A 32 year old male, Kallu, who recently visited a sea coast presented with ulcer over the left leg. The probable cause is –
**Core Concept**
The probable cause of Kallu's ulcer is a bacterial infection resulting from exposure to seawater, specifically involving a marine bacterium that produces exotoxin.
**Why the Correct Answer is Right**
Kallu's exposure to the sea coast likely led to exposure to _Vibrio vulnificus_, a Gram-negative bacterium that thrives in saltwater environments. This bacterium produces a potent exotoxin that causes necrotizing soft tissue infection. The infection can lead to severe ulcers, particularly in individuals with compromised immune systems or those who have open wounds. The toxin works by damaging skin and underlying tissues, leading to necrosis and ulcer formation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it doesn't specify a bacterium that is commonly found in seawater and associated with necrotizing ulcers.
**Option B:** This option is incorrect because it implies a fungal infection, which is less likely to be caused by exposure to seawater.
**Option C:** This option is incorrect because it suggests a viral etiology, which is not commonly associated with necrotizing ulcers caused by seawater exposure.
**Clinical Pearl / High-Yield Fact**
When assessing patients with ulcers, especially those with recent exposure to seawater, it's essential to consider _Vibrio vulnificus_ as a possible cause. Prompt recognition and treatment can prevent severe complications.
**Correct Answer:** D. _Vibrio vulnificus_