Drug-Resistant Fungi: An Emerging Challenge Threatening Our Limited Antifungal Armamentarium

The high clinical mortality and economic burden posed by invasive fungal infections (IFIs), along with significant agricultural crop loss caused by various fungal species, has resulted in the widespread use of antifungal agents. Selective drug pressure, fungal attributes, and host- and drug-related factors have counteracted the efficacy of the limited systemic antifungal drugs and changed the epidemiological landscape of IFIs. Species belonging to Candida, Aspergillus, Cryptococcus, and Pneumocystis are among the fungal pathogens showing notable rates of antifungal resistance. Drug-resistant fungi from the environment are increasingly identified in clinical settings. Furthermore, we have a limited understanding of drug class-specific resistance mechanisms in emerging Candida species. The establishment of antifungal stewardship programs in both clinical and agricultural fields and the inclusion of species identification, antifungal susceptibility testing, and therapeutic drug monitoring practices in the clinic can minimize the emergence of drug-resistant fungi. New antifungal drugs featuring promising therapeutic profiles have great promise to treat drug-resistant fungi in the clinical setting. Mitigating antifungal tolerance, a prelude to the emergence of resistance, also requires the development of effective and fungal-specific adjuvants to be used in combination with systemic antifungals.

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Herbal Products and Their Active Constituents Used Alone and in Combination with Antifungal Drugs against Drug-Resistant Candida sp.

Antibiotics ◽

10.3390/antibiotics10060655 ◽

2021 ◽

Vol 10 (6) ◽

pp. 655

Author(s):

Anna Herman ◽

Andrzej Przemysław Herman

Keyword(s):

Biofilm Formation ◽

Fungal Infections ◽

Antifungal Drugs ◽

Membrane Transporters ◽

Drug Resistant ◽

Herbal Products ◽

Active Constituents ◽

Over Expression ◽

Candida Sp ◽

Current State

Clinical isolates of Candida yeast are the most common cause of opportunistic fungal infections resistant to certain antifungal drugs. Therefore, it is necessary to detect more effective antifungal agents that would be successful in overcoming such infections. Among them are some herbal products and their active constituents.The purpose of this review is to summarize the current state of knowledge onherbal products and their active constituents havingantifungal activity against drug-resistant Candida sp. used alone and in combination with antifungal drugs.The possible mechanisms of their action on drug-resistant Candida sp. including (1) inhibition of budding yeast transformation into hyphae; (2) inhibition of biofilm formation; (3) inhibition of cell wall or cytoplasmic membrane biosynthesis; (4) ROS production; and (5) over-expression of membrane transporters will be also described.

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A Novel, Rapid, and Low-Volume Assay for Therapeutic Drug Monitoring of Posaconazole and Other Long-Chain Azole-Class Antifungal Drugs

mSphere ◽

10.1128/msphere.00623-18 ◽

2018 ◽

Vol 3 (6) ◽

Cited By ~ 2

Author(s):

Gregory R. Wiedman ◽

Yanan Zhao ◽

David S. Perlin

Keyword(s):

Liquid Chromatography ◽

Therapeutic Drug Monitoring ◽

Human Serum ◽

Drug Monitoring ◽

Fungal Infections ◽

Antifungal Drugs ◽

Therapeutic Drug ◽

Serum Samples ◽

Human Serum Samples ◽

Long Chain

ABSTRACT Clinicians need a better way to accurately monitor the concentration of antimicrobials in patient samples. In this report, we describe a novel, low-sample-volume method to monitor the azole-class antifungal drug posaconazole, as well as certain other long-chain azole-class antifungal drugs in human serum samples. Posaconazole represents an important target for therapeutic drug monitoring (TDM) due to its widespread use in treating invasive fungal infections and well-recognized variability of pharmacokinetics. The current “gold standard” requires trough and peak monitoring through high-pressure liquid chromatography (HPLC) or liquid chromatography-tandem mass spectroscopy (LC-MS/MS). Other methods include bioassays that use highly susceptible strains of fungi in culture plates or 96-well formats to monitor concentrations. Currently, no method exists that is both highly accurate in detecting free drug concentrations and is also rapid. Herein, we describe a new method using reduced graphene oxide (rGO) and a fluorescently labeled aptamer, which can accurately assess clinically relevant concentrations of posaconazole and other long-chain azole-class drugs in little more than 1 h in a total volume of 100 µl. IMPORTANCE This work describes an effective assay for TDM of long-chain azole-class antifungal drugs that can be used in diluted human serum samples. This assay will provide a quick, cost-effective method for monitoring concentrations of drugs such as posaconazole that exhibit well-documented pharmacokinetic variability. Our rGO-aptamer assay has the potential to improve health care for those struggling to treat fungal infections in rural or resource-limited setting.

