Abstract
We examined the effects of temperature and inoculum on the agreement of macro- and microdilution broth MICs of five antifungal agents against six isolates of Candida species or Torulopsis glabrata. Incubation temperature affected results with amphotericin B, flucytosine, fluconazole, and SCH 39304, producing better agreement at 35 degrees C than at 37 degrees C. Agreement between methods was better with an inoculum size of 10(2) than with one of 10(4) yeast cells per ml in testing fluconazole or SCH 39304, and the discrepancies seen with a higher incubation temperature and a larger inoculum appeared to be additive. However, inoculum size did not seem to affect agreement between methods in testing amphotericin B, flucytosine, or ketoconazole. Regardless of test conditions, macrodilution broth MICs of amphotericin B for different isolates were strikingly higher than microdilution test MICs, with mean differences being greater than ninefold under some test conditions. We conclude that for most currently available antifungal agents, an incubation temperature of 35 degrees C and a starting yeast inoculum of less than 10(4) cells per ml improve the agreement between macro- and microdilution broth tests.
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- Barry A. L., Jones R. N., Gavan T. L. Evaluation of the micro-media system for quantitative antimicrobial drug susceptibility testing: a collaborative study. Antimicrob Agents Chemother. 1978 Jan;13(1):61–69. doi: 10.1128/aac.13.1.61. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Calhoun D. L., Galgiani J. N. Analysis of pH and buffer effects on flucytosine activity in broth dilution susceptibility testing of Candida albicans in two synthetic media. Antimicrob Agents Chemother. 1984 Sep;26(3):364–367. doi: 10.1128/aac.26.3.364. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Calhoun D. L., Roberts G. D., Galgiani J. N., Bennett J. E., Feingold D. S., Jorgensen J., Kobayashi G. S., Shadomy S. Results of a survey of antifungal susceptibility tests in the United States and interlaboratory comparison of broth dilution testing of flucytosine and amphotericin B. J Clin Microbiol. 1986 Feb;23(2):298–301. doi: 10.1128/jcm.23.2.298-301.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Galgiani J. N. Antifungal susceptibility tests. Antimicrob Agents Chemother. 1987 Dec;31(12):1867–1870. doi: 10.1128/aac.31.12.1867. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Galgiani J. N., Reiser J., Brass C., Espinel-Ingroff A., Gordon M. A., Kerkering T. M. Comparison of relative susceptibilities of Candida species to three antifungal agents as determined by unstandardized methods. Antimicrob Agents Chemother. 1987 Sep;31(9):1343–1347. doi: 10.1128/aac.31.9.1343. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jordan G. W., Hoeprich P. D. Susceptibility of three groups of Staphylococcus aureus to newer antimicrobial agents. Antimicrob Agents Chemother. 1977 Jan;11(1):7–12. doi: 10.1128/aac.11.1.7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MacKerrow S. D., Merry J. M., Hoeprich P. D. Effect of buffers on testing of Candida species susceptibility to flucytosine. J Clin Microbiol. 1987 May;25(5):885–888. doi: 10.1128/jcm.25.5.885-888.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McIntyre K. A., Galgiani J. N. In vitro susceptibilities of yeasts to a new antifungal triazole, SCH 39304: effects of test conditions and relation to in vivo efficacy. Antimicrob Agents Chemother. 1989 Jul;33(7):1095–1100. doi: 10.1128/aac.33.7.1095. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McIntyre K. A., Galgiani J. N. pH and other effects on the antifungal activity of cilofungin (LY121019). Antimicrob Agents Chemother. 1989 May;33(5):731–735. doi: 10.1128/aac.33.5.731. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pfaller M. A., Burmeister L., Bartlett M. S., Rinaldi M. G. Multicenter evaluation of four methods of yeast inoculum preparation. J Clin Microbiol. 1988 Aug;26(8):1437–1441. doi: 10.1128/jcm.26.8.1437-1441.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]