Drug-resistant Fungal Infections Research Articles

A dual-targeting antifungal is effective against multidrug-resistant human fungal pathogens.

Drug-resistant fungal infections pose a significant threat to human health. Dual-targeting compounds, which have multiple targets on a single pathogen, offer an effective approach to combat drug-resistant pathogens, although ensuring potent activity and high selectivity remains a challenge. Here we propose a dual-targeting strategy for designing antifungal compounds. We incorporate DNA-binding naphthalene groups as the hydrophobic moieties into the host defence peptide-mimicking poly(2-oxazoline)s. This resulted in a compound, (Gly0.8Nap0.2)20, which targets both the fungal membrane and DNA. This compound kills clinical strains of multidrug-resistant fungi including Candida spp., Cryptococcus neoformans, Cryptococcus gattii and Aspergillus fumigatus. (Gly0.8Nap0.2)20 shows superior performance compared with amphotericin B by showing not only potent antifungal activities but also high antifungal selectivity. The compound also does not induce antimicrobial resistance. Moreover, (Gly0.8Nap0.2)20 exhibits promising in vivo therapeutic activities against drug-resistant Candida albicans in mouse models of skin abrasion, corneal infection and systemic infection. This study shows that dual-targeting antifungal compounds may be effective in combating drug-resistant fungal pathogens and mitigating fungal resistance.

Borneol serves as an adjuvant agent to promote the cellular uptake of curcumin for enhancing its photodynamic fungicidal efficacy against Candida albicans

Candida albicans (C. albicans), a major opportunistic pathogenic fungus, is known to cause superficial skin infections. Unfortunately, the misuse of antibiotics has led to the emergence of drug resistance in fungi. Antimicrobial photodynamic therapy (aPDT), a non-antibiotic alternative, has shown potential in treating drug-resistant fungal infections. Curcumin is a photodynamically active phytochemical whose photodynamic fungicidal efficacy is largely dependent on its intracellular accumulation. However, curcumin faces challenges in penetrating the cytoplasm due to its poor water solubility and the fungal cell wall. Borneol, another monoterpenoid phytochemical, is known for its ability to enhance drug absorption. In this study, we showed that borneol improved the cellular uptake of curcumin, thereby enhancing its photodynamic fungicidal efficacy against C. albicans. This effect was attributed to borneol's ability to increase cell permeability. Transcriptomic analysis further confirmed that borneol disrupted the normal structure and function of the C. albicans cell wall and membrane, resulting in dysregulated mRNA expression of related genes and ultimately increased cell permeability. As a result, the excessive accumulation of curcumin in C. albicans triggered the overproduction of intracellular ROS upon exposure to blue light. These excessive intracellular ROS disrupted various cellular structures, interfered with essential cellular processes, inhibited biofilm formation and reduced virulence. Remarkably, borneol was also found to enhance curcumin uptake by C. albicans within biofilms, further enhancing the anti-biofilm efficacy of curcumin-mediated aPDT (Cur-aPDT). In conclusion, the results of this study strongly support the potential of borneol as an adjuvant agent to Cur-aPDT in treating superficial cutaneous fungal infections.

Effect of tryptophan position and lysine/arginine substitution in antimicrobial peptides on antifungal action

Every year, the overprescription, misuse, and improper disposal of antibiotics have led to the rampant development of drug-resistant pathogens and, in turn, a significant increase in the number of patients who die of drug-resistant fungal infections. Recently, researchers have begun investigating the use of antimicrobial peptides (AMPs) as next-generation antifungal agents to inhibit the growth of drug-resistant fungi. The antifungal activity of alpha-helical peptides designed using the cationic amino acids containing lysine and arginine and the hydrophobic amino acids containing isoleucine and tryptophan were evaluated using 10 yeast and mold fungi. Among these peptides, WIK-14, which is composed of a 14-mer with tryptophan sequences at the amino terminus, showed the best antifungal activity via transient pore formation and ROS generation. In addition, the in vivo antifungal effects of WIK-14 were investigated in a mouse model infected with drug-resistant Candida albicans. The results demonstrate the potential of AMPs as antifungal agents.

