Any questions: Treating resistant otitis externa

What is the treatment for “resistant” otitis externa due to Pseudomonas aeruginosa? My patient has received topical treatment with gentamicin, polymyxin B. ciprofloxacin, 5% acetic acid, 4% aluminium acetate, ceftazidime, meropenem, and intravenous treatment with ceftazidime, and ciprofloxacin. She has partially responded to these but subsequently relapsed, with bilateral green discharge and eczematous skin just around the external ear canal. The ear drums have remained intact and the rest of the ear, nose, and throat examination is normal. The …