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Journal of Clinical Microbiology, December 2004, p. 5954-5956, Vol. 42, No. 12
0095-1137/04/$08.00+0 DOI: 10.1128/JCM.42.12.5954-5956.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Usefulness of PCR Analysis for Diagnosis of Alveolar Echinococcosis with Unusual Localizations: Two Case Studies
Sophie Georges,1
Odile Villard,1
Denis Filisetti,1
Alexander Mathis,2
Luc Marcellin,3
Yves Hansmann,4 and
Ermanno Candolfi1*
Institut de Parasitologie et Pathologie Tropicale, Faculté de Médecine,1
Service d'Anatomie Pathologique Générale,3
Service de Maladies Infectieuses et Tropicales, Hôpitaux Universitaires de Strasbourg, Strasbourg, France,4
Institut für Parasitologie, Universität Zürich, Zurich, Switzerland2
Received 29 April 2004/
Returned for modification 16 June 2004/
Accepted 15 August 2004

ABSTRACT
The report presents two cases where diagnosis of alveolar echinococcosis
was confirmed by
Echinococcus multilocularis and
Echinococcus granulosus PCR. The extrahepatic osseous involvement and the
absence of initial hepatic involvement are unusual in both cases.
Due to limitations of serological interpretation, PCR was useful
to diagnose atypical echinococcosis.

