Others with more experience in this area can weigh in on internal medications, but I'd honestly also start topical treatment with a serious but totally safe substance like Hypochlorous Acid. I would immediately order 0.2% strength hypochlorous acid and soak it in it. It is completely safe, and indicated for infections. I've never heard a single bad thing about it. In terms of wound infection protocols for humans and from what I am told veterinary is 2 minute exposure minimum, but ideally 10-15 minute exposure, ideally with immersion in it, or at the least
You can make your own Hypochlorous of varying strength by getting a machine. I like 0.3% for heavy infection treatments. A machine like this is priceless for around the house, cleaning, wound treatment, etc.
https://www.amazon.com/Eco-One-Porta...machine&sr=8-5
At the very least, you can order Cleansmart. It's all the same - hypoclorous acid, and cleansmart is extremely pure. We've used it for wound treatment for many years, but now generate our own. This is the same stuff doctors, dentists, and vets use and often sell in their offices.
https://www.amazon.com/CleanSmart-Su.../dp/B011AJRJZI
You can even combine treat with Betadyne between Hypochlorous without issue. I was able to stop a staph infection in my rescue in just a 24 hour period with full remission and healing activity using this combination to strike it fast. Generally, I'd do hypochlorous during the day, and Betadyne before bed so it stays on with the staining. My 2 cents.