Exploring antifungal activities of acetone extract of selected Indian medicinal plants against human dermal fungal pathogens

A broad spectrum of medicinal plants was used as traditional remedies for various infectious diseases. Fungal infectious diseases have a significant impact on public health. Fungi cause more prevalent infections in immunocompromised individuals mainly patients undergoing transplantation related therapies, and malignant cancer treatments. The present study aimed to investigate the in vitro antifungal effects of the traditional medicinal plants used in India against the fungal pathogens associated with dermal infections. Indian medicinal plants (Acalypha indica, Lawsonia inermis Allium sativum and Citrus limon) extract (acetone/crude) were tested for their antifungal effects against five fungal species isolated from skin scrapings of fungal infected patients were identified as including Alternaria spp., Curvularia spp., Fusarium spp., Trichophyton spp. and Geotrichum spp. using well diffusion test and the broth micro dilution method. All plant extracts have shown to have antifungal efficacy against dermal pathogens. Particularly, Allium sativum extract revealed a strong antifungal effect against all fungal isolates with the minimum fungicidal concentration (MFC) of 50–100 μg/mL. Strong antifungal activity against Curvularia spp., Trichophyton spp., and Geotrichum spp. was also observed for the extracts of Acalypha indica, and Lawsonia inermis with MFCs of 50–800 μg/mL respectively. The extracts of Citrus limon showed an effective antifungal activity against most of the fungal strains tested with the MFCs of 50–800 μg/mL. Our research demonstrated the strong evidence of conventional plants extracts against clinical fungal pathogens with the most promising option of employing natural-drugs for the treatment of skin infections. Furthermore, in-depth analysis of identifying the compounds responsible for the antifungal activity that could offer alternatives way to develop new natural antifungal therapeutics for combating resistant recurrent infections.     

Photodynamic inactivation for controlling Candida albicans infections

Antimicrobial photodynamic therapy (APDT) combines a non-toxic dye, termed photosensitizer, which is activated by visible light of appropriate wavelength which will produce reactive oxygen species (ROS). These ROS will react with cellular components inducing oxidative processes, leading to cell death. A wide range of microorganisms, have already showed susceptibility to APDT. Therefore, this treatment might consist in an alternative for the management of fungal infections that is mainly caused by biofilms, since they respond poorly to conventional antibiotics and may play a role in persistent infections. Biofilms are the leading cause of microbial infections in humans, thus representing a serious problem in health care. Candida albicans is the main type of fungi able to form biofilms, which cause superficial skin and mucous membrane infections as well as deep-seated mycoses, particularly in immunocompromised patients. In these patients, invasive infections are often associated with high morbidity and mortality. Furthermore, the increase in antifungal resistance has decreased the efficacy of conventional therapies. Treatments are time-consuming and thus demanding on health care budgets. Additionally, current antifungal drugs only have a limited spectrum of action and toxicity. The use of APDT as an antimicrobial topical agent against superficial and cutaneous diseases represents an effective method for eliminating microorganisms.     

Fungicidal effect of pleurocidin by membrane-active mechanism and design of enantiomeric analogue for proteolytic resistance

Pleurocidin (Ple) is a 25-residue peptide which is derived from the skin mucous secretion of the winter flounder (Pleuronectes americanus). In this study, we investigated antifungal effects and its mode of action of Ple on human pathogenic fungi. Ple showed potent antifungal activity with low hemolytic activity. To investigate the antifungal mechanisms of Ple, the cellular localization and membrane interaction of Ple were examined. Protoplast regeneration and membrane-disrupting activity by DPH-labeled membrane support the idea, that Ple exerts fungicidal activity against the human pathogenic fungus Candida albicans with the disruption of a plasma membrane. To aim for which was the application of a therapeutic agent, we designed a synthetic enantiomeric peptide composed of all-d-amino acids to enhance proteolytic resistance. The synthetic all-d-Ple also displayed two-fold more potent antifungal activity than that of all-l-Ple, and its antifungal activity showed proteolytic resistance against various proteases. Therefore, these results suggest a therapeutic potential of all-d-Ple with regard to its proteolytic resistance against human fungal infections.     