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Implementation of Pharmacist-driven Antifungal Stewardship Program in A Tertiary Care Hospital

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00629-21 ◽

2021 ◽

Author(s):

Emre Kara ◽

Gokhan Metan ◽

Aygin Bayraktar-Ekincioglu ◽

Dolunay Gulmez ◽

Sevtap Arikan-Akdagli ◽

...

Keyword(s):

Antifungal Therapy ◽

Clinical Pharmacist ◽

Fungal Infections ◽

Tertiary Care ◽

Antifungal Drugs ◽

Care Hospital ◽

Antifungal Stewardship ◽

Inappropriate Use ◽

Stewardship Program ◽

Antifungal Use

Objectives: Antifungal stewardship (AFS) is recommended to reduce the inappropriate use of antifungal drugs. In this study, the role of AFS in providing appropriate antifungal therapy was evaluated. Methods: This study included three periods as observation, feedback/education, and daily AFS activities. In observation period, the use of systemic antifungals was evaluated for a baseline measurement of appropriateness. In second period, monthly meetings were organized to provide feedback and education to physicians regarding antifungal therapy and the rate of adherence to the clinical guidelines. In final period, a clinical pharmacist participated in daily ward rounds to evaluate appropriateness of the antifungal therapy. A scoring system for appropriateness was used for comparison between the three periods. Results: Four hundred and eighteen episodes of antifungal therapy were evaluated. Baseline demographics of patients were similar in all three periods for age, gender, and the number of comorbidities. The indications for antifungal use were for prophylaxis in 22.7%, Candida infections in 58.6%, and invasive mould infections in 18.7%. During the third period, 157 (78.9%) recommendations were made and 151 (96.2%) were accepted. The overall appropriateness of antifungal use increased significantly for prophylaxis (30.8%, 17.9%, 46.3%, p=0.046) and treatment of fungal diseases (27.8%, 32.4%, 71.9%, p<0.001) between the first, second and third periods, respectively. A 30-day mortality was not significantly changed between the three periods (19%, 15.6% and 27.5%; p=0.050). Conclusions: Appropriateness in antifungal therapy can be augmented by the integration of an AFS program. A team-based evaluation of fungal infections and assessment of patients by a clinical pharmacist with a therapeutic perspective may help to increase the quality of antifungal therapy.

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Impact of antifungal resistance in Australia

Microbiology Australia ◽

10.1071/ma07171 ◽

2007 ◽

Vol 28 (4) ◽

pp. 174 ◽

Cited By ~ 5

Author(s):

David Ellis ◽

Tania Sorrell ◽

Sharon Chen

Keyword(s):

Antifungal Activity ◽

Selection Pressure ◽

Opportunistic Infections ◽

Fungal Infections ◽

Fungal Species ◽

Antifungal Drugs ◽

Drug Resistant ◽

Populations At Risk ◽

Complete Resistance ◽

Major Increase

The last two to three decades have seen a major increase in invasive fungal infections (IFIs), a small, but increasing proportion of which are caused by pathogens with partial or complete resistance to antifungal drugs. The increase in IFIs has largely been associated with the increase in immunocompromised and critically ill patients. Opportunistic infections with relatively drug-resistant environmental fungi account for much of the resistance. In addition, amongst the only fungal species to colonise humans, Candida, two species that are resistant (C. krusei) or relatively resistant (C. glabrata) to fluconazole have emerged. In part this is explained by the selection pressure exerted by widespread use of fluconazole. Together with the introduction of new antifungal drugs with selective and/or variable antifungal activity, these changes have stimulated interest in understanding mechanisms and origins of resistance, the identification of resistance in the laboratory and its relationship to clinical outcomes, and in surveillance of clinical isolates and populations at risk of IFIs.

