Cyclosporiasis caused by Cyclospora cayetanensis is differentiated from Cryptosporidium parvum infection on stool examination by which characteristic feature?
- A Cryptosporidium oocysts are sporulated (contain sporozoites) when passed in stool, whereas Cyclospora oocysts are unsporulated ✓
- B Oocysts of Cyclospora are acid-fast and auto-fluorescent under UV light; those of Cryptosporidium are only acid-fast
- C Cyclospora is identified by modified Ziehl-Neelsen stain but not safranin stain, unlike Cryptosporidium
- D Both organisms are morphologically identical and can only be distinguished by PCR
Explanation
A key distinguishing feature: Cyclospora cayetanensis oocysts (8–10 µm) are excreted unsporulated in fresh stool and require days to sporulate outside the host, while Cryptosporidium parvum oocysts (4–6 µm) are already sporulated and immediately infectious when passed in stool. Both stain with modified acid-fast stain (variable pink), but Cyclospora oocysts also exhibit intense blue auto-fluorescence under UV epifluorescence microscopy, which Cryptosporidium lacks. The larger size of Cyclospora oocysts (8–10 µm vs 4–6 µm for Cryptosporidium) also aids differentiation. Trimethoprim-sulfamethoxazole treats Cyclosporiasis; nitazoxanide or paromomycin is used for Cryptosporidium.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.