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Infections with other intestinal protozoa, such as Entamoeba histolytica and Blastocystis
hominis have also occurred in patients with AIDS, but not to a significant degree. They may
cause diarrhea, often mild and similar to that seen in immunocompetent hosts, but they are
usually enteric commensals.[487,662,676] Visceral leishmaniasis, caused by L donovani, may
affect the gastrointestinal tract, and the amastigotes may be seen in macrophages scattered in the
lamina propria with hematoxylin-eosin or Giemsa stains.[515]
Coccidian infections are common in animals such as dogs, producing the disease known
as sarcocystis, which is predominantly a gastrointestinal infection, though dissemination to other
internal organs or to muscle is possible. Diarrheal illness from sarcocystis has been reported
with AIDS. Intestinal biopsies may demonstrate the microgametocyte and macrogametocyte
stages of sarcocystis in the lamina propria, and the schizont stage may be seen in liver, by light
microscopy. Sporulated oocysts may be found in stool.[677]

BACTERIAL ENTERIC INFECTIONS.-- Besides the usual opportunistic infections,
bacterial infections can occur in association with HIV infection. Enteric bacterial pathogens may
produce more severe, recurrent, or persistent disease in HIV-infected persons, or be more likely
to produce extraintestinal disease. Enteric bacterial infections usually produce stools that do not
contain occult blood or leukocytes. Definitive diagnosis is made by stool culture.[499,678]
Salmonella species (not typhi) can occur in persons at risk for HIV infection, but most
often after clinical AIDS is apparent. Gastrointestinal Salmonella infections have a propensity to
result in septicemia and to relapse, particularly when CD4 lymphocyte counts are low. Recurrent
Salmonella infection is a criterion for diagnosis of AIDS in adults and children, and when
suspected blood culture should be performed.[391,392] Fever is common. Recurrence or failure
to respond to antibiotic therapy may occur, though amoxicillin, trimethoprim-sulfamethoxazole,
or ciprofloxacin appear to be appropriate therapeutic choices for Salmonella or Shigella
infections. Patients taking zidovudine have a lower risk for development of salmonellosis.
Typhoid fever has been infrequently reported in male homosexuals and in association with
AIDS.[499,662,678]
Campylobacter jejuni infections often appear after development of clinical AIDS and are
more frequent and severe than in patients without AIDS. Campylobacter jejuni infections are
best treated with either erythromycin or ciprofloxacin.[662] Enteropathogenic E. coli are seen
with HIV infection, most often in association with persistent diarrhea in children of developing
nations.[499,662,678] Helicobacter pylori infection can appear in HIV-infected persons with
chronic gastritis, with a similar histologic appearance of inflammation, erosions, or ulcers, but
with a lower incidence than that for non-HIV-infected persons.[679] HIV-infected patients with
H. pylori have a higher mean CD4 count than persons infected with HIV who do not have H.
pylori. The gastritis associated with H. pylori is more severe in persons with HIV infection.[680]
Occasionally, a low-grade small intestinal bacterial overgrowth of mostly aerobic bacteria may
lead to malabsorption and diarrhea.[662]
Shigella infections tend to occur early with HIV infection, and half may be accompanied
by a bacteremia. For men having sex with men, shigellosis is predominantly a sexually
transmitted disease, with the greatest risk from direct oral-anal contact and HIV infection
contributing to increased host susceptibility.[681] Campylobacter jejuni can produce a
proctocolitis, and patients often do not have fever. Clostridium difficile infection may occur in
AIDS patients treated with broad-spectrum antibiotics, may produce pseudomembranous colitis,
and may not respond promptly to therapy. Vibrio parahaemolyticus, which can lead to colitis