A 52-year-old man presents to the clinic with severe left ear pain, purulent discharge, and worsening headache for the past week. He has been experiencing fever and progressive difficulty chewing due to pain radiating to the temporomandibular joint. He has tried over-the-counter analgesics and topical ear drops without relief. His medical history includes poorly-controlled type 2 diabetes, hypertension, and hyperlipidemia. He takes metformin, glargine insulin, lisinopril, and atorvastatin. He does not smoke cigarettes but drinks alcohol socially. His temperature is 101.6°F (38.7°C), blood pressure is 132/78 mmHg, and heart rate is 94 beats/min. Physical examination reveals tenderness over the mastoid process, swelling around the ear, and granulation tissue in the external auditory canal.
Which of the following is the most likely causative organism?
The correct answer is:
C) Pseudomonas aeruginosa
Malignant otitis externa is a severe necrotizing infection seen in elderly patients or patients with diabetes, most commonly caused by Pseudomonas aeruginosa. The presence of granulation tissue, severe pain, and systemic symptoms strongly suggest this diagnosis.
Answer choice A: Aspergillus fumigatus, is incorrect. Aspergillus can cause fungal otitis externa but is less frequently implicated in necrotizing or malignant cases.
Answer choice B: Candida albicans, is incorrect. Fungal otitis externa is typically caused by Candida or Aspergillus, but it does not present with such aggressive symptoms.
Answer choice D: Staphylococcus aureus, is incorrect. S. aureus may cause skin infections but is not the primary pathogen in malignant otitis externa.
Answer choice E: Streptococcus pneumoniae, is incorrect. S. pneumoniae is more commonly associated with otitis media rather than otitis externa.
Key Learning Point
Malignant otitis externa is most commonly caused by Pseudomonas aeruginosa, especially in patients with poorly-controlled diabetes.
