An elderly diabetic consults a physician because of severe earache. Examination demonstrates foul-smelling purulent otorrhea and a red mass lesion of the external ear canal. Biopsy of the mass demonstrates granulation tissue. Most likely causative organism is?
First, I need to recall the common infections in diabetic patients related to the ear. Diabetics are prone to certain infections because of their impaired immune response. The ear canal infection could be otitis externa. But the presence of a red mass and granulation tissue makes me think of something more specific.
Malignant otitis externa comes to mind. This is a severe, progressive infection that occurs in immunocompromised individuals, especially diabetics. It's usually caused by Pseudomonas aeruginosa. The symptoms include severe pain, purulent discharge, and granulation tissue.
Another possibility is a fungal infection, like Aspergillus, which can cause otomycosis. But that's more common in non-diabetics and might present with itching rather than severe pain.
The red mass could also be a cholesteatoma, but that's a non-neoplastic growth of skin in the middle ear, not an infectious cause.
So the key here is the combination of diabetes, granulation tissue, and Pseudomonas. Let me check the options. The correct answer should be Pseudomonas aeruginosa. The other options might be Candida, Aspergillus, or Staphylococcus, but those don't fit the clinical picture as well.
Wait, the options weren't provided, but based on the context, the most likely organism is Pseudomonas aeruginosa. The clinical pearl here is that in diabetics with malignant otitis externa, Pseudomonas is the main culprit. The granulation tissue is a hallmark of this condition. So the correct answer is Pseudomonas aeruginosa.
**Core Concept**
The question tests knowledge of *malignant otitis externa*, a severe infection in immunocompromised/diabetic patients caused by **Pseudomonas aeruginosa**, characterized by granulation tissue and purulent otorrhea.
**Why the Correct Answer is Right**
*Pseudomonas aeruginosa* thrives in the moist, acidic environment of the ear canal and exploits diabetes-related neutrophil dysfunction. It causes aggressive, necrotizing infection with granulation tissue due to chronic inflammation. The foul-smelling discharge and red mass (granulations) are classic signs, differentiating it from fungal or bacterial otitis externa.
**Why Each Wrong Option is Incorrect**
**Option A:** *Candida albicans* causes fungal otitis externa with itching and white debris, not granulation tissue.
**Option B:** *Staphylococcus aureus* is a common cause of acute otitis externa but lacks the severe systemic features and granulation seen here.
**Option D:** *Aspergillus* species cause otomycosis, presenting with pruritus and black fungal hyphae, not purulent otorrhea.
**Clinical Pearl / High-Yield Fact**
Never miss *Pseudomonas aeruginosa* as the causative agent in diabetic patients with malignant otitis externa—it can spread to the skull