CYP51 Paralogue Structure Is Associated with Intrinsic Azole Resistance in Fungi

Azole antifungals are the main treatment for fungal disease in humans. Many species are intrinsically resistant to azoles—in other words all members of the species are resistant without prior exposure—and we do not understand why.

Drug interactions of azole antifungals

Drug interactions can occur when two or more medications are simultaneously given, and one drug increases or decreases the effectiveness of the other. Azole antifungal agents show a wide range of interactions with other drugs. Failure to recognize a drug–drug interaction may produce harm to the patient, including enhanced toxicity of the concomitantly administered medication. Most of the interactions of azole antifungals are of pharmacokinetic type. This article reviews the clinically relevant drug interactions of commonly used antifungals - fluconazole and itraconazole.

The Impact of Cytochrome P450 3A5 Genotype on Early Tacrolimus Metabolism and Clinical Outcomes in Lung Transplant Recipients

Background Tacrolimus (Tac) is the cornerstone of immunosuppressant therapy after lung transplantation (LTx). It shows great inter-individual variability in pharmacokinetics, which could partly be explained by pharmacogenetic factors. Objective We aim to investigate the effect of cytochrome P450 3A5 (CYP3A5) (rs776746) genotypes on early post-operative Tac metabolism and clinical outcomes in LTx recipients. Methods 90 recipients who underwent LTx from 2017 to 2019 at our institution were enrolled in the study. The effect of CYP3A5 genotype on Tac concentration, dose, dose adjusted concentration (C/D) and interaction with azole antifungals were assessed during week 1–4 after transplantation. Associations between CYP3A5 genotype and the incidence of acute kidney injury (AKI), length of hospital stay and mortality were analyzed. Results CYP3A5*1 carriers had lower C/D than CYP3A5*3/*3 group at all time points (p < 0.05). To reach comparable blood concentrations, CYP3A5*1 carriers required higher doses compared with CYP3A5*3/*3 group (p < 0.05). Use of azole antifungals did not blunt the effect of CYP3A5 genotypes on Tac metabolism. Logistic regression showed Tac concentration at week 1, not CYP3A5 genotype, was associated with the incidence of AKI. No statistically significant difference was found between CYP3A5 genotypes and the length of hospital stay (48 (37–68) vs 46(32–57) days, p = 0.264). Kaplan–Meier analysis showed no statistically significant difference between 30-day or 1-year mortality and CYP3A5 genotype. Conclusion CYP3A5 genotype could affect Tac metabolism early after LTx. However, it has no influence on the incidence of AKI, length of hospital stay and mortality.

A Case Report on Mucormycosis in Non-Diabetic, Non-Covid Recovered Patient with no History of Steroid use

Rhino cerebral orbital mucormycosis is an aggressively spreading fungal infection caused by filamentous fungi of the Mucoraceae family and is found to be more prone in patients with comorbidities that include: uncontrolled diabetes mellitus, immune-suppressed patients, iron and aluminum overload, chronic steroid therapy, severe trauma, and protein-energy malnutrition. A 51year old male patient was admitted to the hospital with a complaint of headache and intermittent fever. The patient had no history of diabetes or denovo hypertension. Based on the analysis of histopathological and radiological investigations, the patient was diagnosed with mucormycosis. The patient furthermore underwent an endoscopic surgical debridement followed by standard treatment including antifungal antibiotic(amphotericin-B) and azole antifungals (posaconazole) along with symptomatic treatment. Though the patient was given all possible therapy available, no improvement was seen in the patient's condition (poor prognosis).

MFS1, a Pleiotropic Transporter in Dermatophytes That Plays a Key Role in Their Intrinsic Resistance to Chloramphenicol and Fluconazole

A recently identified Trichophyton rubrum major facilitator superfamily (MFS)-type transporter (TruMFS1) has been shown to give resistance to azole compounds and cycloheximide (CYH) when overexpressed in Saccharomyces cerevisiae. We investigated the roles of MFS1 in the intrinsic resistance of dermatophytes to CYH and chloramphenicol (CHL), which are commonly used to isolate these fungi, and to what extent MFS1 affects the susceptibility to azole antifungals. Susceptibility to antibiotics and azoles was tested in S. cerevisiae overexpressing MFS1 and ΔMFS1 mutants of Trichophyton benhamiae, a dermatophyte that is closely related to T. rubrum. We found that TruMFS1 functions as an efflux pump for CHL in addition to CYH and azoles in S. cerevisiae. In contrast, the growth of T. benhamiae ΔMFS1 mutants was not reduced in the presence of CYH but was severely impaired in the presence of CHL and thiamphenicol, a CHL analog. The suppression of MFS1 in T. benhamiae also increased the sensitivity of the fungus to fluconazole and miconazole. Our experiments revealed a key role of MFS1 in the resistance of dermatophytes to CHL and their high minimum inhibitory concentration for fluconazole. Suppression of MFS1 did not affect the sensitivity to CYH, suggesting that another mechanism was involved in resistance to CYH in dermatophytes.

PDR Transporter ABC1 Is Involved in the Innate Azole Resistance of the Human Fungal Pathogen Fusarium keratoplasticum

Fusarium keratoplasticum is arguably the most common Fusarium solani species complex (FSSC) species associated with human infections. Invasive fusariosis is a life-threatening fungal infection that is difficult to treat with conventional azole antifungals. Azole drug resistance is often caused by the increased expression of pleiotropic drug resistance (PDR) ATP-binding cassette (ABC) transporters of the ABCG sub-family. Most investigations of Fusarium ABC transporters associated with azole antifungal drug resistance are limited to plant pathogens. Through the manual curation of the entire ABCG protein family of four FSSC species including the fully annotated genome of the plant pathogen Nectria haematococca we identified PDR transporters ABC1 and ABC2 as the efflux pump candidates most likely to be associated with the innate azole resistance phenotype of Fusarium keratoplasticum. An initial investigation of the transcriptional response of logarithmic phase F. keratoplasticum cells to 16 mg/L voriconazole confirmed strong upregulation (372-fold) of ABC1 while ABC2 mRNA levels were unaffected by voriconazole exposure over a 4 h time-period. Overexpression of F. keratoplasticum ABC1 and ABC2 in the genetically modified Saccharomyces cerevisiae host ADΔΔ caused up to ∼1,024-fold increased resistance to a number of xenobiotics, including azole antifungals. Although ABC1 and ABC2 were only moderately (20% and 10%, respectively) expressed compared to the Candida albicans multidrug efflux pump CDR1, overexpression of F. keratoplasticum ABC1 caused even higher resistance levels to certain xenobiotics (e.g., rhodamine 6G and nigericin) than CDR1. Our investigations suggest an important role for ABC1 orthologues in the innate azole resistance phenotype of FSSC species.