Rare Fungal Infections in Children: An Updated Review of the Literature

An increasing trend of reports of rare fungal diseases has been observed to be mainly associated with the substantial increase of high-risk immunocompromised children, as well as with the selective pressure of antifungal drugs. On the other hand, recent reports have shown that several species of these rare fungi may also cause infections in immunocompetent children without obvious underlying conditions. The clinical spectrum of these infections, and most importantly their outcome, varies greatly, implying for a rather heterogenic group of pediatric infections. Various types of superficial and subcutaneous fungal infections, as well as systemic and disseminated life-threatening infections, have been reported. Prompt diagnosis and appropriate treatment of rare fungal diseases in children remains a great challenge. Several treatment options have been used, ranging from localized to combination treatment with extensive surgical excision and long-term antifungal therapy. We review contemporary data of rare fungal infections in pediatric patients focusing on epidemiology, mycology, management and outcome, published during the last three years.     

Hsp21 Potentiates Antifungal Drug Tolerance in Candida albicans

Systemic infections of humans with the fungal pathogen Candida albicans are associated with a high mortality rate. Currently, efficient treatment of these infections is hampered by the relatively low number of available antifungal drugs. We recently identified the small heat shock protein Hsp21 in C. albicans and demonstrated its fundamental role for environmental stress adaptation and fungal virulence. Hsp21 was found in several pathogenic Candida species but not in humans. This prompted us to investigate the effects of a broad range of different antifungal drugs on an Hsp21-null C. albicans mutant strain. Our results indicate that combinatorial therapy targeting Hsp21, together with specific antifungal drug targets, has strong synergistic potential. In addition, we demonstrate that Hsp21 is required for tolerance to ethanol-induced stress and induction of filamentation in response to pharmacological inhibition of Hsp90. These findings might pave the way for the development of new treatment strategies against Candida infections.     

COVID-19 and Fungal infections: a double debacle

Fungal infections remain hardly treatable because of unstandardized diagnostic tests, limited antifungal armamentarium, and more specifically, potential toxic interactions between antifungals and immunosuppressants used during anti-inflammatory therapies, such as those set up in critically ill COVID-19 patients. Taking into account pre-existing difficulties in treating vulnerable COVID-19 patients, any co-occurrence of infectious diseases like fungal infections constitutes a double debacle for patients, healthcare experts, and the public economy. Since the first appearance of SARS-CoV-2, a significant rise in threatening fungal co-infections in COVID-19 patients has been testified in the scientific literature. Better management of fungal infections in COVID-19 patients is, therefore, a priority and requires highlighting common risk factors, relationships with immunosuppression, as well as challenges in fungal diagnosis and treatment. The present review attempts to highlight these aspects in the three most identified causative agents of fungal co-infections in COVID-19 patients: Aspergillus, Candida, and Mucorales species.     

Extensive Deep Dermatophytosis Cause by Trichophyton rubrum in a Patient with Liver Cirrhosis and Chronic Renal Failure

Dermatophytes are the main pathogen of superficial skin fungal infections. On rare occasions, they can cause deep and extensive infections, especially in immunocompromised hosts. We reported a 48-year-old patient with liver cirrhosis and chronic renal failure who developed an extensive deep dermatophytosis with possible hematogenous dissemination. Skin histopathology showed extensive involvement of hair follicles and dermis by fungal elements. The pathogen was cultured from both skin biopsy specimen and central venous line. It was identified as Trichophyton rubrum by morphology and further conformed by sequencing of internal transcribed spacers of ribosomal DNA. The patient died quickly before the identification was available.     

