Oh, I can well believe such an infection may be serious in a newborn. I just don't see it developing from a contact with intact skin that the baby can't even reach with its hands.

I had at least one baby advice book that suggested prechewing food for babies starting solids. Terrible advice for multiple reasons, but the one that especially got me is the likelihood of colonizing the baby's mouth with caries bacteria just as the first teeth were coming in.