A 30-year-old man with AIDS presents with chronic watery diarrhoea. Modified Ziehl-Neelsen staining of stool shows small round acid-fast oocysts of 4 to 6 micrometre size. Which drug provides effective therapy in this setting?
- A Metronidazole
- B Praziquantel
- C Nitazoxanide ✓
- D Chloroquine
Correct answer: C. Nitazoxanide
Explanation
Cryptosporidium parvum produces tiny acid-fast oocysts demonstrable on modified Ziehl-Neelsen stain and causes prolonged watery diarrhoea in immunocompromised hosts. Nitazoxanide is the only licensed drug with proven activity against cryptosporidiosis, though response is poor unless immunity is restored by antiretroviral therapy. Metronidazole has no activity against Cryptosporidium, praziquantel is an anthelminthic, and chloroquine is an antimalarial.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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