Stable phenotypic resistance of Candida species to amphotericin B conferred by preexposure to subinhibitory levels of azoles

Jose Antonio Vazquez, Maria T. Arganoza, Dina Boikov, Stephanie Yoon, Jack D. Sobel, Robert A. Akins

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The fungicidal activity of amphotericin B (AmB) was quantitated for several Candida species. Candida albicans and C. tropicalis were consistently susceptible to AmB, with less than 1% survivors after 6 h of exposure to AmB. C. parapsilosis and variants of C. lusitaniae and C. guilliermondii were the most resistant, demonstrating 50 to 90% survivors in this time period and as high as 1% survival after a 24-h exposure time. All Candida species were killed (<1% survivors) after 24 h of exposure to AmB. In contrast, overnight exposure to either fluconazole or itraconazole resulted in pronounced increases in resistance to subsequent exposures to AmB. Most dramatically, C. albicans was able to grow in AmB cultures after azole preexposure. Several other Candida species did not grow in AmB but showed little or no reduction in viability after up to 24 h in AmB. Depending on the growth conditions, Candida cells preexposed to azoles may retain AmB resistance for days after the azoles have been removed. If this in vitro antagonism applies to the clinical setting, treatment of patients with certain antifungal combinations may not be beneficial. The ability of some Candida isolates to survive transient exposures to AmB was not reflected in the in vitro susceptibility changes as measured by standard MIC assays. This finding should be considered in studies attempting to correlate patient outcome with in vitro susceptibilities of clinical fungal isolates. Patients who fail to respond to AmB may be infected with isolates that are classified as susceptible by standard in vitro assays but that may be resistant to transient antifungal exposures which may be more relevant in the clinical setting.

Original languageEnglish (US)
Pages (from-to)2690-2695
Number of pages6
JournalJournal of clinical microbiology
Volume36
Issue number9
StatePublished - Sep 1 1998
Externally publishedYes

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Azoles
Amphotericin B
Candida
Survivors
Candida albicans
Itraconazole
Fluconazole

ASJC Scopus subject areas

  • Microbiology (medical)

Cite this

Stable phenotypic resistance of Candida species to amphotericin B conferred by preexposure to subinhibitory levels of azoles. / Vazquez, Jose Antonio; Arganoza, Maria T.; Boikov, Dina; Yoon, Stephanie; Sobel, Jack D.; Akins, Robert A.

In: Journal of clinical microbiology, Vol. 36, No. 9, 01.09.1998, p. 2690-2695.

Research output: Contribution to journalArticle

Vazquez, Jose Antonio ; Arganoza, Maria T. ; Boikov, Dina ; Yoon, Stephanie ; Sobel, Jack D. ; Akins, Robert A. / Stable phenotypic resistance of Candida species to amphotericin B conferred by preexposure to subinhibitory levels of azoles. In: Journal of clinical microbiology. 1998 ; Vol. 36, No. 9. pp. 2690-2695.
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