In vivo evaluation of the antifungal activity of sertraline against Aspergillus fumigatus

Repurposing drugs for fungal infections: advantages and limitations

Tweetable abstract Repurposing existing drugs for fungal infections has demonstrated potential in both in vitro and animal models, but there are still obstacles to overcome for clinical application. #antifungal #drugrepurposing #fungalinfections.

Powerful and Real-Time Quantification of Antifungal Efficacy against Triazole-Resistant and -Susceptible Aspergillus fumigatus Infections in Galleria mellonella by Longitudinal Bioluminescence Imaging

Aspergillus fumigatus is an environmental mold that causes life-threatening respiratory infections in immunocompromised patients. The plateaued effectiveness of antifungal therapy and the increasing prevalence of triazole-resistant isolates have led to an urgent need to optimize and expand the current treatment options. For the transition of in vitro research to in vivo models in the time- and resource-consuming preclinical drug development pipeline, Galleria mellonella larvae have been introduced as a valuable in vivo screening intermediate. Despite the high potential of this model, the current readouts of fungal infections in G. mellonella are insensitive, irreproducible, or invasive. To optimize this model, we aimed for the longitudinal quantification of the A. fumigatus burden in G. mellonella using noninvasive bioluminescence imaging (BLI). Larvae were infected with A. fumigatus strains expressing a red-shifted firefly luciferase, and the substrate dosage was optimized for the longitudinal visualization of the fungal burden without affecting larval health. The resulting photon flux was successfully validated for fungal quantification against colony forming units (CFU) analyses, which revealed an increased dynamic range from BLI detection. Comparison of BLI to survival rates and health index scores additionally revealed improved sensitivity for the early discrimination of differences in fungal burdens as early as 1 day after infection. This was confirmed by the improved detection of treatment efficacy against triazole-susceptible and -resistant strains. In conclusion, we established a refined G. mellonella aspergillosis model that enables the noninvasive real-time quantification of A. fumigatus by BLI. This model provides a quick and reproducible in vivo system for the evaluation of treatment options and is in line with 3Rs recommendations. IMPORTANCE Triazole-resistant Aspergillus fumigatus strains are rapidly emerging, and resistant infections are difficult to treat, causing mortality rates of up to 88%. The recent WHO priority list underscores A. fumigatus as one of the most critical fungal pathogens for which innovative antifungal treatment should be (urgently) prioritized. Here, we deliver a Galleria mellonella model for triazole-susceptible and -resistant A. fumigatus infections combined with a statistically powerful quantitative, longitudinal readout of the A. fumigatus burden for optimized preclinical antifungal screening. G. mellonella larvae are a convenient invertebrate model for in vivo antifungal screenings, but so far, the model has been limited by variable and insensitive observational readouts. We show that bioluminescence imaging-based fungal burden quantification outperforms these readouts in reliability, sensitivity, and time to the detection of treatment effects in both triazole-susceptible and -resistant infections and can thus lead to better translatability from in vitro antifungal screening results to in vivo confirmation in mouse and human studies.

Repurposing Benzimidazoles against Causative Agents of Chromoblastomycosis: Albendazole Has Superior In Vitro Activity Than Mebendazole and Thiabendazole

Chromoblastomycosis (CBM) is a neglected human implantation mycosis caused by several dematiaceous fungal species. Currently available therapy is usually associated with physical methods, especially surgery, and with high refractoriness. Therefore, drug discovery for CBM is essential. Drug repositioning is a strategy used to facilitate the discovery of new treatments for several diseases. The aim of this study was to discover substances with antifungal activity against CBM agents from a collection of drugs previously approved for use in human diseases. A screening was performed with the NIH Clinical Collection against Fonsecaea pedrosoi. Ten substances, with clinical applicability in CBM, inhibited fungal growth by at least 60%. The minimum inhibitory concentration (MIC) of these substances was determined against other CBM agents, and the benzimidazoles albendazole, mebendazole and thiabendazole presented the lowest MIC values. The selectivity index, based on MIC and cytotoxicity of these substances, revealed albendazole to be more selective. To investigate a possible synergism of this benzimidazole with itraconazole and terbinafine, the chequerboard method was used. All interactions were classified as indifferent. Our current results suggest that benzimidazoles have repositioning potential against CBM agents. Albendazole seems to be the most promising, since it presented the highest selectivity against all dematiaceous fungi tested.

