Hi All,
Just anecdotally:
My son caused me the worst case of maserated nipples my LC had seen in years.
 I ended up with Bi-Lateral Mastitis as a result.  However, I NEVER had
plugged duct in both breasts.  Only one plugged duct in the left breast that
resolved a week before the mastitis showed up.  Our theory was that the
nipple damage allowed the bacteria into the breast tissue, and caused the
mastitis.
Now, I was under the impression that mastitis was an infection of the breast
tissue, not neccessarily the milk ducts.  Was I wrong?

Jay

PS, I had badly damaged nipples that took a full 2 months to heal before we
could put baby back to breast.  The mastitis took 4 months to finally clear,
and that was while I was on 3 different antibiotics (Not all at the same time
of course).  Any ideas as to why it was so resistant to treatment?