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 monocyto-genes (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.

Automated summary

We present a case of fulminant neonatal listeriosis caused by horizontal transmission of Listeria monocytogenes (Lm) in a neonatal double room. Genomic analysis demonstrates a close genetic relationship between clinical isolates, supporting the idea of cross-contamination. Oral inoculation experiments in both adult and neonatal mice show that newborns are susceptible to a low Lm inoculum due to the immaturity of their gut microbiota. Therefore, infected neonates should be isolated until they stop shedding Lm in their feces to prevent horizontal transmission and its severe consequences.