A vitreous aspirate from a case of metastatic endophthalmitis on culture yields Gram-positive round to oval cells, 12-14 m in size. The aspirate on Gram staining shows the presence of pseudohyphae. Which of the following is the most likely aetiological agent ?

**Core Concept**
The question requires the identification of a Gram-positive, round to oval organism that can produce pseudohyphae, which is a characteristic feature of certain fungal species. The presence of pseudohyphae in a vitreous aspirate suggests a fungal etiology for the endophthalmitis.

**Why the Correct Answer is Right**
The correct answer is likely a fungus that exhibits both yeast and hyphal forms, which is a characteristic feature of Candida species. Candida albicans is a common cause of endophthalmitis, particularly in cases of ocular trauma or surgery. The organism's ability to form pseudohyphae and produce biofilms contributes to its virulence and resistance to antimicrobial therapy. The presence of pseudohyphae on Gram staining is a key diagnostic feature of Candida species.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not match the description of the organism. While some Gram-positive cocci can be round to oval in shape, they do not typically produce pseudohyphae.
**Option B:** This option is incorrect because it is a Gram-negative organism, which does not match the Gram-positive staining characteristics of the organism in the question.
**Option C:** This option is incorrect because it is a Gram-negative rod, which does not match the Gram-positive staining characteristics of the organism in the question.

**Clinical Pearl / High-Yield Fact**
Candida endophthalmitis is a serious condition that requires prompt treatment with antifungal agents, such as fluconazole or amphotericin B. Early diagnosis and treatment are critical to prevent vision loss and other complications.

**Correct Answer:** C. Candida species.

✓ Correct Answer: C. Candida