Fungicidal effect of pleurocidin by membrane-active mechanism and design of enantiomeric analogue for proteolytic resistance

Pleurocidin (Ple) is a 25-residue peptide which is derived from the skin mucous secretion of the winter flounder (Pleuronectes americanus). In this study, we investigated antifungal effects and its mode of action of Ple on human pathogenic fungi. Ple showed potent antifungal activity with low hemolytic activity. To investigate the antifungal mechanisms of Ple, the cellular localization and membrane interaction of Ple were examined. Protoplast regeneration and membrane-disrupting activity by DPH-labeled membrane support the idea, that Ple exerts fungicidal activity against the human pathogenic fungus Candida albicans with the disruption of a plasma membrane. To aim for which was the application of a therapeutic agent, we designed a synthetic enantiomeric peptide composed of all-d-amino acids to enhance proteolytic resistance. The synthetic all-d-Ple also displayed two-fold more potent antifungal activity than that of all-l-Ple, and its antifungal activity showed proteolytic resistance against various proteases. Therefore, these results suggest a therapeutic potential of all-d-Ple with regard to its proteolytic resistance against human fungal infections.     

Susceptibility testing of dermatophytes

The dermatophytes are a specialized group of fungi that infect the keratinized tissues of humans (hair, nails, and skin) and cause superficial infections. Although several studies have been conducted to develop methods to determine the susceptibilities of yeast and filamentous fungi, similar studies for dermatophytes have only recently taken place. We review how susceptibility testing of dermatophytes was developed and how it has already been applied to clinical samples. We also review recent advances in the development of disk diffusion and colorimetric methodologies for determining the antifungal susceptibility of dermatophytes. With several agents now available for treating infections due to dermatophytes, susceptibility testing will serve as a valuable tool for clinicians as they choose the most appropriate treatment option. Studies are still needed to establish interpretive breakpoints for antifungal agents used in the treatment of superficial fungal infections.     

Update on Antifungal Resistance and its Clinical Impact

Candida and Aspergillus species are important causes of opportunistic infection in an ever-growing number of vulnerable patients, and these infections are associated with high mortality. This has partly been attributed to the emerging resistance of pathogenic fungi to antifungal therapy, which potentially compromises the management of infected patients. Multi-azole resistance of Aspergillus fumigatus is a current health problem, as well as is the co-resistance of Candida glabrata to both azoles and echinocandins. In most cases, negative clinical consequences of reduced in vitro fungal susceptibility to azoles and/or echinocandins can be traced to acquisition of particular resistance mechanisms. While strategies using antifungal combinations or adjunctive agents that maximize the efficacy of existing antifungals may limit treatment failures, new therapeutic approaches, including antifungal agents with novel mechanisms of action, are urgent. In the meantime, more efforts should be devoted to close monitoring of antifungal resistance and its evolution in the clinical setting.     

pH Signaling in Human Fungal Pathogens: a New Target for Antifungal Strategies

Fungi are exposed to broadly fluctuating environmental conditions, to which adaptation is crucial for their survival. An ability to respond to a wide pH range, in particular, allows them to cope with rapid changes in their extracellular settings. PacC/Rim signaling elicits the primary pH response in both model and pathogenic fungi and has been studied in multiple fungal species. In the predominant human pathogenic fungi, namely, Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, this pathway is required for many functions associated with pathogenesis and virulence. Aspects of this pathway are fungus specific and do not exist in mammalian cells. In this review, we highlight recent advances in our understanding of PacC/Rim-mediated functions and discuss the growing interest in this cascade and its factors as potential drug targets for antifungal strategies. We focus on both conserved and distinctive features in model and pathogenic fungi, highlighting the specificities of PacC/Rim signaling in C. albicans, A. fumigatus, and C. neoformans. We consider the role of this pathway in fungal virulence, including modulation of the host immune response. Finally, as now recognized for other signaling cascades, we highlight the role of pH in adaptation to antifungal drug pressure. By acting on the PacC/Rim pathway, it may therefore be possible (i) to ensure fungal specificity and to limit the side effects of drugs, (ii) to ensure broad-spectrum efficacy, (iii) to attenuate fungal virulence, (iv) to obtain additive or synergistic effects with existing antifungal drugs through tolerance inhibition, and (v) to slow the emergence of resistant mutants.     

