- Stool culture for enteric bacterial pathogens, stool exam for ova and parasites, stool exam for cryptosporidia, stool exam for AFB.) Colitis that is so severe that it would be against the patient's best interest to be treated with placebo for 2 weeks prior to being eligible to receive ganciclovir (DHPG) on a "compassionate" use basis. Patients with a colitis of this severity should be treated with DHPG on "compassionate" use basis.