Precise genome editing underlines the distinct contributions of mutations in ERG11, ERG3, MRR1, and TAC1 genes to antifungal resistance in Candida parapsilosis.

Candida parapsilosis has recently emerged as a major threat due to the worldwide emergence of fluconazole-resistant strains causing clonal outbreaks in hospitals and poses a therapeutic challenge due to the limited antifungal armamentarium. Here, we used precise genome editing using CRISPR-Cas9 to gain further insights into the contribution of mutations in ERG11, ERG3, MRR1, and TAC1 genes and the influence of allelic dosage to antifungal resistance in C. parapsilosis. Seven of the most common amino acid substitutions previously reported in fluconazole-resistant clinical isolates (including Y132F in ERG11) were engineered in two fluconazole-susceptible C. parapsilosis lineages (ATCC 22019 and STZ5). Each mutant was then challenged in vitro against a large array of antifungals, with a focus on azoles. Any possible change in virulence was also assessed in a Galleria mellonella model. We successfully generated a total of 19 different mutants, using CRISPR-Cas9. Except for R398I (ERG11), all remaining amino acid substitutions conferred reduced susceptibility to fluconazole. However, the impact on fluconazole in vitro susceptibility varied greatly according to the engineered mutation, the stronger impact being noted for G583R acting as a gain-of-function mutation in MRR1. Cross-resistance with newer azoles, non-medical azoles, but also non-azole antifungals such as flucytosine, was occasionally noted. Posaconazole and isavuconazole remained the most active in vitro. Except for G583R, no fitness cost was associated with the acquisition of fluconazole resistance. We highlight the distinct contributions of amino acid substitutions in ERG11, ERG3, MRR1, and TAC1 genes to antifungal resistance in C. parapsilosis.

Chemical Composition, Antifungal, Antioxidant, and Hemolytic Activities of Moroccan Thymus capitatus Essential Oil.

This study aimed to define the chemical composition of Moroccan Thymus capitatus essential oil, and to investigate its in vitro antioxidant and antifungal activities against human pathogenic fungi. Chemical analysis using GC-FID and GC-MS system revealed 28 constituents, representing 99 % of total compounds. Oxygenated monoterpenes represented the highest proportion (79.79 %), among which carvacrol (75.73 %) was the predominant compound, followed by linalol (2.26 %). Monoterpene hydrocarbons represented the second major fraction (16.29 %): within them, the predominant constituents were γ-terpinene (5,55 %), ρ-cymene (5,50 %), and ß-caryophyllene (2.73 %). Antioxidant activity was performed by DPPH scavenging, ß-carotene bleaching inhibition, and ferric reducing power. T. capitatus revealed pronounced DPPH radical scavenging activity (IC50=110.53 µg mL-1), strong ferric reducing ability (EC50=644.4 µg mL-1), and a remarkable degree of protection against lipid peroxidation during ß-carotene bleaching inhibition (IC50=251.76 µg mL-1). Antifungal activity was carried out against Candida, Aspergillus, and Rhizopus species by microdilution method. T. capitatus exhibited potent anticandidal activity (MIC=125-500 µg mL-1) and strong inhibition against filamentous fungi (MIC=250-500 µg mL-1). Its hemolytic activity against human erythrocytes had a low toxic effect at concentrations lower than 1250 µg mL-1. The useful antioxidant properties and broad antifungal effect of T. capitatus EO confirm its considerable potential for the food industry and for phytopharmaceutical production.

Is the C-Terminal Domain an Effective and Selective Target for the Design of Hsp90 Inhibitors against Candida Yeast?

Improving the armamentarium to treat invasive candidiasis has become necessary to overcome drug resistance and the lack of alternative therapy. In the pathogenic fungus Candida albicans, the 90-kDa Heat-Shock Protein (Hsp90) has been described as a major regulator of virulence and resistance, offering a promising target. Some human Hsp90 inhibitors have shown activity against Candida spp. in vitro, but host toxicity has limited their use as antifungal drugs. The conservation of Hsp90 across all species leads to selectivity issues. To assess the potential of Hsp90 as a druggable antifungal target, the activity of nine structurally unrelated Hsp90 inhibitors with different binding domains was evaluated against a panel of Candida clinical isolates. The Hsp90 sequences from human and yeast species were aligned. Despite the degree of similarity between human and yeast N-terminal domain residues, the in vitro activities measured for the inhibitors interacting with this domain were not reproducible against all Candida species. Moreover, the inhibitors binding to the C-terminal domain (CTD) did not show any antifungal activity, with the exception of one of them. Given the greater sequence divergence in this domain, the identification of selective CTD inhibitors of fungal Hsp90 could be a promising strategy for the development of innovative antifungal drugs.

