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Journal of Clinical Microbiology, February 2003, p. 911, Vol. 41, No. 2
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.2.911.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Multidrug-Resistant Trichosporon asahii Isolates Are Susceptible to Voriconazole

LETTER
We recently described the recovery of six clinical isolates
of
Trichosporon asahii from nongranulocytopenic patients that
exhibited reduced susceptibilities to amphotericin B, flucytosine,
ketoconazole, itraconazole, and fluconazole (
7). In a recent
paper Paphitou et al. reported (
6) that the new investigational
triazoles including voriconazole were highly potent against
24 isolates of
Trichosporon asahii (MIC and minimal fungicidal
concentration [MFC] of 0.25 and 0.5 mg/liter, respectively),
confirming the prior observation that voriconazole has a lower
MIC for
T. asahii than do other azoles (
4).
Recently, the NCCLS has recommended testing yeasts for susceptibility to new triazoles including voriconazole (M27-A2) (5), and a commercial Etest kit for voriconazole has become available. Consequently, we performed susceptibility testing for our T. asahii multidrug-resistant isolates against voriconazole (7). The results (Table 1) strongly indicate that these six isolates, which exhibit reduced susceptibilities to fluconazole, are highly susceptible to voriconazole. The MICs and MFCs of voriconazole for these isolates are close (0.125 to 0.25 and 0.25 to 1.0 mg/liter, respectively), suggesting fungicidal activity of voriconazole.
Voriconazole is an expanded-spectrum synthetic triazole derivative
of fluconazole. It inhibits the enzyme lanosterol 14-

-demethylase
of
Candida albicans and
Aspergillus fumigatus with potencies
1.6 and 160 times greater, respectively, than those of fluconazole
(
3). Its potent fungicidal activity is likely due to the high
affinity of voriconazole for fungal 14-

-demethylase, a concept
supported by ultrastructural and biochemical analysis (
1). However,
unlike fluconazole, voriconazole also inhibits 24-methylene
dihydrolanosterol demethylation of certain yeasts and filamentous
fungi (
3). These two reasons may explain why voriconazole may
be effective in the treatment of mycoses like trichosporonosis
that do not respond to other azoles. According to a new study,
voriconazole is "superior" to amphotericin B for treating life-threatening
invasive aspergillosis (
2) and was recently approved in some
European countries for the treatment of invasive aspergillosis.
In our previous paper (7) we emphasized the importance of the patient's basic immune status in determining the outcome of T. asahii infection. We concluded that in vitro resistance to antifungal drugs might not be critical in immunocompetent patients. However, immunocompromised patients may be dependent on fungicidal drug activity, so that infection with multidrug-resistant T. asahii isolates may be fatal in this population. Our new data with the low MICs and MFCs of voriconazole that confirm other in vitro studies suggest that voriconazole may offer a clinical solution in trichosporonosis when other antifungal drugs fail.

REFERENCES
1 - Ghannoum, M. A., and D. M. Kuhn. 2002. Voriconazolebetter chances for patients with invasive mycoses. Eur. J. Med. Res. 7:242-256.[Medline]
2 - Herbrecht, R., D. W. Denning, T. F. Patterson, J. E. Bennett, R. E. Greene, J. W. Oestmann, W. V. Kern, K. A. Marr, P. Ribaud, O. Lortholary, R. Sylvester, R. H. Rubin, J. R. Wingard, P. Stark, C. Durand, D. Caillot, E. Thiel, P. H. Chandrasekar, M. R. Hodges, H. T. Schlamm, P. F. Troke, and B. de Pauw. 2002. Voriconazole versus amphotericin B for primary therapy of invasive aspergillosis. N. Engl. J. Med. 347:408-415.[Abstract/Free Full Text]
3 - Masia Canuto, M., and F. Gutierrez Rodero. 2002. Antifungal drug resistance to azoles and polyenes. Lancet Infect. Dis. 2:550-563.[CrossRef][Medline]
4 - McGinnis, M. R., L. Pasarell, D. A. Sutton, A. W. Fothergill, C. R. Cooper, Jr., and M. G. Rinaldi. 1998. In vitro activity of voriconazole against selected fungi. Med. Mycol. 36:239-242.[CrossRef][Medline]
5 - National Committee for Clinical Laboratory Standards. 2002. Reference method for broth dilution antifungal susceptibility testing of yeasts, approved standard, 2nd ed. M27-A2, vol. 22. National Committee for Clinical Laboratory Standards, Wayne, Pa.
6 - Paphitou, N. I., L. Ostrosky-Zeichner, V. L. Paetznick, J. R. Rodriguez, E. Chen, and J. H. Rex. 2002. In vitro antifungal susceptibilities of Trichosporon species. Antimicrob. Agents Chemother. 46:1144-1146.[Abstract/Free Full Text]
7 - Wolf, D. G., R. Falk, M. Hacham, B. Theelen, T. Boekhout, G. Scorzetti, M. Shapiro, C. Block, I. F. Salkin, and I. Polacheck. 2001. Multidrug-resistant Trichosporon asahii infection of nongranulocytopenic patients in three intensive care units. J. Clin. Microbiol. 39:4420-4425.[Abstract/Free Full Text]
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Rama Falk Dana G. Wolf Mervyn Shapiro Itzhack Polacheck*
Department of Clinical Microbiology and Infectious Diseases The Hebrew University-Hadassah Medical Center P.O. Box 12000 Jerusalem 91120, Israel
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* Phone: 972-2-677-6592, Fax: 972-2-641-9545, E-mail: Itzhack.Polacheck{at}huji.ac.il |
Journal of Clinical Microbiology, February 2003, p. 911, Vol. 41, No. 2
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.2.911.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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