Mapping the Neonatal Pathobiont–Resistome Interface Across Four Niches: A Narrative Review of Delivery Mode, Gestational Maturity and the Limits of Current Evidence

Cesarean section accounts for 21.1% of births worldwide and 13.4 million infants were born preterm in 2020, yet pathobiont carriage and resistance genes are usually reported separately, from stool alone. This review maps that interface across four anatomical niche groups (an evidence map rather than a demonstrated relationship), taking infants born at 32 + 0 to 36 + 6 weeks as the index stratum against term, very preterm and extremely preterm contrasts. Delivery mode is associated with community composition through at least two candidate mechanisms: substitution of the founding inoculum and failure of colonization resistance to be established. Umbilical inoculation at the point of care is treated as mode-independent. Strain sharing across compartments, shown in small series, suggests that single-niche sampling may capture the interface incompletely. Delivery-mode associations are reported less consistently at lower gestational maturity, although biological attenuation cannot be distinguished from differences in care exposure, statistical power and methodology. Within the literature reviewed here, delivery-mode colonization data were not identified for three of the four niche groups; no dataset reported the resistome of this band as a discrete stratum; and the largest intervention evidence base lies outside this population. Breastfeeding support and antibiotic stewardship are the practices best matched to the mechanisms identified.