Endophytes: Untapped Source of Antifungal Agents

Abstract: Screening for novel bioactive compounds has become more critical since drugresistant fungal infections have emerged and ethno-medicinal plants have been embarked as antifungal agents. The emphasis on medicinal plants has recently switched to the study of endophytes and their interactions with the host plant and screening of their antifungal activity. Endophytes are an endosymbiotic group of microorganisms that thrive within plant tissues without causing any symptoms or marking their presence. Endophytes have been looked into as potential resources for producing distinctive bioactive substances. The quest for bioactive natural compounds of endophytes isolated from higher plants is receiving a lot of interest from researchers worldwide, as seen by the recent surge in studies and publications on antifungal potential. This review aims to comprehend the role and applications of endophytes as a promising source of antifungal agents and enlighten on their most common mode of action.

Characterization of a selective, iron-chelating antifungal compound that disrupts fungal metabolism and synergizes with fluconazole.

Fungal infections are a growing global health concern due to the limited number of available antifungal therapies as well as the emergence of fungi that are resistant to first-line antimicrobials, particularly azoles and echinocandins. Development of novel, selective antifungal therapies is challenging due to similarities between fungal and mammalian cells. An attractive source of potential antifungal treatments is provided by ecological niches co-inhabited by bacteria, fungi, and multicellular organisms, where complex relationships between multiple organisms have resulted in evolution of a wide variety of selective antimicrobials. Here, we characterized several analogs of one such natural compound, collismycin A. We show that NR-6226C has antifungal activity against several pathogenic Candida species, including C. albicans and C. glabrata, whereas it only has little toxicity against mammalian cells. Mechanistically, NR-6226C selectively chelates iron, which is a limiting factor for pathogenic fungi during infection. As a result, NR-6226C treatment causes severe mitochondrial dysfunction, leading to formation of reactive oxygen species, metabolic reprogramming, and a severe reduction in ATP levels. Using an in vivo model for fungal infections, we show that NR-6226C significantly increases survival of Candida-infected Galleria mellonella larvae. Finally, our data indicate that NR-6226C synergizes strongly with fluconazole in inhibition of C. albicans. Taken together, NR-6226C is a promising antifungal compound that acts by chelating iron and disrupting mitochondrial functions.IMPORTANCEDrug-resistant fungal infections are an emerging global threat, and pan-resistance to current antifungal therapies is an increasing problem. Clearly, there is a need for new antifungal drugs. In this study, we characterized a novel antifungal agent, the collismycin analog NR-6226C. NR-6226C has a favorable toxicity profile for human cells, which is essential for further clinical development. We unraveled the mechanism of action of NR-6226C and found that it disrupts iron homeostasis and thereby depletes fungal cells of energy. Importantly, NR-6226C strongly potentiates the antifungal activity of fluconazole, thereby providing inroads for combination therapy that may reduce or prevent azole resistance. Thus, NR-6226C is a promising compound for further development into antifungal treatment.

Discovery of New Broad-Spectrum Anti-Infectives for Eukaryotic Pathogens Using Bioorganometallic Chemistry.

Drug resistance observed with many anti-infectives clearly highlights the need for new broad-spectrum agents to treat especially neglected tropical diseases (NTDs) caused by eukaryotic parasitic pathogens, including fungal infections. Herein, we show that the simple modification of one of the most well-known antifungal drugs, fluconazole, with organometallic moieties not only improves the activity of the parent drug but also broadens the scope of application of the new derivatives. These compounds were highly effective in vivo against pathogenic fungal infections and potent against parasitic worms such as Brugia, which causes lymphatic filariasis and Trichuris, one of the soil-transmitted helminths that infects millions of people globally. Notably, the identified molecular targets indicate a mechanism of action that differs greatly from that of the parental antifungal drug, including targets involved in biosynthetic pathways that are absent in humans, offering great potential to expand our armamentarium against drug-resistant fungal infections and neglected tropical diseases (NTDs) targeted for elimination by 2030.

