[Comparison of seven methods of in vitro susceptibility testing of clinical yeast isolates against fluconazole]

Antifungal susceptibility testing: practical aspects and current challenges

Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.

[Prerequisites for effective therapy of chronic recurrent vaginal candidiasis]

67 women with chronic recurrent or persistent vaginal candidosis between 5-79 years of age were seen in our outdoor department. In 34 cases, yeasts could be isolated in a vaginal swab taken at the first consultation. On average the patients reported 5 episodes per year during the last years. Typical symptoms consisted of pruritus vulvae, local inflammation and a curdy vaginal discharge. Nearly all of the women had received local or systemic antimycotic treatment for several times. In 53% (18 patients), C. albicans had been isolated, in 29% (10 patients) C. glabrata and in 9% (3 patients) C. krusei. While candidosis due to C. albicans and C. krusei was frequently associated with distressing complaints, infections with C. glabrata caused only very few symptoms. Independent of the species, severe and persistent infections were characterized by long term persisting specific IgM-antibody-titers and remarkable lack of IgG-antibodies. The laboratory parameters of WBC, CRP and immunelectrophoresis were normal. The minimum inhibitory concentrations (MIC) of 60 Candida strains against fluconacole were determined by microdilution assay. The MIC for C. albicans (n = 35) were between 0.78 and 3.125 micrograms/ml, for C. glabrata (n = 20) between 8 and 32 micrograms/ml and for C. krusei (n = 5) between 25 and 128 micrograms/ml. In 7 cases, local antimycotic treatment was sufficient. Correlating to the sensitivity, 18 women were treated with 100-800 mg fluconacole/d for 10-20 days. In 13 of them, clearance of symptoms and yeasts was achieved. The treatment of fluconacole-resistant strains with itraconazole (100-200 ml/d for 10-20 days) together with local application of nystatin (2 x 1 Mio. IE for 10 days) was without any effect. Three women with C. albicans, C. glabrata and C. krusei infection received a candidin-vaccination (0.005 BE/ml-500 BE/ml). In all of these cases, production of IgM-antibodies was induced. However, the clinical symptoms could not be influenced. Only in two cases it was not possible to reach a clearance of symptoms and yeasts. The results show the benefit of a precise differentiation before therapy. Serologic controls of antibody titers seem to be useful tools to control the efficacy of treatment.

[Fluconazole and itraconazole susceptibility testing with clinical yeast isolates and algae of the genus Prototheca by means of the Etest]

Preliminary own results suggest, that the Etest (produced by AB BIODISK, Solna, Sweden) performed on casitone medium meets the requirements of a routine test of yeast susceptibility to fluconazole and itraconazole. Testing of 46 clinical yeast isolates, of 5 strains of Exophiala dermatitidis and 4 strains of algae of the genus Prototheca revealed species-, genus- and strain-specific variations of the susceptibility to fluconazole and itraconazole. Candida glabrata was less susceptible to both triazoles than the other Candida species with exception of Candida krusei. Exophiala dermatitidis was highly susceptible to itraconazole. Prototheca wickerhamii and P. zopfii were resistant to both triazoles. Casitone medium is most appropriate for the determination of susceptibility to fluconazole and itraconazole by the Etest. The results of the Etest were comparable with those of a breakpoint test (microdilution method).

[Criteria for a microdilution susceptibility testing method of fluconazole: proposal of a standardized testing method for yeasts]

For the proposal of a standardised susceptibility testing method of yeasts against fluconazole the laboratory experiences of the last years and the results of a collaborative study of 21 laboratories from Germany and Austria were compiled. The present paper reflects the work flow and gives advice for performing the microdilution method.