A case of drug-resistant staphylococcal para-aural abscess treated with photodynamic therapy in a West Highland White Terrier presenting with chronic otitis and craniomandibular osteopathy.

A 10-year-old canine with chronic unilateral otitis and a history of unsuccessful systemic and topical antibiotic treatments was referred. A computer tomography scan (CT scan) revealed unilateral chronic otitis with calcification of the ear canal, abscessation and fistula. On bacterial culture a Staphylococcus pseudintermedius sensitive to pradofloxacin was isolated. Systemic treatment with pradofloxacin, 3 mg/kg per os once daily, improved the infection and the dog had total ear canal ablation and bulla osteotomy performed. After one month, despite antibiotic treatment new fistulas developed in the same area. Bacterial culture revealed an drug-resistant S. pseudintermedius sensitive only to rifampicin. Under general anesthesia, the area was cleaned with 0.5% saline solution and 1 mL of indocyanine green (Emundo®, A.R.C.) was injected into the fistulas. A treatment with diode laser (A.R.C. Laser 810 nm, GmbH, Nurnberg, Germany) of four cycles 500 mw for 30 s, with a dosage of 50 J/cm2 in the effected area was performed. No antibiotic was administered and one week later, 50% of the fistulas were closed with a significant improvement of the patient's clinical condition. Cytology and bacterial culture were negative 72 h after the treatment. Total recovery occurred after two weeks. Photodynamic Therapy(PDT) is a promising antibacterial technique in case of localized refractory bacterial infections.