Enterocytozoon bieneusi is clinically the most significant among the microsporidia causing chronic diarrhea, wasting, and cholangitis in individuals with human immunodeficiency virus/AIDS. Microscopy with either calcofluor or modified trichrome stains is the standard diagnostic test for microsporidiosis and does not allow species identification. Detection of E. bieneusi infection based on PCR is limited to a few reference laboratories, and thus it is not the standard diagnostic assay. We have recently reported the development and characterization of a panel of monoclonal antibodies against E. bieneusi, and in this publication we evaluated the specificity and sensitivity of an immunofluorescence assay (IFA), compared with PCR, in simian immunodeficiency virus-infected macaques. The IFA, which correlated with the primary PCR method, with a detection limit of 1.5 ؋10 5 spores per gram of feces, will simplify considerably the detection of E. bieneusi spores in clinical and environmental specimens and in laboratory and epidemiological investigations.Enterocytozoon bieneusi, an emerging enteric spore-forming protozoan, is clinically the most significant among the microsporidia which are linked to chronic diarrhea, wasting, and cholangitis in up to 30 to 50% of individuals with human immunodeficiency virus (HIV)/AIDS (2, 3, 25) as well as in recipients of organ transplants (17, 18) and malnourished children (23). E. bieneusi is occasionally symptomatic in healthy immunocompetent individuals (11,12,26) and also may contribute to traveler's diarrhea (10). E. bieneusi also infects other mammals, including simian immunodeficiency virus (SIV)-infected macaques, in which lesions, as in humans, are localized in the small intestine, gallbladder, and bile ducts (14).E. bieneusi infections are difficult to diagnose, primarily because the organisms are indistinguishable in size from bacteria and yeasts in stool. Until recently the diagnosis of intestinal microsporidiosis was based on the microscopic examination of feces stained with fluorochrome Uvitex 2B or by the modified trichrome or calcofluor white stain (6,7,13,24). These methods are nonspecific, as they stain chitin in the endospore layer of the spores, which is also present in some bacteria and yeasts. A more sensitive and specific assay is PCR, but it is not routinely used in clinical diagnosis (4,5,8,9,16,22).The recent derivation and characterization of specific monoclonal antibodies (MAbs) against E. bieneusi (21, 28) has made it possible to develop new and much simplified immune-based diagnostic assays. In this communication we have evaluated the sensitivity and specificity of an immunofluorescence assay (IFA) using MAbs against E. bieneusi for the detection of spores in fecal samples of SIV-infected macaques, compared with PCR.
MATERIALS AND METHODSFecal samples. Monthly fecal samples were obtained from a cohort of 12 SIV-infected rhesus macaques (Macaca mulatta), either experimentally or naturally infected with E. bieneusi, for 4 to 8 months to determine the patter...