I agree with Bob_b. Most fungal and bacterial infections in crocodilians stem from poor water conditions and secondary infections. See my post above regarding "white spot on caiman" by tbone21.
Since you mentioned that this abscess is located on the animal's face and it is missing teeth, you should not rule out the possibility of mouth rot (stomatitis). Stomatitis can become extremely necrotic, killing large amounts of tissue, muscle and skin. I have received two or three iguanas that had such horrible cases of mouth rot that tissue was completely absent; leaving the teeth and jaw (what remained of them) totally exposed. One of them with a head about the size of a tennis ball had an abscess protruding from it's lower jaw the size of a golf ball and it's bottom jaw bone was rotted in half.
It sounds like the gator that you have doe's not have an infection as serious as the cases I just stated, however it should receive a professional examination by a qualified vet.
Bill
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