M E Lynch

Comparative in vitro activity of antimycotic agents against pathogenic vaginal yeast isolates

Although numerous antimycotic agents are available for the treatment of yeast vaginitis there is little comparative data on the in vitro activity of these drugs. In the present two-part study, in vitro macro-broth dilution sensitivity tests were performed on a total of 377 clinical vaginal yeast isolates of nine different species. Antimycotics surveyed included amphotericin B, 5-fluorocytosine and eight azole derivatives. Results show that all vaginal Candida albicans isolates were uniformly sensitive at low concentration to all 10 antimycotics tested. However, non-albicans species, especially Candida glabrata and Saccharomyces cerevisiae, manifested several-fold increases in minimal inhibitory concentrations to all azoles tested except butoconazole. In particular, the in vitro potency of fluconazole and terconazole against species other than C. albicans was relatively poor, whereas the drugs demonstrating the best activity were itraconazole, butoconazole and saperconazole. Susceptibility testing of vaginal C. albicans isolates is not routinely indicated, even in patients with recurrent vaginitis and should be reserved for selected organisms, especially non-albicans species, in patients with clinical failure only.

Role of antifungal drug resistance in the pathogenesis of recurrent vulvovaginal candidiasis

The aetiology of recurrent vulvovaginal candidiasis (RVVC) caused by Candida albicans remains unclear. To adequately address the role of antifungal resistance as a potential mechanism for RVVC, a longitudinal susceptibility analysis of 177 C. albicans isolates collected from 50 C. albicans RVVC patients over a period of 3 months to 7 years was performed. Antifungals tested included clotrimazole, ketoconazole, miconazole, itraconazole and fluconazole. Results showed that all vaginal isolates were uniformly susceptible to all drugs tested and that successive isolates from individual patients did not show increased resistance to any drug despite long-term exposure to azoles. These results suggest that episodes of RVVC caused by C. albicans are rarely of ever attributable to azole antifungal resistance.

Flow cytometric analysis of germ tube formation in Candida albicans

The transition from the blastospore to the hyphal phase in Candida albicans is an important step in the pathogenesis of candidiasis. We present the application of flow cytometry (FCM) to the analysis of germ tube (GT) formation in large numbers of yeast cells. FCM parameters of 90° vs. forward angle light scatter, GT-specific fibrinogen (Fbn) binding fluorescence, and relative DNA content were used to provide a means of monitoring GT formation over time. FCM measurements of 90° vs. forward angle light scatter distinguished blastospores from GTs, whereas detection of Fbn binding to GTs by indirect immunofluorescence was used to quantitate GT formation. Under conditions favoring germination, a five-fold average increase in Fbn binding was observed over a 120 min period in clinical and type culture strains of C. albicans, but not in a GT-deficient mutant of C. albicans. Cell sorting was used to confirm that Fbn binding correlated with percent GT formation and increased GT length. DNA analysis by FCM showed i...