Potential of the association of antimicrobial peptides with photodynamic inactivation against Candida albicans

Author(s)

Nathália dos Santos Fusco

• Document type: Master's Dissertation
• Press: Araraquara. 2022-08-02.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araraquara
• Defense date: 2022-06-08
• Advisor: Livia Nordi Dovigo

Abstract

The ability of a microorganism to resist the effects of drugs that were previously able to eliminate it is called microbial resistance. Due to the fact that this phenomenon grows every day, alternative treatments are extremely necessary. Photodynamic inactivation (PDI) and its association with antimicrobial peptides (AMPs) are promising options for inactivating pathogenic microorganisms, however, there are few studies associating this topic against microbial biofilms, in addition, there are no reports in the literature. associating the peptide melittin with the photosensitizer curcumin. Therefore, this study aimed to analyze the effectiveness of these associations for antimicrobial effect by carrying out two studies. The first work was a literature review to map the existing literature about the association of PDI and AMPs, using a systematic search for the selection of articles. Thirty-nine articles were identified through database searches. With the exception of five associations, the vast majority showed antimicrobial efficacy against several susceptible and resistant microorganisms. The second study conducted was a laboratory research aimed at evaluating the efficacy of PAM melittin in association with curcumin-mediated PDI against fluconazole susceptible and resistant strains of Candida albicans. Two reference strains (susceptible and resistant to fluconazole) and two clinical isolates with resistance to fluconazole were used. The minimum fungicidal concentration (MFC) and the minimum inhibitory concentration (MIC) of melittin alone were evaluated for the four strains. From then on, the photophysical characterization of curcumin in the presence and absence of melittin was performed. Analyzes of the antimicrobial effect in planktonic and biofilm samples of only the reference strains were performed. Finally, biofilm samples were analyzed under confocal microscopy to assess the amount of curcumin internalized in biofilms at different exposure times with melittin+curcumin. Data were analyzed with descriptive and inferential statistics, according to the experimental design of each stage (α=0.05). The MIC of melittin was different for each strain (ATCC 90028 - 16μg/mL; ATCC 96901 - 62μg/mL; and both clinical isolates 31 μg/mL). Regarding the evaluations of the antifungal activity of AMP in association with PDI, for ATCC 90028 in planktonic format, both curcumin and melittin promoted a reduction in log values (p<0.0001). When the samples remained in the dark, only melittin had an effect on viability (p≤0.023). When in biofilm, there was a reduction in viability promoted by melittin with exposure to light (p<0.0001). For the ATCC 96901 strain, in planktonic format, there was a reduction in log values when exposed to light for the factors curcumin and melittin alone. As for the biofilm, there was no significant effect on viable colony counts under any condition. Thus, it is concluded that the association of PDI with peptides is capable of promoting a reduction in the viability of pathogenic microorganisms and, specifically, the association melittin+curcumin should be further investigated in order to potentiate the effect of the association against strains of Candida. (AU)

• FAPESP's process: 20/10200-0 - Antifungal potential of peptide LL-37 on C. albicans susceptible and resistant to fluconazole and its effect association with mediated-curcumin photodynamic treatment
• Grantee: Nathália dos Santos Fusco
• Support Opportunities: Scholarships in Brazil - Master