Hospital, an academic tertiary referral center in Montevideo, Uruguay.
• Full-length 16S rRNA gene sequencing was performed using Oxford Nanopore Technologies.
• This represents the first report of microbiota dynamics in South American neonates of this population.
• The microbial composition was described as dominated by pathobionts, consistent with the broader VLBW literature.

Microbial community diversity in VLBW infants increased over time, with higher relative abundance of Bacteroides and Veillonella at the second time point.

• Stool samples were collected at two time points to track longitudinal microbiota dynamics.
• Early samples showed dominance of Klebsiella pneumoniae and Escherichia coli.
• Later samples showed a shift toward higher relative abundance of Bacteroides and Veillonella.
• This temporal increase in diversity suggests a progressive maturation of the microbial community during the neonatal period.

Prolonged antibiotic exposure (more than 5 days) was associated with higher relative abundance of specific pathobiont species.

• Infants with more than 5 days of antibiotic treatment showed higher relative abundance of different species of the Klebsiella genus, Escherichia coli, Enterobacter cloacae, Citrobacter freundii, and Veillonella parvula.
• Postnatal antibiotics were identified as 'a major factor orchestrating' the microbial community composition.
• The effect of antibiotic exposure on microbial composition was analyzed as part of the two-time-point sampling design.
• Long antibiotic exposure was associated with persistence or enrichment of potential pathobionts rather than commensal colonization.

VLBW infant mortality accounts for up to 50–70% of neonatal mortality and up to 25–30% of infant mortality globally.

• Despite global increases in survival rates, VLBW infants remain at heightened risk for long-term complications.
• Complications include neurodevelopmental delays, chronic lung disease, malnutrition, and visual and hearing disabilities.
• The gut microbial composition of VLBW infants differs from full-term infants and is typically dominated by pathobionts.
• These epidemiological facts formed the basis for studying VLBW microbiota in a South American context.

This study provides the first characterization of microbiota dynamics in South American VLBW neonates.

• The study fills a geographic gap in neonatal microbiota research, which has largely been conducted in North American, European, and Asian cohorts.
• The integration of microbial community health considerations into preterm clinical care was highlighted as crucial for improving long-term infant development.
• Full-length 16S rRNA gene sequencing via Oxford Nanopore Technologies enabled high-resolution taxonomic identification.
• Findings point to the need for region-specific microbiota data to inform clinical practices in South America.