Q: What is the differential diagnosis?
A: Opportunistic pathogens such as disseminated Mycobacterium avium complex (MAC), PCP, and cytomegalovirus (CMV), should be considered, though PCP does not typically cause GI disease. He is also at risk for Entamoeba histolytica, Dientamoeba fragilis, Blastocystis hominis, Giardia lamblia, Campylobacter jejuni, Shigella spp, Salmonella spp, C. difficile, syphilis and herpes simplex virus. Because of recent travel to Mexico, Escherichia coli, Vibrio parahaemolyticus, Yersinia spp, rotaviruses, and Norwalk-like viruses are also in the differential. Additionally, this inmate could have diarrhea and wasting from HIV itself. It is not likely that Nelfinavir is causing his diahhrea as he tolerated this drug for nine to ten months and only recently developed diarrhea. Though the Nelfinavir may not be the cause of the diarrhea, it may be aggravating it.
Q: What tests should you perform/order?
A: Stool samples should be sent for WBCs, to help differentiate inflammatory from non-inflammatory causes of diarrhea (history of watery as opposed to bloody diarrhea suggests non-inflammatory). Stool samples should also be sent for culture for enteric pathogens, smear for ova and parasites, Giardia antigen, Clostridium difficile toxins A and B, and acid-fast bacilli (AFB) smear and culture. Tests for ova and parasites, C. difficile toxins, and smears for AFB should be repeated twice, as it often takes multiple evaluations before some of these pathogens are detected. Blood should be sent for AFB culture and routine bacterial culture. If there is no temporal association of the onset of diarrhea with antiretroviral therapy and the stool and blood studies are negative, the next step in the evaluation is a colonoscopy. The highest yield for colonoscopy is typically in patients with fever, weight loss, and a CD4 count of fewer than 200 cells/mm3.
Concentrated exam of the stool showed many cysts of Giardia lamblia and Entamoeba histolytica. This diagnosis should be reported to the local public health department. Many Entamoeba coli cysts, many Endolimax nana cysts, and moderate Iodamoeba butschlii cysts were also seen. On auramine stain, moderate cryptosporidia were detected.
Q: What treatment(s) should you offer this inmate? Are there drug-drug interactions to consider?
A: Endolimax nana, Entamoeba coli, and Iodamoeba butschlii are nonpathogenic commensals and as such require no treatment. They are however markers of exposure to human feces and are often found in patients who are also infected with pathogenic organisms. Giardia and Entamoeba histolytica can cause invasive disease and should generally be treated. The drug of choice for giardiasis is metronidazole 250 mg tid for seven days, which also has activity against E. histolytica. Unfortunately, there are no reliable therapies for Cryptosporidiosis, though paromomycin or nitazoxanide may have activity and offer benefit. Supportive care with hydration and nutrition, as well as institution of an effective antiretroviral regimen, are crucial aspects of care since improvement in the immune system often helps eradicate the infection. In immunocompetent hosts, cryptosporidiosis is usually self-limited. It may be in this inmate's best interest to change his medications to a more potent antiretroviral regimen in an effort to improve his T-cell response and minimize his gastrointestinal side effects. If the regimen is not changed, the dose of Nelfinavir should be changed to 1,250 mg po bid as this dose is easier to take and is associated with fewer loose stools compared to the tid dose. There are no known drug-drug interactions between metronidazole, paromomycin, or nitazoxanide and the antiretrovirals he is currently taking. There is a drug-drug interaction between the oral solution form of the protease inhibitor amprenavir and metronidazole. This is not true for the capsule formulation of amprenavir.
Q: What infection-control measures should you recommend?
A: To minimize secondary transmission to others via fecal-oral spread, it is important to educate the inmate and staff on good hand-washing skills, particularly before and after meals and use of the restroom. He should be excluded from any kitchen work until his diarrhea has resolved and his stool is cleared of all organisms.
Bethany Weaver, D.O., M.P.H., is Acting Instructor of Medicine at the University of Washington Center for AIDS & STD Research (CFAR) and Northwest Correctional Medicine Education Program. Disclosures: Stockholder, Pfizer.