This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasitology Pa 1 (Protozoology), Subject name: Microbiology
A person having diarrhea of six month duration. Acid fast organism of size 10 micron are found in stool. Most likely cause is: 
Select and explain. 
A. Cryptosporidium, B. Isospora, C. Cyclospora, D. Giardia
C: Cyclospora
Answer: C: Cyclospora 
Explanation: Most likely causative organisms in this condition are coccidian parasites which include Cryptosporidium Isospora Cyclospora Size of oocyst in these organisms are Cryptosporidium -4-6 micron Cyclospora - 8-10 micron Isorpora - 23-36 micron Oocysts of these organisms are acid fast Cyst of giardia is not acid fast