Coinfection with Giardia lamblia and Enterocytozoon bieneusi in a patient with acquired immunodeficiency syndrome and chronic diarrhea.

Diarrhea is an important clinical problem in immunosuppressed patients with acquired immunodeficiency syndrome (AIDS). There are numerous classical as well as emerging enteric pathogens that can produce diarrhea; however, these agents can be missed when only one method, such as microbiological examination of stool, is used for diagnosis. The endoscopic biopsy is a sensitive method for diagnosis of many viral, fungal, and parasitic infections of the gastrointestinal tract. Although only one agent is often identified in mucosal biopsies from these immunosuppressed patients, coinfection with multiple microbial agents is being increasingly recognized. Giardia infection is not as prevalent as other pathogens in patients with AIDS, but it remains an important diarrheal agent that is potentially curable. However, there have been only rare reports of coinfections with giardiasis and other infectious agents. This report describes a patient with AIDS and chronic diarrhea who had repeated negative stool examinations for ova and parasites. Light and electron microscopic examination of subsequent endoscopically obtained small intestinal biopsies revealed coinfection with two parasites, Enterocytozoon bieneusi and Giardia lamblia. Following treatment with metronidazole for giardiasis, the diarrhea persisted, but was less severe. This report also describes the diagnostic features of Giardia and Enterocytozoon infections in biopsy tissues and emphasizes the importance of identifying enteric coinfections in patients with AIDS to ensure timely and specific modes of therapy.