It's difficult to say without a stool sample whether he had it all along. All it takes to become an infection/invasion is an imbalance in intestinal flora in a compromised person.
I hope the vancomycin helps him quickly.
If your husband did have it previously and took the flagyl but stopped it, it's possible that's when it was able to become more prolific.
Whatever the reason, I do hope it helps him quickly. He'll have to have other stool samples to make sure it's gone...push that with the doc.
Keep us updated...it's good news that he knows what's going on.
I think you should be taking probiotics as well since you live intimately.
*Heather*Status: mini flare Dec 28... tapered to every 4th night
~diagnosed January 1989 UC (proctosigmoiditis)
~5ASA: Asacol (6 daily) + Salofalk enemas (increase for flares tapered to maintenance)
~Bentylol (dicyclomine) 20mg as needed
~Probiotic 3(Natural Factors Protec) bedtime + 1 (Primadophilus Reuteri) occasionally
~multi-digestive enzymes as needed ....zymactive 3 - 5x daily
~Ranitidine,Pariet (reflux) Effexor XR 75mg; Pulmicort/Airomir (asthma)
~URSO for PSC (or PBC) 500mg X 2 daily (LFTs back to NORMAL!!)
My doc's logic.. "TREAT (FROM)BOTH ENDS" worth it !!!