P012 Antibiofilm activity of staphylococcal peptide derivative(s) against Candida auris biofilms in vitro and in an animal model of catheter-associated infection

Abstract Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM Objectives Candida auris has emerged as a major multidrug-resistant nosocomial pathogen worldwide. The organism exhibits a persistent, colonizing phenotype, usually associated with biofilm formation on hospital surfaces, medical equipment, and indwelling medical devices. Biofilm formation by C. auris can further aggravate the infection acquisition and outcome, owing to the intrinsic resistance of biofilms to disinfectants, antiseptics, and antifungal drugs. The present study aimed to evaluate the preventive and therapeutic efficacy of select peptide derivative(s) from staphylococci against C. auris biofilms in vitro and in a mouse model of C. auris catheter-associated infection. Methods Three potentially antimicrobial, staphylococcal alpha-helical amphipathic peptides (19-23 amino acids) were evaluated for antifungal and antibiofilm activity against clinical isolates of C. auris. The antifungal activity against C. auris planktonic cells was tested by broth microdilution assay according to the method of the Clinical and Laboratory Standards Institute. Biofilm assays were performed in 96 well, flat-bottomed microtiter plates in RPMI-1640, and the effect of the test agents on biofilm formation (MBPC, minimum biofilm preventive concentration) as well as pre-formed biofilms (MBIC, minimum biofilm inhibitory concentration) was determined by subjecting to a two-fold dilution range of the test agents (0.03-64 μm) for 24 h at 37°C, followed by XTT dye reduction test. Field-Emission Scanning Electron Microscopy was performed to observe the effect of peptides on biofilm morphology. The cytotoxicity of these compounds was elucidated on HeLa, HEK-293, and Raw 264.7 murine macrophages by MTT reduction test. The synergistic effect of the selected peptide with representative antifungal drugs belonging to three different classes (amphotericin B, caspofungin, and voriconazole) was tested by fractional inhibitory concentration assays. In vivo activity of the selected peptide was determined in a murine model of subcutaneous C. auris catheter-associated infection, alone and in combination with amphotericin B and caspofungin. Results Based on the antimicrobial activity, antibiofilm activity, and cytotoxicity data, the 19 amino acid, alpha helical staphylococcal peptide derivative (charge, +3; hydrophobicity, 0.634, and hydrophobic moment, 0.623) exhibited promising activity against C. auris biofilms. The peptide was particularly effective in preventing C. auris biofilm formation, with a median MBPC50 of 1 μm. It demonstrated synergistic activity with amphotericin B (FIC index, 0.3) as well as caspofungin (FIC index, 0.18), and an additive effect with voriconazole (FIC index, 0.71). When combined with 0.125 μm of the peptide derivative, nearly 4-to-8-fold lower amount of the drug was required to achieve results comparable to the drug-only controls. Furthermore, nearly 99% reduction in biofilm formation was noted at clinically-achievable trough levels of amphotericin B or caspofungin in combination with this peptide derivative. Similar results were noted in vivo, with nearly 99% reduction in biofilm formation of C. auris in catheter lumen using combination therapy with 0.125 μm of the peptide. Conclusion The present study demonstrates that a 19 amino acid, alpha helical staphylococcal peptide derivative exhibits promising antibiofilm activity against C. auris, particularly in preventing biofilm formation, in vitro and in a murine model of subcutaneous catheter-associated infection.