We are also going through this, but thankfully Day-z is doing great.
Started off last Friday, i came home quite late and in her room was a smell of blood. Could not see anything. Later when stroking her, i discovered blood under her chin - the fur was quite soked and the blood was hard. Next morning i took her to the vet. They examined her and shaved her chin and half her face, and took a sample from the wound site. They gave me spray and antibiotics.
Today I spoke to them, and the test results are back. 4 kinds of bacteria, 3 of which are handled by the existing antibiotics and 1 which is not. So, she is now on SMZ-TMP as well.
$300 later and we are on our way to health.
The very annoying thing is, i think this started when she came back from being bathed at the vets with wet ears - i thought nothing of it, but that was Wednesday and it seems like the timing fits perfectly.
Shaved bits are all healed now, but she is scratching and biting elsewhere, hopefully this new medicine will help her with that.
Good luck all