CASE REPORTS
Case 1.
A 48-year-old man from a rural area in Lorraine, France, initially
presented with abdominal pain. Abdominal tomodensitometry detected
collection involving paravertebral and retroperitoneal areas
up to the kidneys. Surgical excision and drainage were required.
Three years later, skin fistulization had developed. Disease
progression led to destruction of bone in the 12th dorsal vertebra,
which was stable for many years. The diagnosis of Pott's disease
was suggested, although all tests for mycobacteria were negative.
After 17 years of evolution, the abdominal pain increased significantly.
Imaging techniques showed paravertebral collection with multiple
spinal thoracolumbar involvement, epidural infiltration with
intradural abscess, and hepatic calcifications. Diagnosis of
alveolar echinococcosis (AE) was made from the serum and fistula
specimens. Despite surgical treatment and parasitostatic medication,
the patient was admitted in a medical reanimation unit and died
rapidly from an encephalopathy of unknown origin associated
with a respiratory failure.
Case 2.
A 59-year-old woman, also from a rural area in Lorraine, France, presented with dorsal pain. Radiological investigations (tomodensitometry and magnetic resonance imaging) diagnosed a spondylitis localized at vertebrae D10 and D11. The disease developed rapidly to osseous destructions within a few months. Two surgical operations were needed for medullar decompression, and osteosynthesis was performed. Biopsy specimens from the 11th dorsal vertebra were processed for histological examination. Eosinophilic and hyaline membranes heavily stained by periodic acid-Schiff suggested a pellucid membrane of an AE. No scolices or hooklets were observed (data not shown). Once osseous AE was confirmed by PCR of the biopsy sample, a careful screening of the liver was performed. No abnormalities were found in imaging studies of the liver. The disease has progressed slowly, with aggravation of the vertebral lysis despite appropriate albendazole treatment. Table 1 compares clinical features and diagnostic analysis of these two cases of osseous AE.
Detection of Echinococcus-specific antibodies.
Detection of
Echinococcus-specific antibodies is routinely based
on the use of crude antigens and antigenic fractions (
22). An
in-house enzyme-linked immunosorbent assay (ELISA) with crude
Echinococcus granulosus hydatic cyst fluid antigen (HCF) obtained
from naturally infected sheep was performed as described previously
(
1). In addition, an Em2+ ELISA (Bordier Affinity Products,
Crissier, Switzerland), using a combination of the recombinant
antigen II/3-10 and the purified Em2 antigenic fraction of
Echinococcus multilocularis (
7), was performed in accordance with the manufacturer's
instructions.
Echinococcus immunoglobulin G (IgG) Western blotting
(LDBIO Diagnostics, Lyon, France) was performed as a confirmation
technique for the diagnosis of echinococcosis and was carried
out as reported previously (
12). In case 1, both HCF ELISA and
Em2+ ELISA detected a high titer of antibodies in serum. In
case 2, HCF ELISA was positive whereas Em2+ ELISA was negative.
The Western blotting detected
Echnicococcus-specific IgG in
sera of both patients. A distinct antigen recognition pattern
for each patient's serum is used to distinguish both species,
as shown in Fig.
1.
Detection of E. multilocularis and E. granulosus DNA by PCR.
DNA was extracted from drainage material and biopsy specimens
by binding to silica gel membranes (QIAamp DNA minikit; QIAGEN
SA, Courtaboeuf, France).
E. multilocularis DNA was detected
by a modified PCR described by Dinkel et al. (
6) and Stieger
et al. (
21) with the primer pair EM-H15 (5'-CCATATTACAACAATATTCCTATC-3')
and EM-H17 (5'-GTGAGTGATTCTTGTTAGGGGAAG-3'). A 200-bp product
from the
E. multilocularis 12S rRNA gene was amplified. PCR
amplification was performed within a 50-µl reaction volume
by using a hot-start
Taq DNA polymerase (HotStarTaq; QIAGEN
SA). The reaction mixture consisted of 10 µl of DNA template;
5 µl of 10
x HotStarTaq PCR buffer (including 1.5 mM [final
concentration] MgCl
2); 5 µl of dATP, dTTP, dGTP, and dCTP
(each at 200 µM [final concentration]); 1 µl of
each primer (1 µM [final concentration]); and 0.25 µl
of HotStarTaq DNA polymerase (1.25 U [final amount]). The thermal
cycling conditions were as follows: 95°C for 15 min; 40
cycles at 95°C for 30 s, 55°C for 30 s, and 72°C
for 30 s; and a final extension at 72°C for 5 min. Amplicons
were detected after electrophoresis on a 2% agarose gel by staining
the gel with ethidium bromide. Each sample was tested in duplicate.
In one assay, an internal control plasmid containing a size-modified
E. multilocularis target sequence was added to the reaction
mixture to detect the presence of PCR inhibitors in samples.
Failure to detect the corresponding 371-bp DNA band on gel electrophoresis
would indicate the presence of an amplification inhibitor in
the DNA template, and consequently the results in the corresponding
sample would be considered inconclusive.
E. granulosus.
DNA was detected by PCR amplification of a 255-bp product of the mitochondrial 12S rRNA gene, with the primers Eg1f (5'-CATTAATGTATTTTGTAAAGTTG-3') and Eg1r (5'-CACATCATCTTACAATAACACC-3'). The conditions of amplification reactions and the corresponding internal control target used were as previously described (20).
For patient 1, a test for E. multilocularis performed on material of fistula origin was positive (Fig. 2), whereas E. granulosus PCR was negative. For patient 2, a test for E. multilocularis carried out on biopsy specimens of vertebrae was positive (Fig. 2) whereas E. granulosus PCR was negative.
Discussion.
Although primary extrahepatic infection is well recognized in
cystic echinococcosis (CE), it is an extremely rare event in
AE. Indeed, only a few cases of AE without liver involvement
have been reported in the literature (
18). Bone manifestation
of AE or CE is rare. Osseous localization occurs in only 0.9
to 2.5% of infected CE patients (
2), and, to date, only 18 cases
of osseous AE have been reported (
3,
8,
14). In both cases reported
here, the presence of extrahepatic osseous involvement and the
absence of initial hepatic involvement are unusual. Differential
diagnosis includes tumors and infectious lesions, such as those
due to tuberculosis and bacterial abscess (
16). In case 1, the
patient had several treatments for tuberculosis over many years,
without microbiological evidence. The lack of improvement with
antibiotherapy finally led to new etiological research. However,
during the course of these years, AE had evolved and finally,
the patient died. This case illustrates the pejorative prognosis
of late diagnosis of AE. A fatal outcome may occur in more than
95% of untreated patients within a 10-year period following
diagnosis (
4).
Serological interpretation can be difficult in cases of extrahepatic manifestation and sometimes remains insufficient to differentiate AE from CE. HCF ELISA has relatively high sensitivity for echinococcosis: 91% for CE and 95% for AE (17). Nevertheless a lack of specificity and problems with the standardization of their use render interpretation difficult. Indeed, serological tests based on the use of total somatic antigens show a high degree of cross-reactivity with other parasites (17). By contrast, Em2+ ELISA using purified species-specific antigens has been used for immunodiagnosis of AE with encouraging results (7). The Em2+ ELISA has a high sensitivity of 97% in hepatic localization and a specificity of 74% with respect to cross-reactions due to infection with the closely related E. granulosus (7). In case 1, the positive Em2+ ELISA suggested an AE with cross-reaction, as indicated by a positive HCF ELISA. In contrast, Em2+ ELISA was negative in case 2, suggesting a CE. In both cases, Em2+ ELISA's results were confirmed by the Western blot pattern. Western blotting allowed the detection of serum IgG in 97% of Echinococcus-infected patients (12). It has a higher sensitivity than ELISA for the detection of echinococcosis and a specificity of 93%. However, it could differentiate E. multilocularis from E. granulosus in only 76% of cases (12).
PCR techniques have been developed to detect E. multilocularis and E. granulosus nucleic acids in biological samples (6, 9, 13, 19, 20). PCR is most frequently applied to drainage material and biopsy samples and is increasingly being accepted as a complementary diagnostic tool for echinococcosis (5, 10, 11, 14, 15). For patient 1, PCR confirmed the serological diagnosis, whereas for patient 2, PCR invalidated it. For patient 2, PCR and histological examination arrived at an accurate diagnosis of AE, whereas serological species identification failed.
Serological misdiagnosis may be due to low E. multilocularis-specific antibody titers and to unusual AE localization. Precise identification of the parasite species is crucial, especially in countries where both E. granulosus and E. multilocularis infections occur, as their management and prognosis are different. Our cases highlight the efficiency of PCR by contrast to the limitations of serological interpretation in the diagnosis of extrahepatic AE.

ACKNOWLEDGMENTS
We thank the Hôpitaux Universitaires de Strasbourg and
the Université Louis Pasteur de Strasbourg for their
financial support.

FOOTNOTES
* Corresponding author. Mailing address: Institut de Parasitologie et de Pathologie Tropicale, Faculté de Médecine, 3 rue Koeberlé, 67000 Strasbourg, France. Phone: 00 33 3 90 24 37 00. Fax: 00 33 3 90 24 36 93. E-mail:
ermanno.candolfi{at}medecine.u-strasbg.fr.


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Journal of Clinical Microbiology, December 2004, p. 5954-5956, Vol. 42, No. 12
0095-1137/04/$08.00+0 DOI: 10.1128/JCM.42.12.5954-5956.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
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