Testing susceptibility of fungi to fluconazole

Scheven, M.

doi:10.1007/bf01964441

Cited by 4 publications

(11 citation statements)

References 4 publications

(2 reference statements)

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“…Earlier studies have indicated that disk diffusion might be used for the susceptibility testing of Candida isolates (2,3,23,26,(35)(36)(37)41). There are, however, problems with the reading of the results as pointed out by others, which we can verify.…”

Section: Discussionmentioning

confidence: 65%

“…Disk diffusion testing of Candida species to determine antibiotic susceptibility has been evaluated by several investigators and shown to have potential (2,3,12,23,35,36,41). We applied SRA for the calculation of interpretive zone diameter equivalents of MIC limits for the susceptibility categories and also for estimation of MICs for strains using the M-test (15,(17)(18)(19)(20).…”

Section: Methodsmentioning

confidence: 99%

“…All clinical isolates were tested by SRA once and the reference strains were tested four times. The fluconazole disk content for routine disk testing has tentatively been set to 25 g (2, 3,26,36,37). No disk recommendations are available for voriconazole testing.…”

Section: Methodsmentioning

confidence: 99%

“…This emergence of resistance to drugs has led to a growing demand for susceptibility testing of clinical yeast isolates (14,32,41,43). Comparisons between the standardized NCCLS broth macrodilution method (27) and microdilution methods (12,22,33,38), Etests (7,8,12,25,33,38), and disk diffusion methods (2,3,26,35,36,41) suggest a possibility of using the less expensive disk method in clinical microbiology laboratories. We have extended the analysis of azole disk diffusion tests by using singlestrain regression analysis (SRA) for studying azole regression lines among Candida species and for calibration of the disk test.…”

mentioning

confidence: 99%

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Fluconazole and Voriconazole Multidisk Testing of Candida Species for Disk Test Calibration and MIC Estimation

Kronvall

Karlsson

2001

J Clin Microbiol

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Fluconazole and voriconazole MICs were determined for 114 clinical Candida isolates, including isolates of Candida albicans, Candida glabrata, Candida krusei, Candida lusitaniae, Candida parapsilosis, and Candida tropicalis. All strains were susceptible to voriconazole, and most strains were also susceptible to fluconazole, with the exception of C. glabrata and C. krusei, the latter being fully fluconazole resistant. Single-strain regression analysis (SRA) was applied to 54 strains, including American Type Culture Collection reference strains. The regression lines obtained were markedly different for the different Candida species. Using an MIC limit of susceptibility to fluconazole of <8 g/ml, according to NCCLS standards, the zone breakpoint for susceptibility for the 25-g fluconazole disk was calculated to be >18 mm for C. albicans and >22 mm for C. glabrata and C. krusei. SRA results for voriconazole were used to estimate an optimal disk content according to rational criteria. A 5-g disk content of voriconazole gave measurable zones for a tentative resistance limit of 4 g/ml, whereas a 2.5-g disk gave zones at the same MIC level for only three of the species. A novel SRA modification, multidisk testing, was also applied to the two major species, C. albicans and C. glabrata, and the MIC estimates were compared with the true MICs for the isolates. There was a significant correlation between the two measurements. Our results show that disk diffusion methods might be useful for azole testing of Candida isolates. The method can be calibrated using SRA. Multidisk testing gives direct estimations of the MICs for the isolates.Infections with Candida species are common complications in immunocompromised patients and require adequate treatment, often with newer azole drugs. Particularly in AIDS patients with oropharyngeal and/or esophageal candidiasis there have been reports of increased azole resistance among Candida isolates (6,14,24,29,(32)(33)(34)44). This emergence of resistance to drugs has led to a growing demand for susceptibility testing of clinical yeast isolates (14,32,41,43). Comparisons between the standardized NCCLS broth macrodilution method (27) and microdilution methods (12,22,33,38), Etests (7,8,12,25,33,38), and disk diffusion methods (2,3,26,35,36,41) suggest a possibility of using the less expensive disk method in clinical microbiology laboratories. We have extended the analysis of azole disk diffusion tests by using singlestrain regression analysis (SRA) for studying azole regression lines among Candida species and for calibration of the disk test. Such a calibration method is required since no interpretive zone breakpoints are yet available. The SRA-derived multidisk test (M-test) was also used for MIC estimations of susceptibility to fluconazole and voriconazole, the two azole drugs included. Voriconazole is a new azole with more avid binding to the sterol 14␣-demethylase, thereby more effectively inhibiting ergosterol synthesis (22, 34). MATERIALS AND METHODSCandida isolates, species identifica...