Fungicidal Effectiveness of Super-Oxidized Solution In Vitro: Potential Implications for Wound Care

Introduction. Drug-resistant fungal infections in chronic wounds represent a major clinical challenge to clinicians. Fungal infections delay wound healing by prolonging inflammation and encouraging biofilm formation, which protects microbes against host defenses and anti-infective medications. As such, interventions that prevent and control nosocomial fungal infections without interfering with the wound healing process are increasingly required. Although conventional antiseptics can effectively exert fungicidal effects, they also have adverse effects on human cells. SOS is a well-known bactericidal agent that enhances the wound healing process, especially for chronic wounds. However, few studies have evaluated the antimicrobial activity of SOS on fungi. Objective. The objective of this study was to evaluate whether SOS exerts fungicidal activities against common fungal species. Materials and Methods. The efficacy of SOS was tested against 6 fungal species (Candida albicans, Candida auris, Candida tropicalis, Candida parapsilosis, Sporothrix schenckii, Trichophyton mentagrophytes) using an in vitro time-kill assay. Results. SOS achieved 99.9999% reduction of all tested fungi within 1 minute of exposure. Conclusions. This study shows that SOS may be an effective tool for the prevention and control of fungal infections.

The metal chaperone protein MtmA plays important roles in antifungal drug susceptibility in Aspergillus fumigatus.

Drug-resistant fungal infections are emerging as an important clinical problem. In general, antifungal resistance results from increased target expression or mutations within the target protein sequence. However, the molecular mechanisms of non-drug target mutations of antifungal resistance in fungal pathogens remain to be explored. Previous studies indicated that the metal chaperone protein Mtm1 is required for mitochondrial Sod2 activation and responses to oxidative stress in yeast and in the fungal pathogen Aspergillus fumigatus, but there is no report of MtmA-related antifungal resistance. In this study, we found that repressed expression of MtmA (only 10% expression) using a conditional promoter resulted in significantly enhanced itraconazole resistance, which was not the result of highly expressed drug targets Erg11A and Erg11B. Furthermore, we demonstrated that repressed expression of MtmA results in upregulation of a series of multidrug resistance-associated transport genes, which may cause multidrug resistance. Further mechanistic studies revealed that inhibition of MtmA expression led to abnormal activation of the calcium signaling system and prompted persistent nucleation of the calcium signaling transcription factor CrzA. Our findings suggest that the metal chaperone protein MtmA is able to negatively regulate fungal resistance via affecting calcium signaling pathway.

Assessment of solution stability and drug release properties of liposomal curcumin in peritoneal dialysis fluid and its synergistic antibacterial activity with vancomycin

Infectious Peritonitis associated with recurrent and persistent infections is the major cause of technique failure of life-sustaining peritoneal dialysis (PD) therapy used for treating patients with end-stage renal failure (ESRF). The infections -if diagnosed timely- are usually resolved with empiric antibiotic treatment. However, the treatment of infections associated with drug resistant bacteria or fungal infections remains challenging, poses a very serious problem to the health of PD patients, and is the leading cause of mortality and morbidity. Therefore, the development of alternate approaches other than antibiotics are required to keep up with the constantly changing and increasing multiple drug resistance (MDR) of bacterial strains. Curcumin exhibits anti-oxidative/anti-inflammatory potential and remarkable wound healing properties. It also has broad-spectrum anti-bacterial/anti-biofilm effects and its synergistic antibacterial activity with several antibiotics (including those used clinically for the treatment of PD associated infections) is well proven against variety of pathogenic infections including MDR strains. However, poor water-solubility of curcumin (<0.125 mg/L) remains a major barrier to achieve desirable bioavailability and further limit its therapeutic efficacy. Among the various drug carrier strategies, liposomal encapsulation has been found to be most promising mode to remarkably enhance the therapeutic index of curcumin by facilitating its gastric absorption, protecting its enzymatic degradation and allowing its slow release over time for maximum benefits. However, to date, the potential of liposomal curcumin has not been explored for the treatment of PD associated infections. Starting our efforts in this direction, a comprehensive assessment of solution stability and drug release properties of curcumin-loaded liposomal vesicles has been demonstrated in peritoneal dialysis fluid. The results clearly indicated an excellent solution stability of curcumin loaded inside liposome and the formulation affirms the regulated curcumin release enhancing the bioavailability. Further, we evaluated the synergistic antibacterial efficacy of curcumin-loaded liposomal formulation with vancomycin against the Staphylococcus aureus and Escherichia coli – pathogens (known for causing intra-peritoneal infections during PD). This synergy strategy resulted in outstanding improvement in bacterial inhibition efficacy of liposomal curcumin at significantly lowered doses. The results of the present study propose lipocurcumin as a potent antibiotic additive to vancomycin to cure PD-infections caused by antibiotic-resistant bacteria.

