I hope one of the physicians responds to this. I am more than a bit concerned
about the flawed logic in the case you described.
>>The surgeon severed a duct during the surgery, was unable to reattach it,
and so tied it off. <<
I am assuming that the redness and swelling is related to the same duct.
After just going through sepsis myself I can understand the reason the dr.
wants the antibiotics (just in case).
From your comments:
 >>  was concerned that bacteria from the child's mouth would infect the
surgical site. <<
It seems that the surgeon may have decided that it IS mastitis because mom is
STILL breastfeeding on that side and not looking at the most obvious
cause--the severed and tied off duct.  If there are no systemic symptoms eg.
fever, joint pain, flu symptoms etc.  the assumption of mastitis is not
logical.
I have seen a lot of this type of problem in moms that have breast surgery. A
severed  duct will continue to be red and painful until it involutes. This is
a localized reaction to the backup of milk. Milk in the breast should be
sterile--provided no bacteria were introduced during the removal of the
galactocele.
Marie Davis, RN, IBCLC