In my haste and excitement, I forgot to address the context of the
original post--- can strep B be passed through the breastmilk?  My post
was not meant to be a commentary on this question, as I don't know the
answer. In fact, my impression is that baby more likely picks it up
during vaginal birth; at any rate,  mom and/or babe seem to develop
symptoms a few days to a couple of weeks after delivery.

BUT--- what IF the mom transmitted it via the milk?  By the time we
figure this out, baby has already been exposed, right? Like so many other
similar scenarios, it makes sense to me to treat both mom and baby
together and continue nursing so that baby does not lose the additional
immune help, or wait at most a couple of days for mom's antibiotic to
kick in.

Again--- If a mom presents with bilateral mastitis, I'd send baby right
in whether or not he is symptomatic, as this is one dangerous organism
that can kill before you figure out something is really wrong. JMHO

-Lisa Marasco, BA, IBCLC