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. 2018 Dec 4;6(4):123.
doi: 10.3390/microorganisms6040123.

Combination of Posaconazole and Amphotericin B in the Treatment of Candida glabrata Biofilms

Célia F Rodrigues  1   2 , Diana F Alves  3 , Mariana Henriques  4
Affiliations

Combination of Posaconazole and Amphotericin B in the Treatment of Candida glabrata Biofilms

Célia F Rodrigues et al. Microorganisms. .

Abstract

Candidemia cases have been increasing, especially among immunosuppressed patients. Candida glabrata is one of the most resistant Candida species, especially to the azole drugs, resulting in a high demand for therapeutic alternatives. The minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and minimum biofilm eradication concentration (MBEC) were determined for posaconazole (Pcz) and amphotericin B (AmB). The drug combinations of both drugs were evaluated on pre-formed biofilms of C. glabrata ATCC 2001, through XTT (2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay, colony forming units (CFU), crystal violet, and the fractional inhibitory concentration index (FICI). C. glabrata revealed higher susceptibility and biofilm reduction in the presence of AmB alone, but both drugs revealed a good capacity in the biomass elimination. In the majority of the tested combinations, the interactions were defined as indifferent (FICI ≤ 4). The combination of the two drugs does not seem to bring a clear advantage in the treatment of biofilms of C. glabrata.

Keywords: Candida; Candida glabrata; amphotericin B; antifungal combination; antifungal drug; biofilms; matrix; posaconazole; resistance.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Effect of posaconazole (A) and amphotericin B (B) on C. glabrata ATCC 2001 biofilms. Mean values of the logarithm of colony forming units are normalized by unit of area (Log10 CFU/cm2). Crystal Violet in a 48-hour-biofilm of C. glabrata ATCC 2001 are shown with and without posaconazole (C) (200; 300; 600 mg/L) and amphotericin B (D) (0.25; 0.5; 1 mg/L). The quantification of the biomass is presented by abs/cm2. (* p < 0.05; ** p < 0.001; *** p < 0.0005; **** p < 0.0001).
Figure 2
Figure 2
Checkerboard of the combinatory effect of different concentrations of Pcz and AmB. The values are related to the metabolic activity of the biofilms, determined through the XTT assay (A) (Bold: metabolic activity below 20%). Calculated FICI range of checkerboard experiments for C. glabrata ATCC 2001 (B).
Figure 3
Figure 3
Effect of the combination of posaconazole and amphotericin B (200 + 0.5 mg/L) on C. glabrata ATCC 2001 biofilms. Mean values of the logarithm of colony forming units normalized by unit of area (Log10 CFU/cm2) (A). Crystal Violet in a 48-hour-biofilm of C. glabrata ATCC 2001, with and without combination of posaconazole and amphotericin B (200 + 0.5 mg/L) (B). The quantification of the biomass is presented by abs/cm2. (**** p < 0.0001).
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