Benzimidazole tethered pyrrolo[3,4-b]quinoline with broad-spectrum activity against fungal pathogens

Fungal infections caused by Candida and Cryptococcus are particularly dangerous for immunocompromised individuals. In this study, we identified that benzimidazole fused pyrrolo[3,4-b]quinoline compounds have potent antifungal activity against several clinical isolates of pathogenic fungal strains. Specifically, the compound 6a did not show cytotoxicity against mammalian cells at a concentration that inhibits the growth of fungal strains. In addition, the compound 6a also significantly reduced the metabolic activity of fungal cells in the Candida albicans biofilms. Collectively, our results indicate that benzimidazole fused quinoline compounds have a potential to develop as an antifungal agents.     

AmBisome,tres retos: infección por Candida auris,infección del sistema nervioso central e infección asociada a biopelículas

The treatment of invasive fungal infections remains a challenge, both for the diagnosis and for the need of providing the appropriate antifungal therapy. Candida auris is a pathogenic yeast that is responsible for hospital outbreaks, especially in intensive care units; it is characterized by a high resistance to the antifungal agents and can become multidrug-resistant. At present, the recommended antifungal agents for the invasive infections with this pathogen are echinocandins, always after carrying out an antifungal susceptibility testing. In case of no clinical response or persistent candidemia, the addition of liposomal amphotericin B or isavuconazole may be considered. Both fungal infection of the central nervous system and that associated with biomedical devices remain rare entities affecting mainly immunocompromised patients. However, an increase in their incidence in recent years, along with high morbidity and mortality, has been shown. The treatment of these infections is conditioned by the limited knowledge of the pharmacokinetic properties of antifungals. A better understanding of the pharmacokinetic and pharmacodynamic parameters of the different antifungals is essential to determine the efficacy of the antifungal agents in the treatment of these infections.     

The fungal cell wall as a target for the development of new antifungal therapies

In the past three decades invasive mycoses have globally emerged as a persistent source of healthcare-associated infections. The cell wall surrounding the fungal cell opposes the turgor pressure that otherwise could produce cell lysis. Thus, the cell wall is essential for maintaining fungal cell shape and integrity. Given that this structure is absent in host mammalian cells, it stands as an important target when developing selective compounds for the treatment of fungal infections. Consequently, treatment with echinocandins, a family of antifungal agents that specifically inhibits the biosynthesis of cell wall (1-3)β-D-glucan, has been established as an alternative and effective antifungal therapy. However, the existence of many pathogenic fungi resistant to single or multiple antifungal families, together with the limited arsenal of available antifungal compounds, critically affects the effectiveness of treatments against these life-threatening infections. Thus, new antifungal therapies are required. Here we review the fungal cell wall and its relevance in biotechnology as a target for the development of new antifungal compounds, disclosing the most promising cell wall inhibitors that are currently in experimental or clinical development for the treatment of some invasive mycoses.     

Delivery of Antifungal Agents from Bone Cement

Fungal osteoarticular infections, including prosthetic joint infections and osteomyelitis, are rare yet present a therapeutic challenge with no guidelines to direct optimal treatment. When these infections occur, the majority are due to Candida species. In addition to systemic therapy, adjunctive antifungal-loaded bone cement has been utilized to successfully treat these infections. Amphotericin B is used most commonly, but cases utilizing voriconazole, fluconazole, and itraconazole have been reported as well. In vitro data suggest better elution of voriconazole from bone cement while there is minimal elution of amphotericin B. Unfortunately, a lack of consistency in the methods of both in vitro studies and case reports makes it difficult to determine if the addition of an antifungal agent in bone cement improves outcomes in fungal osteoarticular infections. This article provides an overview of bone cement as a delivery system for antifungal agents in vitro and in clinical reports.     

