I think I've completely nuked my daily post quota today - the dangers of having a day off work. Nevermind.
Couple (actually several) of points,
1) Don't try anything in relation to using potassium permanganate as in my post above, in itself it's also toxic. I was wondering if anyone with the right knowledge could suggest a way that it could possibly be used as a treatment or just simply tell us that it's a definite no-go.
2) As your axolotl is now in the fridge - you should work on decontaminating your tank. I would recommend changing all of the water, siphon it all out and replace all of it with fresh dechlorinated water. And then over the next week or so do some very large water changes for good measure. You might be able to avoid the need to re-cycle your tank if you happen to own any fish who could live in there temporarily in order to keep the cycle going. That way your tank will be ready for Axel to go back in if he recovers or if the worst happens and you decide to start again with another one then you will have a tank ready to receive it.
3) At the very least I would try to educate the fish shop owner who sold you the axolotl, the pellets and the 'ichex' (or whatever it was called)
4) You should try to determine what caused the infection in the first place. How big is your tank? What temperature is the water? Do you have a water parameter testing kit? They are expensive but an infinitely better investment than bad medicine. Bad water chemistry could have allowed the infection to take hold and a water testing kit will allow you to monitor what's going on in your tank. I'm quite suspicious of the pellets you have been using, malnutrition may have caused your axolotl to become ill.
5) It's a shame you had such awful advice for looking after Axel, if he doesn't make it I personally would highly recommend starting again after you have thoroughly researched on here and on the
www.axolotl.org website.