Workup of gastrointestinal microsporidiosis
C N Conteas1, E S Didier, O G Berlin
1Kaiser Permanente Medical Center, Los Angeles, Calif. 90027, USA.
Abstract:
Microsporidia, which are members of the phylum Microspora, are increasingly recognized as causing opportunistic infections in persons with immunodeficiency (e.g., AIDS). Diarrhea is the predominant clinical sign associated with infections by two Microsporidia, namely Enterocytozoon bieneusi and Encephalitozoon intestinalis (which was formerly named Septata intestinalis). Prevalence rates of microsporidiosis in persons with AIDS and chronic diarrhea range fron 7 to 50%. Transmission electron microscopy has been the gold standard by which to diagnose microsporidiosis and requires observing a polar filament which is the structure distinguishing Microsporidia from other organisms. Transmission electron microscopy is difficult, time-consuming, costly, relatively insensitive, and requires a great deal of expertise. As such, histochemical methods have been developed and improved for detecting Microsporidia. Diagnoses from stool specimens or enteric fluids can be made using the chitin-staining fluorochromes (e.g., Calcofluor White) and the modified trichrome stain which are highly sensitive, particularly when both are used. Immunofluorescent antibody staining methods are being developed to improve specificity, but reagents are not yet commercially available. Microsporidia can be detected most readily in tissue biopsies by Gram stain, Giemsa stain, or immunofluorescent antibody. Polymerase chain reaction methods are in their infancy for application, but should prove to be particularly sensitive and specific in the future.
Insights
Microsporidia cause opportunistic infections in immunocompromised individuals, often leading to diarrhea. New diagnostic methods like chitin-staining fluorochromes and modified trichrome stain offer improved detection of these microsporidia.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Parasitology
Background:
- Microsporidia are emerging opportunistic pathogens, particularly affecting individuals with immunodeficiency, such as those with AIDS.
- Microsporidiosis, commonly presenting as diarrhea, has prevalence rates of 7-50% in AIDS patients with chronic diarrhea.
- Enterocytozoon bieneusi and Encephalitozoon intestinalis are key microsporidia species causing human infections.
Purpose of the Study:
- To review diagnostic methods for microsporidiosis.
- To highlight the limitations of traditional diagnostic techniques.
- To discuss the advantages of newer histochemical and potential molecular diagnostic approaches.
Main Methods:
- Comparison of diagnostic techniques including Transmission Electron Microscopy (TEM), histochemical stains, and Polymerase Chain Reaction (PCR).
- Evaluation of chitin-staining fluorochromes (e.g., Calcofluor White) and modified trichrome stain for stool and enteric fluid analysis.
- Assessment of Gram stain, Giemsa stain, and immunofluorescent antibody staining for tissue biopsies.
Main Results:
- Transmission Electron Microscopy (TEM), while definitive, is labor-intensive, costly, and requires expertise.
- Chitin-staining fluorochromes and modified trichrome stain demonstrate high sensitivity for detecting microsporidia in stool and enteric fluids.
- Gram stain, Giemsa stain, and immunofluorescent antibody staining are effective for tissue biopsy diagnosis.
- PCR methods are still under development but show promise for high sensitivity and specificity.
Conclusions:
- Histochemical stains like Calcofluor White and modified trichrome stain offer sensitive and practical alternatives to TEM for diagnosing microsporidiosis.
- Immunofluorescent antibody staining and PCR represent promising future directions for improved diagnostic accuracy and specificity.
- Accurate diagnosis of microsporidiosis is crucial for managing opportunistic infections in immunocompromised patients.
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