Antibacterial and Antifungal Properties of a Novel Antimicrobial Peptide GK-19 and Its Application in Skin and Soft Tissue Infections Induced by MRSA or Candida albicans.

The increasing resistance of human pathogens promotes the development of novel antimicrobial agents. Due to the physical bactericidal mechanism of membrane disruption, antimicrobial peptides are considered as potential therapeutic candidates without inducing microbial resistance. Scorpion venom-derived peptide, Androctonus amoreuxi Antimicrobial Peptide 1 (AamAP1), has been proved to have broad-spectrum antimicrobial properties. However, AamAP1 can induce hemolysis and shows strong toxicity against mammalian cells. Herein, the antimicrobial activity and mechanism of a novel synthetic antimicrobial peptide, GK-19, derived from AamAP1 and its derivatives, was evaluated. Five bacteria and three fungi were used to evaluate the antimicrobial effects of GK-19 in vitro. Scalded mice models combined with skin and soft tissue infections (SSTIs) were used to evaluate its applicability. The results indicated that GK-19 could not only inhibit Gram-positive and Gram-negative bacterial growth, but also kill fungi by disrupting the microbial cell membrane. Meanwhile, GK-19 showed negligible toxicity to mammalian cells, low hemolytic activity and high stability in plasma. Furthermore, in scalded mice models combined with SSTIs induced by either Methicillin-Resistant Staphylococcus aureus (MRSA) or Candida albicans, GK-19 showed significant antimicrobial and healing effects. Overall, it was demonstrated that GK-19 might be a promising drug candidate in the battle against drug-resistant bacterial and fungal infections.

Petrositis caused by fluconazole-resistant candida: case report and literature review

BackgroundPetrositis is a rare and fatal complication associated with otitis media. It is most likely caused by bacterial infections, but in some cases it is caused by fungal infections.Case studyThe case in this report is associated with fungal petrositis. The clinical symptoms are: ear pain from chronic otitis media, severe headache, peripheral facial palsy and diplopia. The case was finally confirmed through imaging of middle ear, bacterial culture, pathology, and blood Metagenomic next-generation sequencing (mNGS) test. The patient was treated with sensitive antifungal drugs.ConclusionDrug treatment is conservative but efficient method in this case. mNGS can provide pathogenic reference, when antibiotic is not efficient enough for fungal infections or drug-resistant fungal infections cases. This allows we to adjust drug use for the treatment.

Multiplex PCR via Microarray a Surrogate for Rapid Molecular Detection of Mycobacterial and Fungal Species Along with Anti-Microbial Resistant Genes, Directly from Clinical Specimens’

Multi drug resistant Mycobacterial and invasive fungal infections imposes immense Global health burden resulting in high morbidity and mortality rates. The biggest delima is the time consuming culture and sensitivity diagnostics i.e 04 to 06 weeks for Mycobacterial and 02 to 04 weeks for fungal infections. The delay in result provision adds up to patient’s miseries especially for resistant cases. Therefore the aim of writing this short commentary was to introduce multiplex PCR via microarray bead hybridization assay. A thorough literature review was found extremely deficient. However, a limited published data concluded this technique as a surrogate for rapid molecular and resistant gene depiction for mycobacterial and fungal species directly from clinical specimens. Another biggest advantage was simultaneous genomics and resistant genes identification for Mycobacterial and Fungal isolates. The resistant genes for 1st line anti tuberculous therapy (ATT), 2nd line ATT and commonly used anti fungals can be detected easily. This cost effective test can be finalized in approximately less than 24 hours. Thus early and accurate management can be timely started for both said infections.

Comparative Transcriptomics Reveal Possible Mechanisms of Amphotericin B Resistance in Candida auris.