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Section: Discussionmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Fluconazole and Voriconazole Multidisk Testing of Candida Species for Disk Test Calibration and MIC Estimation

Kronvall

Karlsson

2001

J Clin Microbiol

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“…There also remain doubts concerning the reliability of the NCCLS method for the detection of amphotericin B-resistant yeasts (30, 31). For these reasons susceptibility studies based on methods other than the reference standard continue to appear (5,7,8,22,29,33,34,36,37,39,40,42) and commercial susceptibility test systems such as the E test (9, 38), Alamar Blue (21, 23, 25), Autobac (29), ATBfungus (6, 28), and API (26) have been introduced and evaluated.Direct downscaling of the NCCLS reference method to a broth microdilution system is possible. The results of broth microdilution tests show fair to good agreement with those obtained by the original method (3,10,11,13,23,38), depending on the agent tested.…”

mentioning

confidence: 99%

Antifungal susceptibility testing of yeasts: evaluation of technical variables for test automation

Odds

Vranckx

Woestenborghs

1995

Antimicrob Agents Chemother

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The technical parameters for antifungal susceptibility testing with Candida species were reexamined to determine the optimal conditions for testing with semiautomated preparations of broth microdilution cultures, automated spectrophotometric readings of the cultures, and dose-response and endpoint determinations by means of a computer spreadsheet. Tests were based on proposed standard method M27P of the National Committee for Clinical Laboratory Standards for antifungal agents. RPMI 1640 broth with extra glucose to a final concentration of 2% gave higher and more reproducible drug-free control readings without affecting susceptibility endpoint readings. An inoculum of 8 ؋ 10 4 yeasts per ml prepared from a carbon-limiting broth culture without further standardization was found to give optimal control readings after 48 h of incubation at 37؇C. For flucytosine, fluconazole, itraconazole, and ketoconazole, endpoints based on 50% growth inhibition (50% inhibitory concentration) gave the minimum variation with inoculum size and the fewest endpoint differences with RPMI 1640 medium obtained from two different suppliers. The 50% inhibitory concentration was also the optimal endpoint for fluconazole and ketoconazole susceptibilities in comparison with broth macrodilution MICs determined by the method of the National Committee for Clinical Laboratory Standards. Intralaboratory reproducibility was determined by retrospective analysis of replicate results for isolates retested at random over a 2-year period. This approach showed less favorable reproducibility than has been reported from purpose-designed, prospective antifungal susceptibility studies, but it may better reflect real-life test reproducibility. Susceptibility data for 616 clinical isolates of yeasts, representing 16 Candida and Saccharomyces spp., confirmed the tendency of Candida lusitaniae isolates to show relatively low susceptibilities to amphotericin B, the tendency of Candida krusei isolates to show low flucytosine and fluconazole susceptibilities, and the presence of some isolates in the species Candida albicans, Candida glabrata, and Candida tropicalis with low susceptibilities to azole derivative antifungal agents. The study demonstrates the value of automation and standardization in all stages of yeast susceptibility testing, from plate preparation to data analysis.Interest in antifungal susceptibility testing has increased in recent years, as witnessed by the growing number of published articles in this field. Most investigations have focused on tests with fluconazole against pathogenic yeasts, particularly since reports have appeared suggesting that Candida isolates with reduced fluconazole susceptibilities are being encountered clinically after long-term fluconazole treatment (4,5,19,24,27,31,32,34,35,41). Current methods for antifungal susceptibility testing need to conform to three considerations, which overlap mutually. They should give results that correspond to the clinical outcome of antifungal treatment, that show some correlation to those ...

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Selection ofCandida glabrata strains with reduced susceptibility to azoles in four liver transplant patients with invasive candidiasis

Fortün

Román

Velasco

et al. 1997

Eur. J. Clin. Microbiol. Infect. Dis.

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The cases of four liver transplant recipients who developed invasive candidiasis (2 cholangitis, 1 perihepatic abscess, 1 candidemia) due to azole-resistant, Candida glabrata are reported. Three patients were receiving azolic compounds (2 itraconazole, 1 fluconazole) when the infection was diagnosed. All four patients received fluconazole as intestinal decontamination during the first three weeks post transplantation. The infections occurred two months after transplantation in all patients, and in one patient Candida infection was the direct cause of death. Infection of the biliary tree was the origin of candidiasis in three patients; the fourth patient developed neutropenic-related candidemia. Fluconazole MICs exceeded 16 micrograms/ml in all cases; itraconazole MICs were 16, 2, 1, and 2 micrograms/ml, respectively. The potential role of Candida species other than albicans in these patients after administration of azole agents is discussed.

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Testing susceptibility of fungi to fluconazole

Cited by 4 publications

References 4 publications

Fluconazole and Voriconazole Multidisk Testing of Candida Species for Disk Test Calibration and MIC Estimation

Fluconazole and Voriconazole Multidisk Testing of Candida Species for Disk Test Calibration and MIC Estimation

Antifungal susceptibility testing of yeasts: evaluation of technical variables for test automation

Selection ofCandida glabrata strains with reduced susceptibility to azoles in four liver transplant patients with invasive candidiasis

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