In vitro activity of cloconazole, sulconazole, butoconazole, isoconazole, fenticonazole, and five other antifungal agents against clinical isolates of Candida albicans and Candida spp

Species distribution and antifungal susceptibility profiles of yeasts isolated from onychomycosis: a cross-sectional study with insights into emerging species

Candida onychomycosis is a common fungal infection affecting the nails, primarily caused by Candida (C.) species. Regarding the increasing trend of Candida onychomycosis and the antifungal resistant phenomenon in recent years, this study aims to evaluate the epidemiological characteristics of Candida onychomycosis, the distribution of emerging species, and the antifungal susceptibility profiles of isolates. Onychomycosis caused by yeast species was confirmed through direct examination and culture of nail scraping among all individuals suspected to have onychomycosis and referred to a medical mycology laboratory between June 2019 and March 2022. Species of yeast isolates were identified using the multiplex PCR and PCR-RFLP methods. The antifungal susceptibility of isolates to common antifungal agents and imidazole drugs was evaluated according to the M-27-A3 CLSI protocol. Among 101 yeast strains isolated from onychomycosis, Candida parapsilosis complex (50.49%) was the most common species, followed by C. albicans (20.79%) and C. tropicalis (10.89%). Rare species of yeasts such as C. guilliermondii and Saccharomyces cerevisiae were also identified by molecular methods. Results obtained from antifungal susceptibility testing showed significant differences in MIC values of isoconazole, fenticonazole, and sertaconazole among different species. Overall, a fluconazole-resistant rate of 3% was found among Candida species. Moreover, there was a statistically significant difference in MICs of fenticonazole and clotrimazole between the two most prevalent causative species, C. parapsilosis complex and C. albicans. Correct identification of the causative agents of onychomycosis and performing susceptibility testing could be helpful in choosing the most appropriate antifungal therapy.

Antifungal susceptibilities, in vitro production of virulence factors and activities of ceragenins against Candida spp. isolated from vulvovaginal candidiasis

Vulvovaginal candidiasis (VVC) is the second most common cause of vaginitis after bacterial vaginosis, affecting millions of women worldwide every year. Candida albicans is the most frequent agent of VVC followed by other species of Candida such as C. glabrata and C. parapsilosis. Out of a total of 100 clinical isolates of Candida spp. obtained from patients diagnosed with VVC, 84 were identified as C. albicans, while the remaining isolates were identified as non--albicans Candida strains. Phospholipases and proteinases were produced by a majority of the C. albicans strains and esterases and hemolysins a minority of these strains. Among the non-C. albicans strains, only a few of the strains produced these proteins. Nearly all of the isolates formed biofilms. Our results showed that the butoconazole, clotrimazole, and fluconazole were active against C. albicans and less so against the non-albicans Candida strains. The MIC90 of amphotericin B and nystatins were 2 and 4 μg/ml, respectively, against either C. albicans or non-albicans Candida spp. Representative ceragenins (CSA-13, CSA-131, and CSA-138), developed as mimics of endogenous antimicrobial peptides, were active against fluconazole-resistant strains, both alone and in combination with fluconazole. These results suggest the potential use of ceragenins in treating VVC, including infections caused by fluconazole-resistant isolates.

Design, Synthesis, and Molecular Docking of 1-(1-(4-Chlorophenyl)-2-(phenylsulfonyl)ethylidene)-2-phenylhydrazine as Potent Nonazole Anticandidal Agent

1-(1-(4-Chlorophenyl)-2-(phenylsulfonyl)ethylidene)-2-phenylhydrazine (13) was designed and synthesized as potential nonazole anticandidal agent and precisely characterized by IR,1H NMR,13C NMR, and ESI-MS. The anti-Candidaactivity of13was evaluated against fourCandidaspecies (C. albicans, C. krusei, C. parapsilosis, andC. glabrata). Compound13displayed good anticandidal activities (MIC=0.39, 0.195, 0.39, and 1.56 μmol/mL, resp.) in comparison with that of the standard drug fluconazole (MIC=0.195, inactive, 1.56, and 1.56 μmol/mL, resp.) againstC. albicans, C. krusei, C. parapsilosis, andC. glabrata, respectively. A molecular modeling of the newly synthesized compound13was built in order to investigate its mode of action towards the prospective target cytochrome P450-dependent enzyme lanosterol 14α-demethylase (PDB-code: 1EA1). The docking results showed a similar binding interaction of13and fluconazole at the active site of CYT P450 14α-sterol demethylase. Furthermore, compound13showed no cytotoxicity against normal human breast cell line MCF10A.

Caenorhabditis elegans-based model systems for antifungal drug discovery

The substantial morbidity and mortality associated with invasive fungal infections constitute undisputed tokens of their severity. The continued expansion of susceptible population groups (such as immunocompromised individuals, patients undergoing extensive surgery, and those hospitalized with serious underlying diseases especially in the intensive care unit) and the limitations of current antifungal agents due to toxicity issues or to the development of resistance, mandate the development of novel antifungal drugs. Currently, drug discovery is transitioning from the traditional in vitro large-scale screens of chemical libraries to more complex bioassays, including in vivo studies on whole animals; invertebrates, such as Caenorhabditis elegans, are thus gaining momentum as screening tools. Key pathogenesis features of fungal infections, including filament formation, are expressed in certain invertebrate and mammalian hosts; among the various potential hosts, C. elegans provides an attractive platform both for the study of host-pathogen interactions and the identification of new antifungal agents. Advantages of compound screening in this facile, relatively inexpensive and not as ethically challenged whole-animal context, include the simultaneous assessment of antifungal efficacy and toxicity that could result in the identification of compounds with distinct mechanisms of action, for example by promoting host immune responses or by impeding fungal virulence factors. With the recent advent of using predictive models to screen for compounds with improved chances of bioavailability in the nematode a priori, high-throughput screening of chemical libraries using the C. elegans-C. albicans antifungal discovery assay holds even greater promise for the identification of novel antifungal agents in the near future.

Conazoles

This review provides a historical overview of the analog based drug discovery of miconazole and its congeners, and is focused on marketed azole antifungals bearing the generic suffix “conazole”. The antifungal activity of miconazole, one of the first broad-spectrum antimycotic agents has been mainly restricted to topical applications. The attractive in vitro antifungal spectrum was a starting point to design more potent and especially orally active antifungal agents such as ketoconazole, itraconazole, posaconazole, fluconazole and voriconazole. The chemistry, in vitro and in vivo antifungal activity, pharmacology, and clinical applications of these marketed conazoles has been described.

Identification of antifungal compounds active against Candida albicans using an improved high-throughput Caenorhabditis elegans assay

Candida albicans, the most common human pathogenic fungus, can establish a persistent lethal infection in the intestine of the microscopic nematode Caenorhabditis elegans. The C. elegans–C. albicans infection model was previously adapted to screen for antifungal compounds. Modifications to this screen have been made to facilitate a high-throughput assay including co-inoculation of nematodes with C. albicans and instrumentation allowing precise dispensing of worms into assay wells, eliminating two labor-intensive steps. This high-throughput method was utilized to screen a library of 3,228 compounds represented by 1,948 bioactive compounds and 1,280 small molecules derived via diversity-oriented synthesis. Nineteen compounds were identified that conferred an increase in C. elegans survival, including most known antifungal compounds within the chemical library. In addition to seven clinically used antifungal compounds, twelve compounds were identified which are not primarily used as antifungal agents, including three immunosuppressive drugs. This assay also allowed the assessment of the relative minimal inhibitory concentration, the effective concentration in vivo, and the toxicity of the compound in a single assay.