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Journal of Clinical Microbiology, June 2001, p. 2371-2372, Vol. 39, No. 6
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.6.2371-2372.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
LETTERS TO THE EDITOR
Molecular Diagnosis of an Enterocytozoon bieneusi
Human Genotype C Infection in a Moderately Immunosuppressed Human
Immunodeficiency Virus- Seronegative Liver-Transplant Recipient with
Severe Chronic Diarrhea
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LETTER |
Microsporidia are intracellular parasites affecting the whole
animal kingdom (11). The species most often encountered in humans is Enterocytozoon bieneusi. Intestinal E. bieneusi infections have been reported in several hundred human
immunodeficiency virus (HIV) patients, while E. bieneusi
infections in HIV-negative patients are extremely rare
(11). We report what is to our knowledge the first finding
of an intestinal infection caused by E. bieneusi human
genotype C (based on analysis of the ribosomal DNA [rDNA] internal
transcribed spacer [ITS] sequence) diagnosed by PCR in a
liver-transplant recipient.
A 36-year-old HIV-negative woman receiving tacrolimus as a single
immunosuppressive treatment after liver transplantation 5 years ago
developed watery, unbloody diarrhea. Seven months after the onset of
her symptoms, she was admitted for evaluation of chronic diarrhea, with
20 to 25 bowel movements per day. Several stool samples were negative
for bacterial, viral, and parasitic pathogens. Two stool smears stained
by the modified trichrome technique (Weber's chromotrope-based stain)
(12) yielded abundant microsporidian spores. Fresh stool
samples were analyzed by PCR, which allowed for the identification of
the microsporidian species as E. bieneusi (5).
PCR findings were verified by DNA sequencing of the amplified gene
products. Upon albendazole therapy (800 mg/day) for 6 weeks, the
frequency of bowel movements diminished dramatically to 2 to 3 per day,
while stool samples obtained after 2 and 4 weeks showed no reduction in
microsporidial spores and remained PCR positive.
E. bieneusi infections are extremely rare in HIV-negative
patients, affecting mainly otherwise immunocompromised patients (11). Only five cases of human intestinal E. bieneusi infection in solid organ recipients have been reported
(Table 1). In all cases, diarrhea started
more than 18 months after transplantation, indicating that intestinal
E. bieneusi infection might be expected only after a
prolonged period of immunosuppression. The extent of immunosuppression,
however, may not be severe, since our patient developed intestinal
microsporidiosis despite a moderate immunosuppressive therapy of
tacrolimus without cortisone. Moreover, the number of CD4-positive
T-helper cells per microliter was above 200 in all solid organ
recipients with intestinal microsporidiosis.
Currently, no curative therapy for E. bieneusi infection
exists. Albendazole, which is effective against microsporidia other than E. bieneusi, seems to alleviate diarrhea in E. bieneusi-infected patients without clearing the infection
(11). In the three successfully treated transplant
patients with E. bieneusi infection, the discontinuation of
the immunosuppressive therapy was probably what improved the patients'
health conditions (3, 6).
The diagnosis of infections caused by E. bieneusi has been
markedly improved by the use of Weber's chromotrope-based stain (12). However, there are still problems in finding
microsporidial spores in human feces using both light microscopy
and PCR (9). For species identification, both transmission
electron microscopy and PCR are considered "gold standards"
(11). In solid organ recipients E. bieneusi was
identified by at least one of the gold standard methods mentioned above
in three patients who were recipients for kidney transplants and in
another one who received a heart-lung transplant. PCR was used only for
the three kidney recipients and for our liver-transplant patient.
The detection of E. bieneusi spores in pig fecal samples
(2) raised the question of whether or not animals may
serve as reservoirs for this microsporidian species. Breitenmoser et
al. (1) demonstrated that E. bieneusi genotypes
from animal origins were different from those originated from humans by
comparing rDNA ITS sequences. To date, four different human-derived
E. bieneusi genotypes, named A, B, C, and D, are known
(1, 10). In our patient the underlying E. bieneusi strain was identified as genotype C, which has been found
previously only in HIV-positive patients (1, 10).
In conclusion, we report the first case of an E. bieneusi
human genotype C infection in a liver-transplant patient diagnosed by
molecular methods. Intestinal E. bieneusi infection might
become a medical problem in solid organ transplant recipients,
especially after a long time of immunosuppressive therapy. The degree
of immunosuppression, however, does not seem to have to be as severe as
for HIV patients to cause disease. The discontinuation of
immunosuppressive therapy might be one option to achieve a medical
cure, while albendazole may lead to the alleviation of symptoms without
eradicating the pathogen.
| |
ACKNOWLEDGMENTS |
We thank Rainer Weber for critically reading the manuscript. We are
grateful to Rainer Weber and Peter Deplazes for continuous support in
the diagnosis of microsporidial infections.
| |
FOOTNOTES |
*
Phone: 49-89-5160-5200
Fax: 49-89-5160-5202
E-mail: heesemann{at}m3401.mpk.med.uni-muenchen.de
| |
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| | | | |
Andreas Sing
Karin Tybus
Jürgen Heesemann*
Max von Pettenkofer-Institut für Hygiene und Medizinische
Mikrobiologie
Ludwig-Maximilians-Universität
80336 Munich, Germany
|
| | | | |
Alexander Mathis
Institut für Parasitologie
Universität Zürich
8057 Zürich, Switzerland
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Journal of Clinical Microbiology, June 2001, p. 2371-2372, Vol. 39, No. 6
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.6.2371-2372.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
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