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Journal of Clinical Microbiology, April 2003, p. 1805-1808, Vol. 41, No. 4
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.4.1805-1808.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Mycetoma of the Foot Caused by Fusarium solani: Identification of the Etiologic Agent by DNA Sequencing
H. Yera,1 M. E. Bougnoux,2 C. Jeanrot,3 M. T. Baixench,1 G. De Pinieux,4 and J. Dupouy-Camet1*
Laboratoire de Parasitologie-Mycologie,1
Service d'Orthopédie,3
Service d'Anatomo-Cyto-Pathologie, Hôpital Cochin, 75014 Paris, France,4
Laboratoire de Microbiologie, Hôpital Ambroise-Paré, Boulogne-Billancourt, France2
Received 30 September 2002/
Returned for modification 27 November 2002/
Accepted 13 January 2003

ABSTRACT
We report a case of
Fusarium solani mycetoma of the foot that
could not be diagnosed by culture, but was correctly identified
after amplification and sequence analysis of fungal internal
transcribed spacers 1 and 2 and 5.8S ribosomal DNA regions.

CASE REPORT
A 51-year-oldmale truck driver from Mauritius, who had been
living in France since 1970, hurt his left foot with a handcart
in April 2000. The wound was swollen and excoriated and was
self-treated ineffectively with various local antiseptics for
several months. In September 2000, he presented to the Orthopedic
Department of Cochin University Hospital. Physical examination
showed tumefaction of the dorsal face of the left forefoot,
with a few nodules and fistulae (Fig.
1). A small fistula secreted
whitish pus. The patient had trouble walking and could not wear
shoes because of violent pain. X-ray films revealed a periosteal
reaction involving the second and third metatarsals, a heterogeneous
aspect of the first phalanx of the second toe, and involvement
of the second metatarso-phalangeal joint. Magnetic resonance
imaging confirmed the X-ray findings and also revealed massive
dorso-plantar infiltration of the forefoot. The wound was biopsied
by a dorsal approach. Direct examination of silver-stained imprints
of the biopsy specimen showed septate hyphae. Culture slowly
grew a beige filamentous fungus without spore formation. Identification
was unsuccessful. Histologically, the specimen consisted of
inflammatory tissue containing lymphocytes and altered polymorphonuclear
neutrophils; no hyphae were seen. In October, a second biopsy
done by a plantar approach was performed to confirm the fungal
infection. Direct examination and culture were again positive,
with a fungus of identical aspect, and careful microscopic examination
of the histological section showed two small fungal grains (Fig.
2). Precise identification was impossible, even after the use
of nutritionally deficient media (potato dextrose agar and malt
agar). Treatment was started with oral itraconazole (400 mg/kg
of body weight/day), and molecular identification of the fungus
was attempted.
The lesions failed to improve on itraconazole at 400 mg/day,
and serum drug levels were found to be inadequate. The patient
was hospitalized in late December 2000 with excruciating pain
of the left foot. The itraconazole dose was increased. Pain
diminished after a few days, and the patient was able to walk
after a few weeks. An itraconazole regimen of 600 mg/day was
pursued for 3 months, yielding the following levels in serum:
itraconazolemia, 275 µg/liter; hydroxy-itraconazolemia,
620 µg/liter. These values were close to usual therapeutic
levels (itraconazole, >250 µg/liter; hydroxy-itraconazole,
>1,000 µg/liter), but we preferred to increase the
daily dose to 800 mg for 4 months. Serum drug levels on this
regimen were not measured. Itraconazole was clinically and biologically
well tolerated, with normal liver enzyme activities and blood
cell counts. The itraconazole susceptibility of the isolate
could not be tested because of slow growth in vitro. However,
the itraconazole treatment was effective, so surgery was not
required. An X -ray film obtained in September 2001 was normal;
12 months after completion of treatment, the patient was pain
free and able to walk.
Mycetoma is a chronic pseudotumorous infection of the skin and subcutaneous tissue, occasionally including bone, caused by fungi (eumycetoma) or bacteria (actinomycetoma), generally inoculated traumatically. Mycetoma is usually localized to the foot and principally occurs in tropical and subtropical regions. We describe here a case of eumycetoma of the foot that was diagnosed by PCR and DNA sequencing.