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Antifungal Susceptibility of Dermatophytes Isolated From Cutaneous Fungal Infections: The Vietnamese Experience

Open Access Macedonian Journal of Medical Sciences ◽

10.3889/oamjms.2019.062 ◽

2019 ◽

Vol 7 (2) ◽

pp. 247-249

Author(s):

Chau Van Tro ◽

Khuong Ho Thi Ngoc ◽

Thuong Nguyen Van ◽

Khang Tran Hau ◽

Marco Gandolfi ◽

...

Keyword(s):

Fungal Infections ◽

Antifungal Susceptibility ◽

Antifungal Drugs ◽

Broth Microdilution ◽

Direct Examination ◽

Sensitivity Testing ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Vietnamese Population

AIM: Evaluate the resistance of dermatophytes to systemic antifungal drugs in the Vietnamese population. METHODS: We enrolled 101 patients with cutaneous dermatophytosis at the Dermato-Venereology hospital in HCMC from August 2016 to March 2017. All the specimens were subjected to direct examination (10% KOH mount) and culture on Sabouraud dextrose agar. In vitro antifungal sensitivity testing was done on species isolated from a culture with broth microdilution method. RESULTS: Direct microscopy was positive for dermatophytes in all patients. However this pathogen was found in fungal cultures in only 61.38% of patients. The main causative agent isolated was Trichophyton spp. (90.3%), followed by Microsporum spp. (8%) and Epidermophyton spp. (1.7%). Trichophyton spp. Has shown resistance to fluconazole, griseofulvin, ketoconazole, and itraconazole in 92.9%, 46.4%, 5.4% and 1.8% of strains, respectively. All Microsporum spp. Strains were found resistant to fluconazole and griseofulvin while resistance to ketoconazole was demonstrated in only 20% of strains and none of them was resistant to itraconazole. Epidermophyton spp strains were all resistant to fluconazole, griseofulvin, ketoconazole while none of them was resistant to itraconazole. CONCLUSION: Based upon our results, Itraconazole shows the greatest probability of efficacy in the treatment of cutaneous dermatophytosis in Vietnamese patients.

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Determination of Antifungal MICs by a Rapid Susceptibility Assay

Journal of Clinical Microbiology ◽

10.1128/jcm.38.1.333-340.2000 ◽

2000 ◽

Vol 38 (1) ◽

pp. 333-340

Author(s):

Marcia H. Riesselman ◽

Kevin C. Hazen ◽

Jim E. Cutler

Keyword(s):

Clinical Laboratory ◽

Antifungal Susceptibility ◽

Colorimetric Method ◽

Inoculum Size ◽

Antifungal Drugs ◽

Therapeutic Drug ◽

National Committee ◽

Substrate Uptake ◽

Microtiter Assay ◽

Susceptibility Assay

ABSTRACT A novel microtiter assay for antifungal susceptibility testing was developed. This method has several potential advantages over the M27-A assay of the National Committee for Clinical Laboratory Standards. These include provision of MIC results within 6 to 19 h, graphical display of data, and the availability of objective quantitative endpoints. We refer to the method as the rapid susceptibility assay (RSA). RSA is based on substrate utilization by fungi in the presence of antifungal drugs. Substrate uptake is determined by a colorimetric method, which can be scored by analysis of data obtained from a microplate reader. Variables evaluated in the development of the RSA included inoculum size, incubation period, and efficacy with different classes of antifungal drugs and different yeast isolates. With the rapidly available and quantitative endpoints of the RSA, correlation of MICs and therapeutic drug doses can be evaluated more successfully than they can be evaluated by existing assays.