Development and research progress of anti-drug resistant fungal drugs

With the widespread use of immunosuppressive agents and the increase in patients with severe infections, the incidence of fungal infections worldwide has increased year by year. The fungal pathogens Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus cause a total of more than 1 million deaths each year. Long-term use of antifungal drugs can easily lead to fungal resistance, and the prevalence of drug-resistant fungi is a major global health challenge. In order to effectively control global fungal infections, there is an urgent need for new drugs that can exert effective antifungal activity and overcome drug resistance. We must promote the discovery of new antifungal targets and drugs, and find effective ways to control drug-resistant fungi through different ways, so as to reduce the threat of drug-resistant fungi to human life, health and safety. In the past few years, certain progress has been made in the research and development of antifungal drugs. In addition to summarizing some of the antifungal drugs currently approved by the FDA, this review also focuses on potential antifungal drugs, the repositioned drugs, and drugs that can treat drug-resistant bacteria and fungal infections, and provide new ideas for the development of antifungal drugs in the future.

Evaluation of the synergistic antifungal activity of micafungin and voriconazole plus sertraline against Candida auris

Candida auris is an emerging global public health threat. It is an opportunistic yeast that usually affects critically ill patients in healthcare settings and is characterized by reduced susceptibility to multiple antifungal classes. Combination therapy with antifungals and repurposed drugs is a feasible alternative to overcome this problem. The aim of this study was to examine the in vitro interactions and potential synergy of micafungin (MFG) and voriconazole (VRC) plus the antidepressant sertraline (SRT) against clinical isolates of C. auris. Conventional antifungal testing was first performed with the three drugs according to the CLSI methodology. Drug interactions were determined by the checkerboard microdilution assay using the fractional inhibitory concentration (FIC) index. Synergistic interactions were noted with the combination of MFG and SRT plus VRC with FIC values of 0.37 to 0.49 for some strains. Indifferent interactions were observed when MFG was combined with SRT with just one exception (FIC 0.53). No antagonism was observed for any combination. The combination of VRC with MCF or SRT may be relevant for treating C. auris infections.

Synergism between the Antidepressant Sertraline and Caspofungin as an Approach to Minimise the Virulence and Resistance in the Dermatophyte Trichophyton rubrum

Trichophyton rubrum is responsible for several superficial human mycoses. Novel strategies aimed at controlling this pathogen are being investigated. The objective of this study was to evaluate the antifungal activity of the antidepressant sertraline (SRT), either alone or in combination with caspofungin (CASP). We calculated the minimum inhibitory concentrations of SRT and CASP against T. rubrum. Interactions between SRT and CASP were evaluated using a broth microdilution chequerboard. We assessed the differential expression of T. rubrum cultivated in the presence of SRT or combinations of SRT and CASP. We used MTT and violet crystal assays to compare the effect of SRT alone on T. rubrum biofilms with that of the synergistic combination of SRT and CASP. A human nail infection assay was performed. SRT alone, or in combination with CASP, exhibited antifungal activity against T. rubrum. SRT targets genes involved in the biosyntheses of cell wall and ergosterol. Furthermore, the metabolic activity of the T. rubrum biofilm and its biomass were affected by SRT and the combination of SRT and CASP. SRT alone, or in combination, shows potential as an approach to minimise resistance and reduce virulence.