Lethal destructive sinusopathy due to amphotericin B-resistant Aspergillus flavus: A case report

Background:The prevalence of pulmonary aspergillosis and the importance of its early diagnosis are recognized. However, non-pulmonary involvement, including the sinuses region, is not frequently reported, and an infection in this area can affect all paranasal sinuses (pansinusopathy), being a rare pathology that affects immunocompromised hosts. Recent studies have highlighted the occurrence of Aspergillus flavus resistant to antifungal therapy. Therefore, a nasal sinus infection by resistant Aspergillus strains in immunocompromised patients may be linked to a high risk of lethality.Case report:We are reporting a resistant A. flavus infection in an allogeneic hematopoietic stem cell transplant recipient with episodes of febrile neutropenia, and prolonged use of various antibacterial drugs and antifungal prophylaxis. The patient underwent brain magnetic resonance, which showed the presence of pansinusopathy, and presented necrosis in the left nasal region. Direct microscopic examination of a sample taken from the nasal mucosa revealed the presence of septate hyphae and conidiophores resembling those of A. flavus, that species being the identification achieved with MALDI-TOF MS. Antifungigram was performed by microdilution in broth (EUCAST-E.DEF. 9.3.2) and E-test, and resistance to amphotericin B was shown in both tests. The patient died after septic shock and hemorrhage.Conclusions:Invasive fungal infections due to amphotericin-B resistant A. flavus may lead to the death of the patient due to an ineffective therapeutic management. Therefore, antifungal susceptibility testing are of utmost importance for administering the proper treatment. (AU)

Antecedentes:La prevalencia de la aspergilosis pulmonar y la importancia de su diagnóstico precoz son ampliamente conocidos; sin embargo, la afectación extrapulmonar no se informa con frecuencia y son pocos los casos documentados de infección de los senos nasales. Una infección en esta área puede alcanzar todos los senos paranasales (pansinusopatía) cuando afecta a pacientes inmunodeprimidos, lo que agrava la enfermedad preexistente. Estudios recientes han destacado la aparición de cepas que muestran resistencia al tratamiento con fármacos antimicóticos. En el paciente inmunodeprimido una infección de los senos nasales por una cepa de Aspergillus resistente implica un alto riesgo de letalidad.Caso clínico:Presentamos un caso de infección por Aspergillus flavus resistente en un receptor de trasplante alogénico de células madre hematopoyéticas, con episodios de neutropenia febril y uso prolongado de diversos fármacos antibacterianos, además de profilaxis antifúngica. Se realizó una resonancia magnética cerebral que reveló la existencia de pansinusopatía con necrosis en la región nasal izquierda. En el examen microscópico directo de la mucosa nasal se observaron hifas tabicadas y la presencia de conidioforos compatibles con Aspergillus flavus; la identificación con el método MALDI-TOF MS arrojó la especie mencionada. El antifungigrama fue realizado por el método de microdilución en caldo (EUCAST-E.DEF. 9.3.2) y E-test; con ambas técnicas el aislamiento mostró resistencia a la anfotericina B. El paciente falleció tras un shock séptico y hemorragia.Conclusiones:Las infecciones fúngicas invasivas por cepas de Aspergillus flavus resistentes a la anfotericina B puede derivar en la muerte del paciente debido a la ineficacia del tratamiento antifúngico. Es por ello que las pruebas de sensibilidad a los antifúngicos son de suma importancia para establecer así el tratamiento correcto. (AU)

Comparación de dos pruebas de aglutinación (Toxolatex y Toxoscreen) en el diagnóstico de la toxoplasmosis: propuesta de inclusión en un programa de control / Comparison of two agglutination tests (toxolatex and toxoscreen) for toxoplasmosis diagnosis: proposal of inclusión in a control program

Este estuio evaluó las pruebas de aglutinación de látex, Toxolatex, Fumouze (TL) y aglutinación directa, Toxoscreen, Biomerieux (TS), mediante la comparación con las pruebas de referencia: prueba de neutralización, dye test (DT) e inmunofluorescencia indirecta (IFI). En los 500 sueros estudiados, se encontró una buena concordancia entre las técnicas estudiadas y las de referencia asi: DT (TL, 96,8 por ciento y TS, 98,6 por ciento e IFI (TL 95,4 por ciento y TS 97,2 por ciento). El TL, además de detectar anticuerpos de clase IgM antitoxoplasma, es una técnica poco costosa y de fácil y rápida realización. Los resultados de este estudio permiten recomendar las pruebas de aglutinación para el tamizaje de anticuerpos específicos antitoxoplasma en los programas de control prenatal y en los estudios seroepidemiológicos