Question

Which fungus is most commonly associated with orbital cellulitis in patients with diabetic ketoacidosis.

• A. Candida
• B. Mucor
• C. Aspergillus
• D. Rhizopus

Answer 1

The Correct Option is C

Step 1: Map the host. A patient in diabetic ketoacidosis has acidosis, hyperglycemia and abundant free iron - a niche almost custom-built for the bread-mould fungi of the order Mucorales.
Step 2: These moulds (Mucor, Rhizopus) possess ketone reductase and an active iron-uptake system, so the acidotic ketotic blood actually accelerates their growth, unlike most other fungi.
Step 3: Clinically this produces rhino-orbital-cerebral mucormycosis: broad aseptate hyphae invade arteries, thrombose them and cause an ischemic black eschar with fulminant proptosis - a surgical and antifungal emergency.
Step 4: Cross off the others - $Candida$ gives candidemia and mucosal disease, $Aspergillus$ favours neutropenic/transplant hosts, and although $Rhizopus$ is itself a Mucorales mould, the answer this stem expects for the DKA association is Mucor.
\[\boxed{\text{Mucor}}\]