Intestinal microsporidiosis in a German patient with AIDS

Molecular techniques for detection, species differentiation, and phylogenetic analysis of microsporidia

Microsporidia are obligate intracellular protozoan parasites that infect a broad range of vertebrates and invertebrates. These parasites are now recognized as one of the most common pathogens in human immunodeficiency virus-infected patients. For most patients with infectious diseases, microbiological isolation and identification techniques offer the most rapid and specific determination of the etiologic agent. This is not a suitable procedure for microsporidia, which are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Although the diagnosis of microsporidiosis and identification of microsporidia by light microscopy have greatly improved during the last few years, species differentiation by these techniques is usually impossible and transmission electron microscopy may be necessary. Immunfluorescent-staining techniques have been developed for species differentiation of microsporidia, but the antibodies used in these procedures are available only at research laboratories at present. During the last 10 years, the detection of infectious disease agents has begun to include the use of nucleic acid-based technologies. Diagnosis of infection caused by parasitic organisms is the last field of clinical microbiology to incorporate these techniques and molecular techniques (e.g., PCR and hybridization assays) have recently been developed for the detection, species differentiation, and phylogenetic analysis of microsporidia. In this paper we review human microsporidial infections and describe and discuss these newly developed molecular techniques.

Intestinal microsporidiosis in patients with acquired immunodeficiency syndrome--report of three more German cases

Intestinal microsporidiosis with Enterocytozoon bieneusi was diagnosed in three of 18 HIV-infected patients with chronic diarrhoea. In two cases all known stages of the life cycle of E. bieneusi (merogonial plasmodia, sporogonial plasmodia, sporoblasts, spores) were found in duodenal biopsies by electron microscopical examination, whereas in the third case only merogonial and sporogonial stages were seen. Spores were also visible by light microscopy in semithin sections. Two patients were treated with albendazole (2 x 400 mg/day for 4 weeks) but showed no response. These findings underline the concept of the worldwide distribution of this parasite and verify that it is also frequent in Germany.

Human microsporidial infections

Microsporidia are obligate intracellular spore-forming protozoal parasites belonging to the phylum Microspora. Their host range is extensive, including most invertebrates and all classes of vertebrates. More than 100 microsporidial genera and almost 1,000 species have now been identified. Five genera (Enterocytozoon spp., Encephalitozoon spp., Septata spp., Pleistophora sp., and Nosema spp.) and unclassified microsporidia (referred to by the collective term Microsporidium) have been associated with human disease, which appears to manifest primarily in immunocompromised persons. The clinical manifestations of microsporidiosis are diverse and include intestinal, pulmonary, ocular, muscular, and renal disease. Among persons not infected with human immunodeficiency virus, ten cases of microsporidiosis have been documented. In human immunodeficiency virus-infected patients, on the other hand, over 400 cases of microsporidiosis have been identified, the majority attributed to Enterocytozoon bieneusi, an important cause of chronic diarrhea and wasting. Diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Initial detection of microsporidia by light microscopic examination of tissue sections and of more readily obtainable specimens such as stool, duodenal aspirates, urine, sputum, nasal discharge, bronchoalveolar lavage fluid, and conjunctival smears is now becoming routine practice. Definitive species identification is made by using the specific fluorescein-tagged antibody (immunofluorescence) technique or electron microscopy. Treatment options are limited, but symptomatic improvement of Enterocytozoon bieneusi infection may be achieved with the anthelmintic-antiprotozoal drug albendazole. Preliminary observations suggest that Septata intestinalis and Encephalitozoon infections may be cured with albendazole. Progress is being made with respect to in vitro propagation of microsporidia, which is crucial for developing antimicrosporidial drugs. Furthermore, molecular techniques are being developed for diagnostic purposes, taxonomic classification, and analysis of phylogenetic relationships of microsporidia.

Gastrointestinal symptoms in patients infected with human immunodeficiency virus: relevance of infective agents isolated from gastrointestinal tract

The correlation of gastrointestinal symptoms and infections in 186 consecutive patients with human immunodeficiency virus (HIV) infection undergoing diagnostic endoscopy (oesophagogastroduodenoscopy, n = 124; colonoscopy, n = 37; both, n = 25) was investigated. Biopsy and stool samples were examined for infective agents. Only weight loss (p = 0.003) and dysphagia (p = 0.027) were more common in patients at stage CDC IV compared with earlier stages. In three of 27 patients at stage II/III and in 93 of 159 patients at stage IV an infective agent was identified in stool or gastrointestinal biopsy specimen (p < 0.001). Cytomegalovirus (n = 35), Candida sp (n = 28), M avium complex (n = 10), and Cryptosporidium (eight) were the most frequent agents detected. At stage IV, diarrhoea was more frequent in infected compared with non-infected patients (p = 0.006); however, an infective agent was also found in 39 of 82 patients at stage IV without diarrhoea. The frequency of gastrointestinal symptoms was not consistently increased in patients harbouring specific infective agents compared with non-infected patients. Our findings indicate that the pathogenic relevance of a gastrointestinal infection in HIV infected patients has to be verified and indirectly support the existence of an HIV associated enteropathy.