Fatal neonatal listeriosis following L. monocytogenes horizontal transmission highlights neonatal susceptibility to orally acquired listeriosis

We report a case of fulminant fatal neonatal listeriosis due to horizontal transmission of Listeria monocytogenes (Lm) in a neonatal double room. Genomic analyses reveal a close genetic relationship between clinical isolates, supporting cross-contamination. Oral inoculation experiments in adult and neonatal mice show that neonates are susceptible to a low Lm inoculum and that this susceptibility results from the immaturity of the neonatal gut microbiota. Infected neonates should therefore be isolated for as long as they shed Lm in their feces to avoid horizontal transmission and its dire consequences. [Display omitted] •Transmission of Listeria monocytogenes can occur between two neonates•Neonates are susceptible to a low Listeria monocytogenes oral inoculum•Gut microbiota immaturity contributes to neonatal susceptibility•Infected neonates should be isolated as long as they shed Listeria in their feces Charlier, Noel, Hafner et al. report a case of fulminant fatal neonatal listeriosis due to horizontal transmission of Listeria monocytogenes (Lm). Mouse oral inoculation experiments show that neonates are susceptible to a low Lm inoculum and that this results from the immaturity of the neonatal gut microbiota.