I dealt with chronic ear infections with my Mastiff Buddy
He had surgery also and it corrected one ear but the damage to his other was too extensive and he would develop ear infections frequently. I was given this from someone who had the same problem it works and is inexpensive. It cut down the amount of infections he got by half. Let alone the cost but the pain he experienced was heartbreaking. I will say the best antibiotic he got was baytril for them, drops and pills. Here is the link to it I have posted it before and you can get everything at the pharmacy ask the pharmacist for the Genetian Violet.