What Causes Yellow Ear Drainage?

My daughter has been battling er infections her whole life. She had 6 tube surgeries with the last 2 sets as butterfly tubes. Her ear was perforated a year ago and never healed . Since she went to florida in august she got an ear infection. Months of antibiotics . We culture back said pseudomonas went on 20 days of levaquin 1000 mg per day . Still tons of yellow drainage coming out of her ear . I read cerebral fluid is clear . This last culture said negative in the culture .. Now we are doing a catscan ? But he is not telling me what he is looking for ? Everything I have read says yellow fluid is infection ? Any ideas ?