Rudy might need an examination of his ears while he's sedated. You vet can look for foreign bodies in his ears, take some samples for lab testing, and then flush the ears really well. Here are some additional discussions of ear problems.
You may also want to have a "resistance screen" done (I don't know the real name), where they check which antibiotics the bacteria are resistant to (if it's a bacteria problem). That way you can make sure you are using the right antibiotic to knock out the infection.
We had to do this for one of my basset wannabees to get rid of the infection
Obviously, if it's not a bacterial infection, then you will need to take other action.
If he does it is VERY difficult to permanently clear up the ears without addressing the allergies first. I was not able to clear up Webster's ears until I first was able to find a diet he was not allergic to.
I've had great success with the Blue Power (not Powder) Ear Treatment. I don't have the recipe handy, but if you google it it will turn up.