Antibiofilm activity of manogepix, ibrexafungerp, amphotericin B, rezafungin, and caspofungin against Candida spp. biofilms of reference and clinical strains

Abstract

This study comprehensively assessed the activity of manogepix (MNGX), ibrexafungerp (IBF), amphotericin B (AMB), rezafungin (RZF), and caspofungin (CAS) against planktonic cells and mature biofilms of Candida spp.-reference and clinical strains using the Calgary biofilm device. Mature-phase biofilms of C. albicans, C. auris (clades I, II, III, IV), and C. parapsilosis were exposed to a range of drug concentrations (0.12-128 µg/mL). Minimum Inhibitory Concentration (MIC) values for planktonic cells were ≤2 µg/mL for all strains; however, biofilm-associated MICs, minimum biocidal concentration (MBC), minimum biofilm eradication (MBEC), and minimum biofilm damaging concentration (MBDC) were significantly higher (2-4,119 times). Geometric mean (GM) of MBEC values indicated that MNGX had the highest antifungal activity within Candida species, with a GM-MBEC of 5.9 µg/mL. Despite its overall potency, MNGX was less effective against C. auris biofilms from clade IV strains, where IBF showed superior activity. While not the most potent agent overall, AMB induced the smallest fold-change increases (2- to 32-fold) in biofilm-associated states data compared to planktonic MICs. Conversely, CAS exhibited the lowest activity against Candida spp. biofilms. The eradication of C. auris and C. parapsilosis biofilms required substantially higher concentrations than C. albicans, with some agents, such as RZF and CAS, necessitating up to 42-fold increases in dosage. In conclusion, our in vitro model highlights the antibiofilm activity of novel antifungals against major Candida species, revealing significant differences in efficacy among species. MNGX demonstrated the highest activity, underscoring its potential as a promising candidate for the treatment of biofilm-related infections.

Keywords: Calgary biofilm device; Candida biofilms; antibiofilm activity; novel antifungals.

Fig 1

Representative example of Candida biofilm formation on the Calgary Biofilm Device and plates used for determining MBC, MBEC, and MBDC. At the top, a schematic representation of biofilm formation on the MBEC Assay device is shown. Biofilm formation is observed as a yellow layer on each peg, while white pegs correspond to negative controls. At the bottom, in the challenge plate, released biofilm cells appear turbid in wells with growth, whereas translucent wells indicate no growth. The spot assay shows fungal growth on Sabouraud Dextrose Agar (SDA) after 24 hours of inoculation (5 µL from each well of the recovery plate). Within the black rectangles, hydroxyapatite powder is visible in the agar; this should not be confused with yeast growth. Finally, the MBDC recovery plate with Alamar Blue reveals metabolic activity, with blue indicating metabolic inactivity and pink indicating metabolic activity.

Fig 2

Overall effect of antifungals on planktonic and biofilm-associated cells: base-10 logarithm transformed geometric means of MIC, MBC, MBEC, and MBDC for each Candida species.