Fungal DNA was extracted from culture material by the technique described by Hennequin et al. (11) with Chelex 100 resin (Bio-Rad Laboratories, Marne-la-Coquette, France) (21). The fungus-specific universal primers internal transcribed spacer 1 (ITS1) and ITS4 were used to amplify the internal transcribed spacer and 5.8S regions of fungal ribosomal genes (22). PCR amplification was performed in a reaction mixture (final volume, 50 µl) containing 50 mM KCl, 15 mM Tris-HCl (pH 8.0), 2.5 mM MgCl2, 200 µM each deoxynucleoside triphosphate, 0.4 µM each primer, 2.5 U of AmpliTaq Gold DNA polymerase (Applied Biosystems, Paris, France), and 10 µl of fungal DNA. Ten microliters of sterile water was tested as a negative control. DNA amplification was performed with the following temperature cycles: 95°C for 5 min; then 30 cycles of 20 s at 95°C, 60 s at 55°C, and 60 s at 72°C; and a final cycle at 72°C for 5 min. PCR products and a molecular weight maker were submitted to electrophoresis on 2.5% agarose gel containing ethidium bromide. A specific amplified fragment of 509 bp was obtained and purified and then was cycle sequenced in both directions with an automated sequencing system. A sequence of 509 bp was determined and compared to GenBank nucleotide sequences by using BLAST-N software (National Center for Biotechnology Information). Total identity was obtained with Fusarium solani (ITS1-5.8S rRNA-ITS2) sequences given under accession no. AF165874, AF150467, and AF440567. The molecular identification was repeated with each isolate obtained from the two biopsies and was carried out in two different laboratories.
About 23 cases of eumycetoma due to Fusarium species have been reported (Table 1). The patients' origins were the tropics (2-7, 10, 14, 16-20), Israel (15), and Italy (1) or were not specified (8, 9). Morphological identification of the Fusarium genus was often difficult, and species-level identification was only achieved in eight cases. Classically, identification is based on the white-yellowish color of the grains, the light-brown colonies (with a reddish diffusing pigment in some cases), and genus-characteristic sickle-shape spores (these can be absent). Five cases of mycetoma due to F. solani have previously been reported (5, 9, 17, 19, 20).
Advances in molecular technology using sequence areas within
the ribosomal DNA gene complex have shown promise for the rapid
and accurate identification of fungal pathogens (
12,
22). Particularly,
ribosomal DNA sequencing (
11) can readily identify
Fusarium species, as confirmed in the case of foot mycetoma described
here. These techniques are particularly welcomed when conventional
methods used in routine practice have failed and when fungal
pathogens cannot be cultivated. Development of molecular technology
could potentially impact care and improve clinical treatment
decisions.
Fusarium species are cosmopolitan fungi, which are thought to be inoculated into the skin by penetrative trauma. Our patient with a recent history of foot injury probably acquired the infection from the local French environment, because he had only spent 1 month (in 1996) in Mauritius since 1970. Interestingly, however, he had hurt the same foot 10 years previously while living in France, with a fracture of the first phalanx of the second toe. It is unlikely that the fungus was inoculated during his first injury, because he had no local clinical signs before the second injury. However, the first injury could have sensitized the tissues, allowing an easier development of the mycetoma.
Medical treatment of fungal mycetoma is usually disappointing. A case due to Fusarium has been treated with itraconazole (18), but extensive surgical excision could be necessary (3, 16). In our case, as noted above, high-dose oral itraconazole was effective without surgery, because the follow-up X-ray film obtained in September 2001 was normal (a magnetic resonance imaging control could not be performed because the patient was lost at follow up), and the patient was pain free and able to walk 12 months after completing treatment.

FOOTNOTES
* Corresponding author. Mailing address: Laboratoire de Parasitologie-Mycologie, Hôpital Cochin, 27 Rue du Fbrg Saint Jacques, 75014 Paris, France. Phone: 33 1 58 41 22 51. Fax: 33 1 58 41 22 45. E-mail:
jean.dupouy-camet{at}cch.ap-hop-paris.fr.


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Journal of Clinical Microbiology, April 2003, p. 1805-1808, Vol. 41, No. 4
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.4.1805-1808.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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