Quality control guidelines for National Committee for Clinical Laboratory Standards recommended broth macrodilution testing of amphotericin B, fluconazole, and flucytosine

The growth inhibition patterns of 764 clinical yeast isolates, in response to amphotericin B, flucytosine, itraconazole and fluconazole, were studied in order to determine the frequency of trailing growth and any impact this, as well as 24- or 48-h incubation periods, may have on minimum inhibitory concentration (MIC) results. A broth microdilution method following National Committee for Clinical Laboratory Standard No. M27A recommendations was used. Trailing growth was observed mainly with azoles. Furthermore, over 98% of isolates exhibiting a trailing effect at 24 h with fluconazole and itraconazole were either Candida albicans or Candida tropicalis. When comparing 24- and 48-h IC50 values, discrepancies were observed with itraconazole and fluconazole, respectively, in 18 and 11% of C. albicans and 24 and 30% of C. tropicalis. When comparing IC50 and IC80 values at 24 h, discrepancies were again essentially seen with itraconazole and fluconazole, respectively, in 11 and 10% of C. albicans, and 17 and 27% of C. tropicalis. In susceptibility tests performed with a microdilution method and read spectrophotometrically, 48-h IC80 values result in an unlikely high number of resistant isolates, indicating that a 24-h incubation and a 50% reduction in optical density may correlate better with clinical outcome.

Section: Interpretive Guidelinesmentioning

confidence: 80%

Impact of endpoint definition on the outcome of antifungal susceptibility tests with Candida species: 24- versus 48-h incubation and 50 versus 80% reduction in growth

St-Germain¹

2001

“…Paecilomyces variotii ATCC 22319 was included as the quality control strain and was run in conjunction with the case isolate in the susceptibility test. [5][6][7]…”

Section: In Vitro Susceptibility Testingmentioning

confidence: 99%

Central nervous system infection due to Penicillium chrysogenum

Kantarcıoğlu

Apaydın

Yücel

et al. 2004

Penicillium chrysogenum was isolated from three subsequent cerebrospinal fluid (CSF) specimens of a 73-year-old male patient without immunological compromise. The isolated was tested against five antifungal agents according to the NCCLS M38-P macrodilution method. MICs were determined as follows: amphotericin B (AMB), 2 microg ml(-1); fluconazole (FLZ), 8 microg ml(-1); itraconazole (ITZ), 1 microg ml(-1); flucytosine (5FC), 0.125 microg ml(-1); and terbinafine (TRB), 0.06 microg ml(-1). The patient has been cured with FLZ.

“…The P. variotii quality control strain ATCC 22319 with known MIC values, was run in conjunction with the test isolate in the susceptibility test. [12][13][14]…”

Section: Antifungal Susceptibility Testingmentioning

confidence: 99%

Paecilomyces variotii central nervous system infection in a patient with cancer

Kantarcıoğlu

Hatemi

Yücel

et al. 2003

Paecilomyces variotii was isolated from two subsequent cerebrospinal fluid (CSF) specimens of a cancer patient. Identification was confirmed through beta-tubulin and rDNA ITS sequencing. MICs were determined for seven antifungal agents; the isolate was found to be susceptible to amphotericin B (AMB), itraconazole (ITZ), ketaconazole (KTZ) and 5-fluorocytosine (5FC) but resistant to fluconazole (FLZ) and miconazole (MCZ). Despite antimycotic therapy, the infection proved to be fatal.