In Vivo Efficacy of Voriconazole in a Galleria mellonella Model of Invasive Infection Due to Azole-Susceptible or Resistant Aspergillus fumigatus Isolates

Aspergillus fumigatus is an environmental filamentous fungus responsible for life-threatening infections in humans and animals. Azoles are the first-line treatment for aspergillosis, but in recent years, the emergence of azole resistance in A. fumigatus has changed treatment recommendations. The objective of this study was to evaluate the efficacy of voriconazole (VRZ) in a Galleria mellonella model of invasive infection due to azole-susceptible or azole-resistant A. fumigatus isolates. We also sought to describe the pharmacokinetics of VRZ in the G. mellonella model. G. mellonella larvae were infected with conidial suspensions of azole-susceptible and azole-resistant isolates of A. fumigatus. Mortality curves were used to calculate the lethal dose. Assessment of the efficacy of VRZ or amphotericin B (AMB) treatment was based on mortality in the lethal model and histopathologic lesions. The pharmacokinetics of VRZ were determined in larval hemolymph. Invasive fungal infection was obtained after conidial inoculation. A dose-dependent reduction in mortality was observed after antifungal treatment with AMB and VRZ. VRZ was more effective at treating larvae inoculated with azole-susceptible A. fumigatus isolates than larvae inoculated with azole-resistant isolates. The concentration of VRZ was maximal at the beginning of treatment and gradually decreased in the hemolymph to reach a C_min (24 h) between 0.11 and 11.30 mg/L, depending on the dose. In conclusion, G. mellonella is a suitable model for testing the efficacy of antifungal agents against A. fumigatus.

Insight into the antifungals used to address human infection due to Trichosporon spp.: a scoping review

Trichosporonosis infections have been increasing worldwide. Providing adequate treatment for these infections remains a challenge. This scoping review contains information about potential antifungals to treat this pathology. Using online databases, we found 76 articles published between 2010 and 2020 related to this topic. Classic antifungals, molecules and biomolecules, repositioned drugs and natural products have been tested against species of Trichosporon. Experimental research has lacked depth or was limited to in vitro and in vivo tests, so there are no promising new candidates for the clinical treatment of patients with trichosporonosis. Furthermore, most studies did not present appropriate scientific criteria for drug tests, compromising their quality.

Antimicrobial Properties of Antidepressants and Antipsychotics-Possibilities and Implications

The spreading of antibiotic resistance is responsible annually for over 700,000 deaths worldwide, and the prevision is that this number will increase exponentially. The identification of new antimicrobial treatments is a challenge that requires scientists all over the world to collaborate. Developing new drugs is an extremely long and costly process, but it could be paralleled by drug repositioning. The latter aims at identifying new clinical targets of an “old” drug that has already been tested, approved, and even marketed. This approach is very intriguing as it could reduce costs and speed up approval timelines, since data from preclinical studies and on pharmacokinetics, pharmacodynamics, and toxicity are already available. Antidepressants and antipsychotics have been described to inhibit planktonic and sessile growth of different yeasts and bacteria. The main findings in the field are discussed in this critical review, along with the description of the possible microbial targets of these molecules. Considering their antimicrobial activity, the manuscript highlights important implications that the administration of antidepressants and antipsychotics may have on the gut microbiome.

Drug repurposing strategies in the development of potential antifungal agents

Abstract

The morbidity and mortality caused by invasive fungal infections are increasing across the globe due to developments in transplant surgery, the use of immunosuppressive agents, and the emergence of drug-resistant fungal strains, which has led to a challenge in terms of treatment due to the limitations of three classes of drugs. Hence, it is imperative to establish effective strategies to identify and design new antifungal drugs. Drug repurposing is a potential way of expanding the application of existing drugs. Recently, various existing drugs have been shown to be useful in the prevention and treatment of invasive fungi. In this review, we summarize the currently used antifungal agents. In addition, the most up-to-date information on the effectiveness of existing drugs with antifungal activity is discussed. Moreover, the antifungal mechanisms of existing drugs are highlighted. These data will provide valuable knowledge to stimulate further investigation and clinical application in this field.

