Tyson,
My neuro just advised me 2 weeks ago that a new med had been added to the forbidden list, I think it's Keflex...
I goggled for some references but all I could get was:

Antibiotics: Infections: Merck Manual Home Edition
KEFLEX. Mainly skin and soft-tissue infections .... Worsening of symptoms in people with myasthenia gravis (possibly fatal). Vancomycin Some Trade Names ...
www.merck.com/mmhe/sec17/ch192/ch192a.html

without beeing able to get to the point where the interaction was mentioned...
Maybe someone else would be more successful?
Maurice.