Drug Repurposing in Medical Mycology: Identification of Compounds as Potential Antifungals to Overcome the Emergence of Multidrug-Resistant Fungi.

Immunodepression, whether due to HIV infection or organ transplantation, has increased human vulnerability to fungal infections. These conditions have created an optimal environment for the emergence of opportunistic infections, which is concomitant to the increase in antifungal resistance. The use of conventional antifungal drugs as azoles and polyenes can lead to clinical failure, particularly in immunocompromised individuals. Difficulties related to treating fungal infections combined with the time required to develop new drugs, require urgent consideration of other therapeutic alternatives. Drug repurposing is one of the most promising and rapid solutions that the scientific and medical community can turn to, with low costs and safety advantages. To treat life-threatening resistant fungal infections, drug repurposing has led to the consideration of well-known and potential molecules as a last-line therapy. The aim of this review is to provide a summary of current antifungal compounds and their main resistance mechanisms, following by an overview of the antifungal activity of non-traditional antimicrobial drugs. We provide their eventual mechanisms of action and the synergistic combinations that improve the activity of current antifungal treatments. Finally, we discuss drug repurposing for the main emerging multidrug resistant (MDR) fungus, including the Candida auris, Aspergillus or Cryptococcus species.

Development and standardization of a specific real-time PCR assay for the rapid detection of Candida auris.

Candida auris is an emerging multiresistant pathogen causing nosocomial fungal infection. Specific detection and identification are necessary. Our goal is to develop a new qPCR system that enables rapid detection of C. auris, based on a GPI (glycosyl-phosphatidylinositol) protein-encoding gene. This system is reproducible and sensitive with a limit of detection of 13 C. auris CFU/qPCR reaction. The 100% specificity of this system is confirmed on 2073 clinical and environmental samples, 50 different bacterial species, and 9 Candida spp. (70 strains). This system is suitable to correctly identify C. auris infections and to trace its source.

Identification of repositionable drugs with novel antimycotic activity by screening the Prestwick Chemical Library against emerging invasive moulds.

OBJECTIVES: The incidence of severe filamentous fungal infections has increased over the past decade. Some of these filamentous fungi are resistant to available antifungals; it is thus urgent to find new compounds that are active against such life-threatening pathogens. METHODS: In this study, 1280 drugs (Prestwick Chemical Library) were tested against six multidrug-resistant (MDR) filamentous fungi, includingAspergillus, Fusarium, Scedosporium/Lomentospora, Rhizopus and Lichtheimia species. RESULTS: Several hits were identified that induced fungal growth inhibition ≥70%. Among the non-antifungal compounds that were effective against the clinical moulds tested in this study, clioquinol, alexidine dihydrochloride, hexachlorophene and thonzonium bromide displayed a broad activity against all strains tested. CONCLUSION: This study enriches the potential antifungal options that can be used against MDR invasive fungal diseases.

Repurposing of Ribavirin as an Adjunct Therapy against Invasive Candida Strains in an In Vitro Study.

The use of antifungal agents in clinical settings is limited by the appearance of drug resistance and adverse side effects. There is, therefore, an urgent need to develop new drugs to strengthen the treatment of invasive fungal diseases. The aim of this study is to describe the potential repurposing of ribavirin as an adjunct therapy against Candida spp. Primary screening of a Prestwick Chemical library against Candida albicans ATCC 90028 and fluconazole-resistant Candida albicans strains was performed. Subsequently, we evaluated the responses of 100 Candida sp. strains to ribavirin, an antiviral agent, using the broth microdilution method as recommended by CLSI. We checked the involvement of efflux pump activity in the development of ribavirin resistance. We studied time-kill curves and performed a checkerboard assay for a ribavirin-antifungal combination study. Twenty-one nonstandard antifungal compounds were identified, including ribavirin. Ribavirin had antifungal activity in vitro against 63 Candida strains, including strains of C. albicans, C. parapsilosis, and C. tropicalis, with MICs ranging from 0.37 to 3.02 µg/ml, while MICs for C. krusei, C. glabrata, C. lusitaniae, and some C. albicans strains remained high (≥24.16 µg/ml). No relation was observed between efflux pump activity and ribavirin resistance. Ribavirin exhibited fungistatic activity against multidrug-resistant (MDR) C. albicans and fungicidal activity against a C. parapsilosis strain. In addition, ribavirin acted synergistically with azoles against Candida strains for which ribavirin MICs were <24.4 µg/ml. This study highlights the potential clinical application of ribavirin, alone or in association with other antifungal agents, as an adjunct anti-Candida drug.

In vitro polymyxin activity against clinical multidrug-resistant fungi.

Background: Although antifungals are available and usually used against fungal infections, multidrug-resistant (MDR) fungal pathogens are a growing problem for public health. Moreover, fungal infections have become more prevalent nowadays due to the increasing number of people living with immunodeficiency. Thus, previously rarely-isolated and/or unidentified fungal species including MDR yeast and moulds have emerged around the world. Recent works indicate that polymyxin antibiotics (polymyxin B and colistin) have potential antifungal proprieties. Therefore, investigating the in vitro activity of these molecules against clinical multidrug-resistant yeast and moulds could be very useful. Methods: In this study, a total of 11 MDR yeast and filamentous fungal strains commonly reported in clinical settings were tested against polymyxin antibiotics. These include strains belonging to the Candida, Cryptococcus and Rhodotorula yeast genera, along with others belonging to the Aspergillus, Fusarium, Scedosporium, Lichtheimia and Rhizopus mould genera. The fungicidal or fungistatic action of colistin against clinical yeast strains was determined by the time-kill study. Further, a checkerboard assay for its combination with antifungal agents, usually used in clinical practices (amphotericin B, itraconazole, voriconazole), was carried out against multi-drug resistant fungal strains. Results: Polymyxin B and colistin exhibited an antifungal activity against all MDR fungal strains tested with MICs ranging from 16 to 128 µg/ml, except for the Aspergillus species. In addition, colistin has a fungicidal action against yeast species, with minimum fungicidal concentrations ranging from 2 to 4 times MICs. It induces damage to the MDR Candida albicans membrane. A synergistic activity of colistin-amphotericin B and colistin-itraconazole associations against Candida albicans and Lichtheimia corymbifera strains, respectively, and colistin-fluconazole association against Rhodotorula mucilaginosa, was demonstrated using a checkerboard microdilution assay. Conclusion: colistin could be proposed, in clinical practice, in association with other antifungals, to treat life-threatening fungal infections caused by MDR yeasts or moulds.

Colistin- and Carbapenem-Resistant Klebsiella pneumoniae Clinical_Isolates: Algeria.

This study investigates the molecular mechanisms of colistin and carbapenem resistance in Klebsiella pneumoniae ST101 strains. The three K. pneumoniae carried blaCTX-M-15, blaTEM-183, and blaSHV-106 genes and two coharbored blaOXA-48. As for colistin resistance, the isolates had amino acid substitutions in PmrA/B and a truncated mgrB gene in one isolate.