Susceptibilities of Norwegian Candida albicans strains to fluconazole: emergence of resistance. The Norwegian Yeast Study Group

Abstract

All Candida albicans isolates in Norwegian microbiological laboratories in 1991 judged clinically important (except vaginal isolates) were collected. The isolates were tested for susceptibility to fluconazole with an agar dilution test and a commercially available agar diffusion test. A total of 212 strains (95%) were susceptible to fluconazole, and MICs for most of the strains (92%) were .1.56 pg/ml. The agar diffusion test using a 15-,Lg tablet and a 48-h incubation period separated resistant from susceptible strains with a wide margin. The only exception was a strain for which the MIC was 6.25 ILg/ml. The difference in zone size between the resistant and the susceptible populations of strains was 11 mm. Accordingly, it appears that the agar diffusion test is an appropriate method for detecting fluconazole resistance. The 12 fluconazole-resistant isolates originated from eight AIDS patients with oral or esophageal Candida infections. Seven of the patients had been given fluconazole for 1 month or more, often as self medication. Four had infections that were clinically resistant to fluconazole; one additional patient responded only when the dose was increased. All isolates recovered from these patients were analyzed by multilocus enzyme electrophoresis. The 12 C. albicans isolates belonged to five electrophoretic types, but three of four patients attending one hospital had isolates belonging to one electrophoretic type. One possible explanation for this finding could be that a nosocomial spread of resistant strains has occurred.

Comparison of Results Obtained by Testing with Three Different Agar Media and by the NCCLS M27-A Method for In Vitro Testing of Fluconazole against Candida spp

“…Twenty-six (86.6%) of the 30 MIC nonsusceptible strains were detected by the disk test on RPMIG and SHDM, and 27 (90%) were detected on MHGM. The agreement was lower when all three categories (susceptible, susceptible-dose dependent, and resistant) were used to analyze the data as has been observed by others (2,11,14,23).…”

“…The ability of distinguishing fluconazole-susceptible from -nonsusceptible Candida strains by agar diffusion has also been investigated by Sandven et al (22,23), Barry and Brown (2), Kirkpatrick et al (9), May et al (13), and Kronvall and Karlsson (10). In this study, of the 120 susceptible strains determined by microdilution, 116 (96.7%) were also susceptible by the diffusion test on MHGM, 115 (95.8%) were susceptible on RPMIG, and 113 (94.2%) were susceptible on SHDM.…”

Candidemia in Norway (1991 to 2003): Results from a Nationwide Study

“…The susceptibility method used has varied throughout this period. From 1991 until the end of 1993, a microdilution method in broth was used for amphotericin B and flucytosine and an agar dilution method for fluconazole (21). Since 1994, a colorimetric microdilution method based on Clinical and Laboratory Standards Institute (CLSI) recommendations has been used for the majority of the isolates (20).…”

The therapy of gastrointestinal infections associated with the acquired immunodeficiency syndrome

“…A number of studies of both oropharyngeal and oesophageal candidiasis have now documented clinical and microbiological resistance to these azole agents, most notably¯uconazole. 33,34 Testing of Candida isolates from patients with AIDS have found resistance in up to 33%.…”