Activity of Novel Ultrashort Cyclic Lipopeptides against Biofilm of Candida albicans Isolated from VVC in the Ex Vivo Animal Vaginal Model and BioFlux Biofilm Model—A Pilot Study

Abstract

In recent years, clinicians and doctors have become increasingly interested in fungal infections, including those affecting the mucous membranes. Vulvovaginal candidiasis (VVC) is no exception. The etiology of this infection remains unexplained to this day, as well as the role and significance of asymptomatic vaginal Candida colonization. There are also indications that in the case of VVC, standard methods of determining drug susceptibility to antifungal drugs may not have a real impact on their clinical effectiveness—which would explain, among other things, treatment failures and relapse rates. The aim of the study was to verify the promising results obtained previously in vitro using standard methods, in a newly developed ex vivo model, using tissue fragments of the mouse vagina. The main goal of the study was to determine whether the selected ultrashort cyclic lipopeptides (USCLs) and their combinations with fluconazole at specific concentrations are equally effective against Candida forming a biofilm directly on the surface of the vaginal epithelium. In addition, the verification was also performed with the use of another model for the study of microorganisms (biofilms) in vitro—the BioFlux system, under microfluidic conditions. The obtained results indicate the ineffectiveness of the tested substances ex vivo at concentrations eradicating biofilm in vitro. Nevertheless, the relatively most favorable and promising results were still obtained in the case of combination therapy—a combination of low concentrations of lipopeptides (mainly linear analogs) with mycostatic fluconazole. Additionally, using BioFlux, it was not possible to confirm the previously obtained results. However, an inhibiting effect of the tested lipopeptides on the development of biofilm under microfluidic conditions was demonstrated. There is an incompatibility between the classic in vitro methods, the newer BioFlux method of biofilm testing, offering many advantages postulated elsewhere, and the ex vivo method. This incompatibility is another argument for the need, on the one hand, to intensify research on the pathomechanism of VVC, and, on the other hand, to verify and maybe modify the standard methods used in the determination of Candida susceptibility.

Our current clinical understanding of Candida biofilms: where are we two decades on?

“…Nevertheless, there are no specific large‐scale studies analogous to those demonstrating the biofilm capacity of Gardnerella vaginalis in bacterial vaginosis, which still creates an element of doubt for clinicians in treating RVVC (64). We are also limited with representative biofilm models of the vaginal environment during VVC to study potential Candida biofilm formation, though innovative pre‐clinical models are available (65). These approaches are essential in providing important knowledge of the pathogenesis and tolerance of yeasts in RVVC, which could support more effective treatments that simply relying on azoles that will eventually fail.…”

How to study biofilms: technological advancements in clinical biofilm research

“…Biofilms can be grown either by binding and forming within the glass chamber alone or by seeding the channels with monolayers of cells ( Tremblay et al., 2015 ). The inlets can also be used to pulse biofilms with antimicrobials ( Naudin et al., 2019 ; Zhang et al., 2019a ; Czechowicz et al., 2022 ). The BiofilmChip is a similar concept to the Bioflux, except it does not have the same plate-type technology.…”