Key points

• Conventional antifungal agents have limitations due to the occurrence of drug-resistant strains.

• Non-antifungal drugs act as antifungal agents in various ways toward different targets.

• Non-antifungal drugs with antifungal activity are demonstrated as effective antifungal strategies.

Silver(I) and Copper(II) Complexes of 1,10-Phenanthroline-5,6-Dione Against Phialophora verrucosa: A Focus on the Interaction With Human Macrophages and Galleria mellonella Larvae

Phialophora verrucosa is a dematiaceous fungus that causes mainly chromoblastomycosis, but also disseminated infections such as phaeohyphomycosis and mycetoma. These diseases are extremely hard to treat and often refractory to current antifungal therapies. In this work, we have evaluated the effect of 1,10-phenanthroline-5,6-dione (phendione) and its metal-based complexes, [Ag (phendione)2]ClO4 and [Cu(phendione)3](ClO4)2.4H2O, against P. verrucosa, focusing on (i) conidial viability when combined with amphotericin B (AmB); (ii) biofilm formation and disarticulation events; (iii) in vitro interaction with human macrophages; and (iv) in vivo infection of Galleria mellonella larvae. The combination of AmB with each of the test compounds promoted the additive inhibition of P. verrucosa growth, as judged by the checkerboard assay. During the biofilm formation process over polystyrene surface, sub-minimum inhibitory concentrations (MIC) of phendione and its silver(I) and copper(II) complexes were able to reduce biomass and extracellular matrix production. Moreover, a mature biofilm treated with high concentrations of the test compounds diminished biofilm viability in a concentration-dependent manner. Pre-treatment of conidial cells with the test compounds did not alter the percentage of infected THP-1 macrophages; however, [Ag(phendione)2]ClO4 caused a significant reduction in the number of intracellular fungal cells compared to the untreated system. In addition, the killing process was significantly enhanced by post-treatment of infected macrophages with the test compounds. P. verrucosa induced a typically cell density-dependent effect on G. mellonella larvae death after 7 days of infection. Interestingly, exposure to the silver(I) complex protected the larvae from P. verrucosa infection. Collectively, the results corroborate the promising therapeutic potential of phendione-based drugs against fungal infections, including those caused by P. verrucosa.

Is Ferroptosis a Future Direction in Exploring Cryptococcal Meningitis?

Cryptococcal meningitis (CM) is the leading cause of mortality among patients infected with human immunodeficiency virus (HIV). Although treatment strategies for CM are continually being developed, the mortality rate is still high. Therefore, we need to explore more therapeutic strategies that are aimed at hindering its pathogenic mechanism. In the field of CM, several studies have observed rapid iron accumulation and lipid peroxidation within the brain, all of which are hallmarks of ferroptosis, which is a type of programmed cell death that is characterized by iron dependence and lipid peroxidation. In recent years, many studies have confirmed the involvement of ferroptosis in many diseases, including infectious diseases such as Mycobacterium tuberculosis infection and coronavirus disease-2019 (COVID-19). Furthermore, ferroptosis is considered as immunogenic and pro-inflammatory as the ferroptotic cells release damage-associated molecular pattern molecules (DAMPs) and alarmin, both of which regulate immunity and pro-inflammatory activity. Hence, we hypothesize that there might be a relationship between this unique cell death modality and CM. Herein, we review the evidence of ferroptosis in CM and consider the hypothesis that ferroptotic cell death may be involved in the cell death of CM.

