Among a large number of antifungal drugs, currently
available in this country are two imidazole derivatives,
bifonazole and lanconazole, and an allylamine derivative
terbinafine which play a major role in the topical treat-
ment of dermatophytosis and several other superficial
dermatophytoses. These three drugs, particularly the
latter two, have potent in vitro anti-dermatophytic activ-
ity (4, 10, 17) and share a common pharmacokinetic
property that they remain or accumulate within the horny
layer of the epidermis at substantially high levels after
topical application in animals and/or humans (6, 8, 12).
The mycological evaluation of therapeutic efficacy
of a given antifungal drug has usually been made by
culture studies using scales or other skin tissues from the
infected sites as specimens. However, when the above-
mentioned drugs or others with a similar biological fea-
ture were used for the treatment, the fungal recovery
could be appreciably affected by the specimen-associated
drug residues. If this is the case, the fungal recovery may
be underestimated, misleading us about the efficacy of the
A promising approach toward avoiding this problem
would be the use of a culture medium capable of can-
celing the putative carryover effect of the specimen-
associated antifungal drugs on the recovery culture. For
this purpose, we attempted to develop such a medium by
the supplementation of some appropriate deactivators
effective in counteracting imidazole and allylamine anti-
fungal drugs, including bifonazole, lanoconazole and
Microbiol. Immunol., 46(2), 83―88, 2002
Abbreviations: BAM, basal agar medium; BFZ, bifonazole;
CDSAM, combined deactivators-supplemented agar medium;
LCZ, lanoconazole; MIC, minimal inhibitory concentration;
SDA, Sabouraud’s dextrose agar; SDB, Sabouraud’s dextrose
broth; TBF, terbinafine.
*Address correspondence to Dr. Takuji Nakashima, Pharma-
ceutical R&D Laboratories, POLA Chemical Industries, Inc.,
560 Kasho-cho, Totsuka-ku, Yokohama, Kanagawa 244―0812,
Japan. Fax:＋81―45―826―7259. E-mail: email@example.com
Development of a New Medium Useful for the
Recovery of Dermatophytes from Clinical
Specimens by Minimizing the Carryover
Effect of Antifungal Agents
Takuji Nakashima*, 1, Akira Nozawa1, Takao Ito1, Toshiro Majima1, and Hideyo Yamaguchi2
1Pharmaceutical R&D Laboratories, POLA Chemical Industries, Inc., Yokohama, Kanagawa 244―0812, Japan, and 2Teikyo
University Institute of Medical Mycology, Teikyo University, Hachioji, Tokyo 192―0352, Japan
Received September 19, 2001. Accepted November 28, 2001
Abstract: Two surface-active compounds, egg lecithin and polysorbate 80, usually used as the deactivators
of various preservatives were tested whether they also counteract either or all of the three major topical anti-
fungal drugs, bifonazole (BFZ), lanoconazole (LCZ) and terbinafine (TBF). Both egg lecithin and polysor-
bate 80, when added to culture media up to final concentrations of 1.0 and 0.7%, respectively, antagonized
the anti-dermatophytic activity of the three drugs in a concentration-dependent manner. A greater extent
of antagonistic action was exerted when the two deactivators combined at their maximal levels tested were
added; MIC’s of BFZ were increased more than 30-fold and those of LCZ and TBF more than 200-fold com-
pared with the values obtained in the absence of the deactivators. Using the agar medium supplemented with
the combined deactivators, culture studies were carried out with skin tissues specimens taken from
guinea pigs whose feet were infected with dermatophytes and subsequently treated with 1% topical
preparations of the three antifungal drugs. The experimental data from this animal study demonstrated that
the combined deactivators-supplemented medium yielded increased numbers of fungi compared with the
basal medium. It looks, therefore, likely that the fungal recovery on the former medium more correctly
reflects to actual fungal burden in the infected lesions than the latter. All these results suggest that the com-
bined deactivators-supplemented medium is more useful for mycological evaluation of therapeutic effica-
cy of imidazole and allylamine drugs against dermatophytoses in both preclinical and clinical studies.
Key words: Medium, Deactivator, Antifungal agents, Tinea pedis
Chemother. 39: 314―319.
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