Candida auris is an emerging multidrug-resistant human fungal pathogen often refractory to treatment by all classes of antifungal drugs. Amphotericin B (AmB) is a fungicidal drug that, despite its toxic side effects, remains a drug of choice for the treatment of drug-resistant fungal infections, including those caused by C. auris. However, the molecular mechanisms underlying AmB resistance are poorly understood. In this study, we present data that suggests membrane lipid alterations and chromatin modifications are critical processes that may contribute to or cause adaptive AmB resistance in clinical C. auris isolates. To determine the plausible cause of increased AmB resistance, we performed RNA-seq of AmB-resistant and sensitive C. auris isolates. Remarkably, AmB-resistant strains show a pronounced enrichment of genes involved in lipid and ergosterol biosynthesis, adhesion, drug transport as well as chromatin remodeling. The transcriptomics data confirm increased adhesion and reduced lipid membrane permeability of AmB-resistant strains compared to the sensitive isolates. The AmB-resistant strains also display hyper-resistance to cell wall perturbing agents, including Congo red, calcofluor white and caffeine. Additionally, we noticed an increased phosphorylation of Mkc1 cell integrity MAP kinase upon AmB treatment. Collectively, these data identify differences in the transcriptional landscapes of AmB-resistant versus AmB-sensitive isolates and provide a framework for the mechanistic understanding of AmB resistance in C. auris.

Genomic Approaches to Antifungal Drug Target Identification and Validation.

The last several decades have witnessed a surge in drug-resistant fungal infections that pose a serious threat to human health. While there is a limited arsenal of drugs that can be used to treat systemic infections, scientific advances have provided renewed optimism for the discovery of novel antifungals. The development of chemical-genomic assays using Saccharomyces cerevisiae has provided powerful methods to identify the mechanism of action of molecules in a living cell. Advances in molecular biology techniques have enabled complementary assays to be developed in fungal pathogens, including Candida albicans and Cryptococcus neoformans. These approaches enable the identification of target genes for drug candidates, as well as genes involved in buffering drug target pathways. Here, we examine yeast chemical-genomic assays and highlight how such resources can be utilized to predict the mechanisms of action of compounds, to study virulence attributes of diverse fungal pathogens, and to bolster the antifungal pipeline.

Plain language summary: Does a person's age affect how common fungal infections are and how well drugs can kill the infections?

Fungi are types of microbes that include molds and yeasts. Fungal infections can make people ill and can even cause death, especially in older people. They can be treated using antifungal drugs, but some fungi are drug resistant. This means the drug cannot kill the fungi. This is a summary based on a study that looked at fungal samples to find out more about antifungal drug resistance in adults younger than 65 compared with adults aged 65 and older. The study found that one type of drug-resistant fungus, called Candida parapsilosis, was more common in older people than in younger people. Another type, called Aspergillus fumigatus, was more common in younger people than in older people. We also found genetic changes in drug-resistant fungi. These changes could explain why the drugs did not work. We hope that the findings from this study can help scientists create new treatments for drug-resistant fungal infections.

An Effective Strategy to Develop Potent and Selective Antifungal Agents from Cell Penetrating Peptides in Tackling Drug-Resistant Invasive Fungal Infections.

The high mortality rate of invasive fungal infections and quick emergence of drug-resistant fungal pathogens urgently call for potent antifungal agents. Inspired by the cell penetrating peptide (CPP) octaarginine (R8), we elongated to 28 residues poly(d,l-homoarginine) to obtain potent toxicity against both fungi and mammalian cells. Further incorporation of glutamic acid residues shields positive charge density and introduces partial zwitterions in the obtained optimal peptide polymer that displays potent antifungal activity against drug-resistant fungi superior to antifungal drugs, excellent stability upon heating and UV exposure, negligible in vitro and in vivo toxicity, and strong therapeutic effects in treating invasive fungal infections. Moreover, the peptide polymer is insusceptible to antifungal resistance owing to the unique CPP-related antifungal mechanism of fungal membrane penetration followed by disruption of organelles within fungal cells. All these merits imply the effectiveness of our strategy to develop promising antifungal agents.