A New Antifungal Agent (4-phenyl-1, 3-thiazol-2-yl) Hydrazine Induces Oxidative Damage in Candida albicans

A gradual rise in immunocompromised patients over past years has led to the increasing incidence of invasive fungal infections. Development of effective fungicides can not only provide new means for clinical treatment, but also reduce the occurrence of fungal resistance. We identified a new antifungal agent (4-phenyl-1, 3-thiazol-2-yl), hydrazine (numbered as 31C) which showed high-efficiency, broad-spectrum and specific activities. The minimum inhibitory concentration of 31C against pathogenic fungi was between 0.0625-4 μg/ml in vitro, while 31C had no obvious cytotoxicity to human umbilical vein endothelial cells with the concentration of 4 μg/ml. In addition, 31C of 0.5 μg/ml could exhibit significant fungicidal activity and inhibit the biofilm formation of C. albicans. In vivo fungal infection model showed that 31C of 10 mg/kg significantly increased the survival rate of Galleria mellonella. Further study revealed that 31C-treatment increased the reactive oxygen species (ROS) in C. albicans and elevated the expression of some genes related to anti-oxidative stress response, including CAP1, CTA1, TRR1, and SODs. Consistently, 31C-induced high levels of intracellular ROS resulted in considerable DNA damage, which played a critical role in antifungal-induced cellular death. The addition of ROS scavengers, such as glutathione (GSH), N-Acetyl-L-cysteine (NAC) or oligomeric proanthocyanidins (OPC), dramatically reduced the antifungal activities of 31C and rescued the 31C-induced filamentation defect. Collectively, these results showed that 31C exhibited strong antifungal activity and induced obvious oxidative damage, which indicated that compounds with a structure similar to 31C may provide new sight for antifungal drug development.

Known Antimicrobials Versus Nortriptyline in Candida albicans: Repositioning an Old Drug for New Targets

Candida albicans has the capacity to develop resistance to commonly used antimicrobials, and to solve this problem, drug repositioning and new drug combinations are being studied. Nortriptyline, a tricyclic antidepressant, was shown to have the capacity to inhibit biofilm and hyphae formation, along with the ability to efficiently kill cells in a mature biofilm. To use nortriptyline as a new antimicrobial, or in combination with known drugs to increase their actions, it is important to characterize in more detail the effects of this drug on the target species. In this study, the Candida albicans GRACE™ collection and a Haplo insufficiency profiling were employed to identify the potential targets of nortriptyline, and to classify, in a parallel screening with amphotericin B, caspofungin, and fluconazole, general multi-drug resistance genes. The results identified mutants that, during biofilm formation and upon treatment of a mature biofilm, are sensitive or tolerant to nortriptyline, or to general drug treatments. Gene ontology analysis recognized the categories of ribosome biogenesis and spliceosome as enriched upon treatment with the tricyclic antidepressant, while mutants in oxidative stress response and general stress response were commonly retrieved upon treatment with any other drug. The data presented suggest that nortriptyline can be considered a “new” antimicrobial drug with large potential for application to in vivo infection models.

Galleria mellonella for the Evaluation of Antifungal Efficacy against Medically Important Fungi, a Narrative Review

The treatment of invasive fungal infections remains challenging and the emergence of new fungal pathogens as well as the development of resistance to the main antifungal drugs highlight the need for novel therapeutic strategies. Although in vitro antifungal susceptibility testing has come of age, the proper evaluation of therapeutic efficacy of current or new antifungals is dependent on the use of animal models. Mammalian models, particularly using rodents, are the cornerstone for evaluation of antifungal efficacy, but are limited by increased costs and ethical considerations. To circumvent these limitations, alternative invertebrate models, such as Galleria mellonella, have been developed. Larvae of G. mellonella have been widely used for testing virulence of fungi and more recently have proven useful for evaluation of antifungal efficacy. This model is suitable for infection by different fungal pathogens including yeasts (Candida, Cryptococcus, Trichosporon) and filamentous fungi (Aspergillus, Mucorales). Antifungal efficacy may be easily estimated by fungal burden or mortality rate in infected and treated larvae. The aim of the present review is to summarize the actual data about the use of G. mellonella for testing the in vivo efficacy of licensed antifungal drugs, new drugs, and combination therapies.