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Molecular typing and in vitro antifungal susceptibility of Cryptococcus spp from patients in Midwest Brazil

The Journal of Infection in Developing Countries ◽

10.3855/jidc.4446 ◽

2014 ◽

Vol 8 (08) ◽

pp. 1037-1043 ◽

Cited By ~ 13

Author(s):

Olivia Cometti Favalessa ◽

Daphine Ariadne Jesus De Paula ◽

Valeria Dutra ◽

Luciano Nakazato ◽

Tomoko Tadano ◽

...

Keyword(s):

Amphotericin B ◽

Fungal Infections ◽

Antifungal Susceptibility ◽

Cryptococcus Gattii ◽

Antifungal Drugs ◽

Northeastern Brazil ◽

In Vitro Susceptibility ◽

Mato Grosso ◽

Hiv Negative

Introduction: Cryptococcosis is a systemic fungal infection that affects humans and animals, mainly due to Cryptococcus neoformans and Cryptococcus gattii. Following the epidemic of acquired immunodeficiency syndrome (AIDS), fungal infections by C. neoformans have become more common among immunocompromised patients. Cryptococcus gattii has primarily been isolated as a primary pathogen in healthy hosts and occurs endemically in northern and northeastern Brazil. We to perform genotypic characterization and determine the in vitro susceptibility profile to antifungal drugs of the Cryptococcus species complex isolated from HIV-positive and HIV-negative patients attended at university hospitals in Cuiabá, MT, in the Midwestern region of Brazil. Methodology: Micromorphological features, chemotyping with canavanine-glycine-bromothymol blue (CGB) agar and genotyping by URA5-RFLP were used to identify the species. The antifungal drugs tested were amphotericin B, fluconazole, flucytosine, itraconazole and voriconazole. Minimum inhibitory concentrations (MICs) were determined according to the CLSI methodology M27-A3. Results: Analysis of samples yelded C. neoformans AFLP1/VNI (17/27, 63.0%) and C. gattii AFLP6/VGII (10/27, 37.0%). The MICs ranges for the antifungal drugs were: amphotericin B (0.5-1 mg/L), fluconazole (1-16 mg/L), flucytosine (1-16 mg/L), itraconazole (0.25-0.12 mg/L) and voriconazole (0.06-0.5 mg/L). Isolates of C. neoformans AFLP1/VNI were predominant in patients with HIV/AIDS, and C. gattii VGII in HIV-negative patients. The genotypes identified were susceptible to the antifungal drugs tested. Conclusion: It is worth emphasizing that AFLP6/VGII is a predominant genotype affecting HIV-negative individuals in Cuiabá. These findings serve as a guide concerning the molecular epidemiology of C. neoformans and C. gattii in the State of Mato Grosso.

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Anticapsular and Antifungal Activity of α-Cyperone

Antibiotics ◽

10.3390/antibiotics10010051 ◽

2021 ◽

Vol 10 (1) ◽

pp. 51

Author(s):

Connor Horn ◽

Govindsamy Vediyappan

Keyword(s):

Antifungal Activity ◽

Fungal Pathogens ◽

Fungal Infections ◽

Antifungal Drugs ◽

Cyperus Rotundus ◽

Drug Resistant ◽

Fungal Virulence ◽

Medical Needs ◽

Number Of Patients ◽

Immunosuppressed Patients

Fungal infections affect 300 million people and cause 1.5 million deaths globally per year. With the number of immunosuppressed patients increasing steadily, there is an increasing number of patients infected with opportunistic fungal infections such as infections caused by the species of Candida and Cryptococcus. In fact, the drug-resistant Can. krusei and the emerging pan-antifungal resistant Can. auris pose a serious threat to human health as the existing limited antifungals are futile. To further complicate therapy, fungi produce capsules and spores that are resistant to most antifungal drugs/host defenses. Novel antifungal drugs are urgently needed to fill unmet medical needs. From screening a collection of medicinal plant sources for antifungal activity, we have identified an active fraction from the rhizome of Cyperus rotundus, the nut grass plant. The fraction contained α-Cyperone, an essential oil that showed fungicidal activity against different species of Candida. Interestingly, the minimal inhibitory concentration of α-Cyperone was reduced 8-fold when combined with a clinical antifungal drug, fluconazole, indicating its antifungal synergistic potential and could be useful for combination therapy. Furthermore, α-Cyperone affected the synthesis of the capsule in Cryp. neoformans, a causative agent of fungal meningitis in humans. Further work on mechanistic understanding of α-Cyperone against fungal virulence could help develop a novel antifungal agent for drug-resistant fungal pathogens.