PARP-1 regulates the expression of caspase-11

Lariciresinol is an enterolignan precursor isolated from the herb Sambucus williamsii, a folk medicinal plant used for its therapeutic properties. In this study, the antifungal properties and mode of action of lariciresinol were investigated. Lariciresinol displays potent antifungal properties against several human pathogenic fungal strains without hemolytic effects on human erythrocytes. To understand the antifungal mechanism of action of lariciresinol, the membrane interactions of lariciresinol were examined. Fluorescence analysis using the membrane probe 3,3′-diethylthio-dicarbocyanine iodide (DiSC₃-5) and 1,6-diphenyl-1,3,5-hexatriene (DPH), as well as a flow cytometric analysis with propidium iodide (PI), a membrane-impermeable dye, indicated that lariciresinol was associated with lipid bilayers and induced membrane permeabilization. Therefore, the present study suggests that lariciresinol possesses fungicidal activities by disrupting the fungal plasma membrane and therapeutic potential as a novel antifungal agent for the treatment of fungal infectious diseases in humans.     

Relevant Animal Models in Dermatophyte Research

Dermatophytoses are common superficial fungal infections affecting both humans and animals. They are provoked by filamentous fungi called dermatophytes specialized in the degradation of keratinized structures, which allows them to induce skin, hair and nail infections. Despite their high incidence, little investigation has been performed for the understanding of these infections compared to fungal opportunistic infections and most of the studies were based on in vitro experiments. The development of animal models for dermatophyte research is required to evaluate new treatments against dermatophytoses or to increase knowledge about fungal pathogenicity factors or host immune response mechanisms. The guinea pig has been the most often used animal model to evaluate efficacy of antifungal compounds against dermatophytes, while mouse models were preferred to study the immune response generated during the disease. Here, we review the relevant animal models that were developed for dermatophyte research and we discuss the advantages and disadvantages of the selected species, especially guinea pig and mouse.     

Fungal cerebral abscess in a diabetic patient successfully treated with surgery followed by prolonged antifungal therapy

BackgroundIntracranial fungal masses are uncommon diseases, but their incidence is increasing, most often due to the prolonged survival of patients with different immunodeficiencies. The management of patients with intracranial fungal masses included stereotactic biopsy for diagnosis, partial or radical surgery excision and prolonged antifungal therapy.AimsWe report the case of a 51-year-old diabetic man with a history of psoas abscess due to Candida albicans 1 year before the onset of neurological symptoms, including headache and generalized tonoclonic seizures.MethodsMagnetic resonance imaging showed a single lesion located in the right parietal lobe with mass effect, surrounding edema and enhancement after injection of gadolinium. The material was purulent.ResultsDirect microscopic examination showed hyaline, branched and septate hyphae compatible with fungal elements.ConclusionsFungal infections, especially due to Candida species, should be considered in diabetic patients with parenchymal brain abscesses. Radical excision followed by prolonged antifungal therapy based on fluconazole or amphotericin B is necessary to improve the prognosis of this type of patients.     

The Changing Face of Dermatophytic Infections Worldwide

Dermatophytes evolve along with the geography and socioeconomic conditions. Epidermophyton floccosum, Microsporum audouinii and Trichophyton schoenleinii acted as the major pathogens of superficial fungal diseases 100 years ago, but their frequency decreased dramatically since the middle of the twentieth century and they are limited to some less-developed countries nowadays; meanwhile, frequency of Trichophyton rubrum, Trichophyton interdigitale, Trichophyton tonsurans and Microsporum canis increased gradually, and these fungi have become the major species globally. Some other dermatophytes, i.e., Trichophyton violaceum, Trichophyton verrucosum and Microsporum ferrugineum, are mainly endemic in some parts of Africa, Asia and Europe. At present, T. rubrum is the leading pathogen for skin and nail fungal infections, whereas M. canis, T. tonsurans and T. violaceum present as the predominant dermatophytes involved in tinea capitis. Population mobility, changes in human lifestyle and advents of antifungal drugs will continually drive the dermatophyte evolution in the skin microenvironment. Comprehensive observation is needed to better understand this kind of organisms and prospect the trends of their changes in future.