Oh my goodness, your poor husband is going through the wringer! And you! Shaking my head with the misadventures of the missing and mislabeled specimens! Don’t you wonder where they went? …a little humor. But, aw, my heart goes out to both of you. It’s so stressful!

C-diff is nothing to mess around with, as you’re learning. Vancomycin should help turn that around but when he’s so weak it is really a rough to get through. It’s a relief to hear his blood numbers are going up. That should help fortify his fighting capacity for infections. Were you given any instructions for how to avoid this for yourself?
A couple of good sites to help you:
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https://www.clorox.com/learn/c-diff-cleanup-how-to-prevent-spread-of-c-diff-at-home/
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https://www.c-difficile-treatment.com/infection-control/
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https://www.mayoclinic.org/diseases-conditions/c-difficile/symptoms-causes/syc-20351691
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It’s encouraging that he’d been doing really well up to this point. If I counted correctly I think he’s around day 103-ish?? Passing that 100 day threshold is a milestone marker for progress. Generally after that time any GVHD tends to come on slowly and what does pop up gets nipped in the bud with a steroid burst. It’s like stomping out little fires. After a while, things usually start settling down with fewer fires.

I’m assuming he’s still on his anti-rejection med and all the other handful of pills for a while.
The anti-rejection pills are immunosuppressive to keep his new immune system from attacking his body. Graft=new cells vs Host=body. So once he’s able to start the slow taper from the immunosuppressant he’s taking, his immune system will start to mature and become more robust. But right now it’s a fine art of ‘tweaking dials’ until his new cells and body start playing nicely together.
It’s really tricky getting that balance just right. If he’s showing signs of GVHD then his doctor will keep him on the tacrolimus or whatever he’s taking because lowering it might allow for more GVHD. However, in order for his body to be able to fight infections, it’s in his best interest to lower the immunosuppressants. It’s a catch 22.

Having a clean bone marrow biopsy is news to celebrate. ☺️ I think once this C-diff gets under control you’re going to see your husband make some positive improvements. Right now he’s not getting much nutrition from what he’s eating so that is going to cause weight loss along with crazy fluctuations in his electrolytes and hydration. It’s really important that he gets in a lot of water during the day, pedialite or Gatorade or whatever his doctor recommends to keep hydrated/electrolytes balanced. If he’s not already eating yogurt, try to encourage your husband to have some Activia to rebalance the gut. There are probiotics he can take but some dissolve too quickly and don’t get absorbed. I didn’t have C-diff but early on with all the chemo and side effects from the transplant, Activia was palatable and really helped with all the antibiotic disruption. (Take a couple hours before or after the antibiotics). I used to stir in a teaspoon of ground flax for some fiber too.

Sorry, this got a little lengthy. I tend to think we’re sitting around the kitchen table talking…we need more coffee! ☺️
Your husband will get through this nasty business and become stronger soon. As my mom used to say, “This too shall pass.”
How is your husband coping mentally with this little setback?