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Visible Lights Combined with Photosensitizing Compounds Are Effective against Candida albicans Biofilms

Microorganisms ◽

10.3390/microorganisms9030500 ◽

2021 ◽

Vol 9 (3) ◽

pp. 500 ◽

Cited By ~ 1

Author(s):

Priyanka Bapat ◽

Gurbinder Singh ◽

Clarissa J. Nobile

Keyword(s):

Candida Albicans ◽

Photodynamic Therapy ◽

Biofilm Formation ◽

Fungal Pathogens ◽

Fungal Infections ◽

Therapeutic Strategies ◽

Antifungal Drugs ◽

Clinical Settings ◽

Drug Resistant ◽

Candida Albicans Biofilms

Fungal infections are increasing in prevalence worldwide, especially in immunocompromised individuals. Given the emergence of drug-resistant fungi and the fact that there are only three major classes of antifungal drugs available to treat invasive fungal infections, there is a need to develop alternative therapeutic strategies effective against fungal infections. Candida albicans is a commensal of the human microbiota that is also one of the most common fungal pathogens isolated from clinical settings. C. albicans possesses several virulence traits that contribute to its pathogenicity, including the ability to form drug-resistant biofilms, which can make C. albicans infections particularly challenging to treat. Here, we explored red, green, and blue visible lights alone and in combination with common photosensitizing compounds for their efficacies at inhibiting and disrupting C. albicans biofilms. We found that blue light inhibited biofilm formation and disrupted mature biofilms on its own and that the addition of photosensitizing compounds improved its antibiofilm potential. Red and green lights, however, inhibited biofilm formation only in combination with photosensitizing compounds but had no effects on disrupting mature biofilms. Taken together, these results suggest that photodynamic therapy may be an effective non-drug treatment for fungal biofilm infections that is worthy of further exploration.

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Identification of Promising Antifungal Drugs against Scedosporium and Lomentospora Species after Screening of Pathogen Box Library

Journal of Fungi ◽

10.3390/jof7100803 ◽

2021 ◽

Vol 7 (10) ◽

pp. 803

Author(s):

Rodrigo Rollin-Pinheiro ◽

Luana Pereira Borba-Santos ◽

Mariana Ingrid Dutra da Silva Xisto ◽

Yuri de Castro-Almeida ◽

Victor Pereira Rochetti ◽

...

Keyword(s):

Fungal Infections ◽

Antifungal Susceptibility ◽

Antifungal Drugs ◽

Positive Interactions ◽

Immunocompromised Patients ◽

Planktonic Cells ◽

Morphological Alterations ◽

Susceptibility Tests ◽

Therapeutic Alternatives ◽

Scanning Electron

Fungal infections have been increasing during the last decades. Scedosporium and Lomentospora species are filamentous fungi most associated to those infections, especially in immunocompromised patients. Considering the limited options of treatment and the emergence of resistant isolates, an increasing concern motivates the development of new therapeutic alternatives. In this context, the present study screened the Pathogen Box library to identify compounds with antifungal activity against Scedosporium and Lomentospora. Using antifungal susceptibility tests, biofilm analysis, scanning electron microscopy (SEM), and synergism assay, auranofin and iodoquinol were found to present promising repurposing applications. Both compounds were active against different Scedosporium and Lomentospora, including planktonic cells and biofilm. SEM revealed morphological alterations and synergism analysis showed that both drugs present positive interactions with voriconazole, fluconazole, and caspofungin. These data suggest that auranofin and iodoquinol are promising compounds to be studied as repurposing approaches against scedosporiosis and lomentosporiosis.

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