A New C Diff Antibiotic
OPT-80 (or “PAR-101” or “Difimicin”)
According to PipelineReview.com and Optimer Pharmaceuticals, there may be a new drug coming out that “may eradicate C. difficile selectively,”  which could be a huge breakthrough in the treatment of Clostridium Difficile infections.
This drug is fantastic news for people suffering from multiple relapses.
The makers of the new drug say: “We believe that OPT-80 offers advantages over current treatments due to its demonstrated activity against C. difficile, low rates of recurrence, evidence of low C. difficile resistance, minimal systemic exposure, limited disruption of normally occurring gastrointestinal bacteria and convenient dosing regimen.” 
OPT-80 “targets” C Diff
According to Optimer Pharmaceuticals this drug may work against some gram positive bacteria, but not against gram negative bacteria. The idea is that if it only works against some gram positive bacteria then surely there will be many other good bacterias left behind still when you finish a round of this drug someday.
The exciting part of having good bacteria left over after you finish your antibiotics is that researchers believe that the good bacteria can “win out” and outgrow C Diff. So, you have a good environment in your gut, rather than a world ruled by the toxin-producing C Diff.
So, in theory it looks very promising. It is still not approved by the FDA for prescription against C Diff, but possibly after more phase II and III trials are completed it will be.
For a brief list of what worked for me see What Works.
Why relapses occur with C Diff
A likely cause of relapses is that the antibiotic (metronidazole or vancomycin) used to kill the C Diff infection also kills off all of the beneficial or normal bacteria in the GI tract. After 10 days or so, pretty much all bacteria is dead, leaving quite a vacuum to fill after antibiotics are finished.
C Diff creates spores to reproduce. These spores can last a very long time in many environments. So, although the antibiotic kills most or all of the active bacteria, it doesn’t necessarily kill all of the spores. Time goes by while you think things are good for a few days and the spores are amazingly ready to “grow up” into active bacteria again. Now, you are back where you started and it’s time to start antibiotics again.