Listeria is passed from Mom to baby in-utero and can be a severe sepsis in
both. I hope the baby is on antibiotics.  I have never heard of growing it
from milk! Why was the milk cultured?  Herpes Type I is the common facial
herpes ("cold sores") but can be found other places.  Again, in a lethargic
baby, I hope the infant is on acylovir!
The whole thing doesn't fit together.  Talk to the Neonatologist.
Nancy Wight MD
Neonatologist