Prenatal antibiotics reduce breast milk IgA and induce dysbiosis in mouse offspring, increasing neonatal susceptibility to bacterial sepsis

Antibiotics (Abx) are administered to 20%-30% of pregnant women, but their effects on neonatal immune development are poorly understood. We show that newborn mice born to Abx-treated dams are more susceptible to late-onset sepsis. This susceptibility is linked to lower maternal breast milk immunoglobulin A (IgA), neonatal fecal IgA, and IgA coating of intestinal bacteria, thus causing the translocation of intestinal pathobionts. Weaned young adults born to Abx-treated mothers had reduced IgA+ plasma cells in the ileum and colon, fecal secretory IgA (SIgA), colonic CD4