The triazole antifungal drugs terconazole and fluconazole are more effective than the imidazoles against yeasts causing vulvovaginal candidiasis. The triazoles generally require shorter drug regimens and are associated with lower rates of relapse and higher rates of cure. Given the wide spectrum of yeasts other than Candida albicans that are associated with vulvovaginitis, one or more species may be resistant to antifungal agents. With the widespread use of fluconazole, cases of resistant isolates of C. albicans and the appearance of infection by species of yeasts other than albicans have been reported. Cooper and McGinnis evaluated yeast isolates to determine in vitro susceptibility to terconazole and fluconazole.
Fifty clinical yeast isolates of C. albicans, Candida krusei, Candida parapsilosis, Candida tropicalis and Torulopsis glabrata were evaluated. A standardized broth macrodilution was used to determine the minimal inhibitory concentrations of terconazole and fluconazole.
For all species, the minimum inhibitory concentrations of terconazole were significantly lower than those of fluconazole. For each individual isolate, the minimum inhibitory concentration of terconazole was consistently lower than the corresponding concentration for fluconazole. Differences in the geometric mean of terconazole and fluconazole minimum inhibitory concentrations were most significant for C. krusei and T glabrata, followed by C. parapsilosis, C. tropicalis and C. albicans.
These observations strongly suggest that fluconazole is less fungistatic than terconazole. For each isolate assayed, the average zone of inhibition produced by terconazole was statistically greater in size than that produced by fluconazole. The extensive trailing end points exhibited by C. albicans and C. tropicalis in response to fluconazole, compared with the response to terconazole, suggest that a portion of the inoculum population is affected less by fluconazole than by terconazole.
The authors conclude that complete fungistasis appears to require significantly higher levels of fluconazole beyond the minimum inhibitory concentration for C. albicans and C. tropicalis. These data suggest that terconazole may be more effective than fluconazole in treating infections caused by different yeast species. Since in vitro results do not necessarily predict in vivo activity, it is possible that terconazole may be more effective than fluconazole in tr-eating vulvovaginal infections caused by yeast species other than C. albicans. -- BARBARA APGAR, M.D., M.S.
Cooper CR Jr, McGinnis MR. In vitro susceptibility of clinical yeast isolates to fluconazole and terconazole. Am j Obstet Gynecol 1996;175:1626-31.
COPYRIGHT 1997 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group
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