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

Emerging pathogens: challenges and successes of molecular diagnostics

More than 50 emerging and reemerging pathogens have been identified during the last 40 years. Until 1992 when the Institute of Medicine issued a report that defined emerging infectious diseases, medicine had been complacent about such infectious diseases despite the alarm bells of infections with human immunodeficiency virus. Molecular tools have proven useful in discovering and characterizing emerging viruses and bacteria such as Sin Nombre virus (hantaviral pulmonary syndrome), hepatitis C virus, Bartonella henselae (cat scratch disease, bacillary angiomatosis), and Anaplasma phagocytophilum (human granulocytotropic anaplasmosis). The feasibility of applying molecular diagnostics to dangerous, fastidious, and uncultivated agents for which conventional tests do not yield timely diagnoses has achieved proof of concept for many agents, but widespread use of cost-effective, validated commercial assays has yet to occur. This review presents representative emerging viral respiratory infections, hemorrhagic fevers, and hepatitides, as well as bacterial and parasitic zoonotic, gastrointestinal, and pulmonary infections. Agent characteristics, epidemiology, clinical manifestations, and diagnostic methods are tabulated for another 22 emerging viruses and five emerging bacteria. The ongoing challenge to the field of molecular diagnostics is to apply contemporary knowledge to facilitate agent diagnosis as well as to further discoveries of novel pathogens.

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.

Microsporidia in duodenal biopsies from 72 HIV-infected patients with abdominal complaints

In order to evaluate the capacity of routine histological examination to detect microsporidiosis, a retrospective study was performed on 72 duodenal biopsies from 72 HIV-infected patients with upper abdominal symptoms of unknown cause. Two light microscopic cytological staining techniques, modified trichrome stain and the fluorochrome Calcofluor, were used. Two cases of microsporidiosis were detected among the 20 patients with prolonged diarrhoea of unknown origin in whom no etiological agent had been demonstrated by stool examination, mycobacterial and cytomegalovirus culture of biopsies, and histological routine staining of duodenal biopsies. The calculated confidence interval of 3-30% corresponds to the prevalence of intestinal microsporidiosis in HIV patients with prolonged diarrhoea in various parts of the world. The findings motivate attempts to identify microsporidia using special cytological staining methods. Improved methods of species identification are needed to aid in the choice of chemotherapy.

Effects of albendazole, fumagillin, and TNP-470 on microsporidial replication in vitro

Presently, the two most commonly used drugs for treating microsporidiosis in persons with AIDS are albendazole and fumagillin. Albendazole is effective for treating disseminated infections due to Encephalitozoon spp. but is variably effective against Enterocytozoon bieneusi infections. Fumagillin is highly effective when used topically to treat ocular infections with Encephalitozoon hellem or Encephalitozoon intestinalis but is too toxic for systemic use. In this study, the fumagillin analog TNP-470 was assayed for antimicrosporidial activity in vitro. The MICs of TNP-470 at which 50% of isolates were killed (MIC50s) were 0.35 +/- 0.21 and 0.38 +/- 0.11 ng/ml for E. intestinalis and Vittaforma corneae, respectively, and were similar to the MIC50s of fumagillin for these organisms, which were 0.515 +/- 0.002 and 0.81 +/- 0.014 ng/ml, respectively. The MIC50 of albendazole for E. intestinalis was 8.0 +/- 4.23 ng/ml, significantly less (P < 0.01) than its MIC50 for V. corneae, which was 55.0 +/- 7.07 ng/ml. TNP-470 inhibited replication of E. intestinalis in RK-13 cells if it was given at the same time as infection or if treatment was initiated 7 days later. In addition, treatment of the infected cultures with TNP-470 at a dose of 10 ng/ml for 2 weeks, followed by discontinuation of the drug treatment, resulted in no significant increase in E. intestinalis shedding during the following 3 weeks in culture. Because TNP-470 acts against both E. intestinalis and V. corneae, and because TNP-470 was found by others to be less toxic in vivo, TNP-470 may be a promising new drug for the treatment of microsporidiosis.

Tissue diagnosis of intestinal microsporidiosis using a fluorescent stain with Uvitex 2B

AIMS

To detect intestinal microsporidiosis in paraffin wax embedded biopsy specimens using a fluorescence technique incorporating optical brighteners.

METHODS

Eight HIV infected patients with confirmed intestinal microsporidiosis (six with Enterocytozoon bieneusi, one with Encephalitozoon intestinalis and one with Encephalitozoon cuniculi infection) and 10 without infection were studied. Tissue sections of paraffin wax embedded duodenal biopsy specimens were stained with 1% Uvitex 2B, coded and analysed independently by two investigators.

RESULTS

In all eight cases with confirmed intestinal microsporidian infection, spores could be detected easily in tissue sections using the fluorescence technique. Spores or other elements consistent with microsporidiosis were not found in the 10 patients without infection.

CONCLUSION

Staining of tissue sections from paraffin wax embedded intestinal biopsy specimens with stains incorporating Uvitex 2B is a rapid and easy technique for the diagnosis of intestinal microsporidiosis.

Detection of microsporidia (Enterocytozoon bieneusi) in intestinal biopsy specimens from human immunodeficiency virus-infected patients by PCR

Intestinal microsporidiosis has been implicated as a major cause of chronic diarrhea in human immunodeficiency virus (HIV)-infected patients. So far diagnosis depends on direct visualization of the parasites by light and transmission electron microscopy. We evaluated the diagnostic value of microsporidian DNA amplification by PCR on duodenal biopsy specimens obtained from patients with and without intestinal microsporidiosis caused by Enterocytozoon bieneusi. Thirteen HIV-infected patients (all CDC stage C3) were studied. Eight patients had intestinal microsporidiosis caused by E. bieneusi (n = 6), Septata intestinalis (n = 1), and Encephalitozoon cuniculi (n = 1); microsporidioses were diagnosed by light microscopy of stool samples and confirmed by light and electron microscopy of intestinal biopsy specimens. Five patients had no microsporidia in their stool samples or in their intestinal biopsy specimens, as examined by light and electron microscopy. Additionally, DNA prepared from Toxoplasma gondii derived from mouse ascites was used as a further control. A 353-bp DNA fragment of the small-subunit rRNA gene could be amplified from all six biopsy specimens infected with E. bieneusi, and the nature of the PCR products was confirmed by Southern blot hybridization. No amplification of DNA fragments was seen by using DNA extracted from biopsy specimens with S. intestinalis or E. cuniculi infection or without microsporidian infection and with template DNA extracted from T. gondii. The results suggest that PCR testing of intestinal biopsy specimens may be a useful approach to diagnosing microsporidiosis in HIV-infected patients.