One of the most common causes of diarrhea in HIV infected patients is cryptosporidiosis. Which of the following is the method used for diagnosis of cryptosporidiosis in fecal matter?

Cryptosporidiosis is a protozoan which is most commonly involved in the pathogenesis of diarrhea in HIV infected patients. The cysts for cryptosporidiosis are best demonstrated by Ziehl-Neelsen stain of fecal mater. Other impoant clinical laboratory tests for stool are summarized as follows. Analysis of Stool: 1. Physical examination for color, frank blood, undigested food, worms etc. 2. Chemical examination of Reducing substance for lactose intolerance, of Fecal fat for malabsorption syndrome, of Protein content for Protein losing enteropathy. Occult blood test. 3. Direct light microscopy for demonstration of RBC, WBC,Crystals and Ova of different types of helminths. Demonstration of protozoan like E. histolytica and Giardia. 4. Culture of stool for Salmonella, Shigella, Campylobacter, etc. 5. Assay for demonstration toxins in stool in cases of patients suffering from Pseudomembranous colitis (toxin of Cl. difficile). 6. ELISA- This test it is able to find viral antigens (Rotavirus) as a causative agent for infantile diarrhea. 7. Electron microscopy for demonstration of virus (Rotavirus). 8. Gram/Z-N stain. Z-N staining of stool smear is highly diagnostic for demonstration of Cryptosporidiosis (protozoa) responsible for diarrhea in an immunocompromised host (AIDS). Ref: Brooks G.F. (2013). Chapter 46. Medical Parasitology. In G.F. Brooks (Ed),Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.