Galleria mellonella for the Evaluation of Antifungal Efficacy against Medically Important Fungi, a Narrative Review

The treatment of invasive fungal infections remains challenging and the emergence of new fungal pathogens as well as the development of resistance to the main antifungal drugs highlight the need for novel therapeutic strategies. Although in vitro antifungal susceptibility testing has come of age, the proper evaluation of therapeutic efficacy of current or new antifungals is dependent on the use of animal models. Mammalian models, particularly using rodents, are the cornerstone for evaluation of antifungal efficacy, but are limited by increased costs and ethical considerations. To circumvent these limitations, alternative invertebrate models, such as Galleria mellonella, have been developed. Larvae of G. mellonella have been widely used for testing virulence of fungi and more recently have proven useful for evaluation of antifungal efficacy. This model is suitable for infection by different fungal pathogens including yeasts (Candida, Cryptococcus, Trichosporon) and filamentous fungi (Aspergillus, Mucorales). Antifungal efficacy may be easily estimated by fungal burden or mortality rate in infected and treated larvae. The aim of the present review is to summarize the actual data about the use of G. mellonella for testing the in vivo efficacy of licensed antifungal drugs, new drugs, and combination therapies.

In Vitro Activity of Sertraline, an Antidepressant, Against Antibiotic-Susceptible and Antibiotic-Resistant Helicobacter pylori Strains

Antibiotic resistance of Helicobacter pylori, a spiral bacterium associated with gastric diseases, is a topic that has been intensively discussed in last decades. Recent discoveries indicate promising antimicrobial and antibiotic-potentiating properties of sertraline (SER), an antidepressant substance. The aim of the study, therefore, was to determine the antibacterial activity of SER in relation to antibiotic-sensitive and antibiotic-resistant H. pylori strains. The antimicrobial tests were performed using a diffusion-disk method, microdilution method, and time-killing assay. The interaction between SER and antibiotics (amoxicillin, clarithromycin, tetracycline, and metronidazole) was determined by using a checkerboard method. In addition, the study was expanded to include observations by light, fluorescence, and scanning electron microscopy. The growth inhibition zones were in the range of 19–37 mm for discs impregnated with 2 mg of SER. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) counted for 2–8 µg/mL and 4–8 µg/mL, respectively. The time-killing assay showed the time-dependent and concentration-dependent bactericidal activity of SER. Bacteria exposed to MBCs (but not sub-MICs and MICs ≠ MBCs) underwent morphological transformation into coccoid forms. This mechanism, however, was not protective because these cells after a 24-h incubation had a several-fold reduced green/red fluorescence ratio compared to the control. Using the checkerboard assay, a synergistic/additive interaction of SER with all four antibiotics tested was demonstrated. These results indicate that SER may be a promising anti-H. pylori compound.

Evaluation of the expanding spectrum of sertraline against uncommon fungal pathogens

The emergence of non-Aspergillus mold pathogens has increased notoriously in the last decades with serious health consequences. The options of treatment for these microorganisms often resistant to a wide variety of antifungals is limited. Sertraline is an antidepressant with in vitro and in vivo antifungal properties which has been recently studied as an adjuvant in the treatment of invasive infections. In this study, we evaluated the in vitro interaction of sertraline with voriconazole and amphotericin B against Lomentospora prolificans, Scedosporium spp., Fusarium spp., Paecilomyces spp., Alternaria spp. and Curvularia spp. The minimum inhibitory concentration and minimum fungicidal concentration for sertraline were in the range of 8-32 μg/mL. Sertraline showed antifungal capacity against all fungi tested and synergism in combination with amphotericin B against some strains of Lomentospora prolificans, Scedosporium apiospermum and Alternaria alternata, antagonism with voriconazole against Purpureocillium lilacinum and indifference in both combinations for most of the other strains tested. These results suggest a potential role of sertraline as an adjuvant in the treatment of some of these serious mycoses.