Tiger Salamander with huge open wound on abdomen

I've had my tiger salamander for about a year and a half with no issues. Long story short, I have noticed that he has not been interested in food in a while and has shown abnormal behavior. I took him to the vet today and he has a large open wound (muscle is exposed) underneath him, starting right below his neck and going down to around where his front legs are. He also has a small patch of missing skin near one of his back legs, and a couple smaller wounds on his tail.

He absolutely HATES being picked up, he is almost always covered in dirt when I see him, and there is nothing in his enclosure that could cut him. Because of this I haven't seen underneath him in a really long time so I had no idea. The vet thinks it is an infection and I have oral medications, a topical ointment, and something to soak him in, so hopefully it all works.

I just wanted to know if anyone else has experienced anything like this with their salamanders??? And is there a good chance of him recovering ok or am I being too optimistic? He is still able to move around and has dug himself underground a few times (he is in a tank with only wet paper towel now though). I'm hoping for the best, and I will always make sure to check him over periodically in the future. But I'd appreciate anyone else's opinions or past experiences.

*** I did not attach a picture because it's pretty graphic looking =/ ***

I'm so glad you had a vet to take him to. Without knowing the cause, and also such an extensive wound, I wouldn't be hopeful, but you are trying your best!! Good luck!!