Synthesis, Antimicrobial Evaluation, and Molecular Modeling Studies of New Thiosemicarbazide-Triazole Hybrid Derivatives of (S)-Naproxen.

The discovery of new antimicrobial molecules is crucial for combating drug-resistant bacterial and fungal infections that pose a dangerous threat to human health. In the current research, we applied a molecular hybridization approach to synthesize original thiosemicarbazide-triazole derivatives starting from (S)-naproxen (7a-7k). After structural characterization using FT-IR, 1 H-NMR, 13 C-NMR, and HR-MS, the obtained compounds were screened for their antimicrobial activities against Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Candida albicans ATCC 10231 and their isolates, as well. Although all compounds were found to be moderate antimicrobial agents, in general, their antibacterial activities were better than antifungal effects. Among the tested compounds, 7j carrying nitrophenyl group on the thiosemicarbazide functionality represented the best MIC value against S. aureus isolate. Finally, molecular docking studies were performed in the active pocket of S. aureus flavohemoglobin to rationalize the obtained biological data.

Short Guanidinium-Functionalized Poly(2-oxazoline)s Displaying Potent Therapeutic Efficacy on Drug-Resistant Fungal Infections.

New antifungals are urgently needed to combat invasive fungal infections, due to limited types of available antifungal drugs and frequently encountered side effects, as well as the quick emergence of drug-resistance. We previously developed amine-pendent poly(2-oxazoline)s (POXs) as synthetic mimics of host defense peptides (HDPs) to have antibacterial properties, but with poor antifungal activity. Hereby, we report the finding of short guanidinium-pendent POXs, inspired by cell-penetrating peptides, as synthetic mimics of HDPs to display potent antifungal activity, superior mammalian cells versus fungi selectivity, and strong therapeutic efficacy in treating local and systemic fungal infections. Moreover, the unique antifungal mechanism of fungal cell membrane penetration and organelle disruption explains the insusceptibility of POXs to antifungal resistance. The easy synthesis and structural diversity of POXs imply their potential as a class of promising antifungal agents.

Design, synthesis and evaluation of novel 5-phenylthiophene derivatives as potent fungicidal of Candida albicans and antifungal reagents of fluconazole-resistant fungi.

A series of 5-phenylthiophene derivatives with novel structures were designed and synthesized to combat the increasing incidence of susceptible and drug-resistant fungal infections. The antifungal activity of the synthesized compounds was assessed against seven susceptible strains and six fluconazole-resistant strains. It is especially encouraging that compounds 17b and 17f displayed significant antifungal activities against all tested strains. Furthermore, the potent compounds 17b and 17f could prevent the formation of fungi biofilms and 17f displayed satisfactory fungicidal activity. Preliminary mechanistic studies showed that the potent antifungal activity of compound 17f stemmed from inhibition of C.albicans CYP51. In addition, Compounds 17b and 17f were almost nontoxic to mammalian A549, MCF-7, and THLE-2cells. These results strongly suggested that compounds 17b and 17f are promising as novel antifungal drugs.

Alternative Treatment Strategies for Secondary Bacterial and Fungal Infections Associated with COVID-19.

Antimicrobials are essential for combating infectious diseases. However, an increase in resistance to them is a major cause of concern. The empirical use of drugs in managing COVID-19 and the associated secondary infections have further exacerbated the problem of antimicrobial resistance. Hence, the situation mandates exploring and developing efficient alternatives for the treatment of bacterial and fungal infections in patients suffering from COVID-19 or other viral infections. In this review, we have described the alternatives to conventional antimicrobials that have shown promising results and are at various stages of development. An acceleration of efforts to investigate their potential as therapeutics can provide more treatment options for clinical management of drug-resistant secondary bacterial and fungal infections in the current pandemic and similar potential outbreaks in the future. The alternatives include bacteriophages and their lytic enzymes, anti-fungal enzymes, antimicrobial peptides, nanoparticles and small molecule inhibitors among others. What is required at this stage is to critically examine the challenges in developing the listed compounds and biomolecules as therapeutics and to establish guidelines for their safe and effective application within a suitable time frame. In this review, we have attempted to highlight the importance of rational use of antimicrobials in patients suffering from COVID-19 and boost the deployment of alternative therapeutics.