Novel Point Mutations in cyp51A and cyp51B Genes Associated with Itraconazole and Posaconazole Resistance in Aspergillus clavatus Isolates

Abstract

Aspergillus clavatus is a common environmental species known to cause occupational allergic disease in grain handlers. We have recently observed azole-resistant isolates of this fungus as a cause of onychomycosis. To further characterize the cause of resistance, the genes encoding 14 a-sterol demethylase enzyme (cyp51A and cyp51B) were characterized and analyzed in 9 ITC-susceptible isolates and 6 isolates with high minimum inhibitory concentrations (MICs) of clinical (nail and sputum) and environmental A. clavatus strains. We found that six isolates with itraconazole MIC >16 mg/L demonstrated nonsynonymous mutations, including V51I, L378P, E483K, and E506G, and synonymous mutations, including F53F, A186A, Q276Q, and H359H. Moreover, P486S was detected in five strains with ITR MIC >16 mg/L. One mutation, F324S, was detected in an isolate with posaconazole MIC >16 mg/L. The effect of E483K and P486S mutations of CYP51A on azole resistance was further investigated using homology modeling and molecular dynamics. We found that E483K and P486S mutations were located near the ligand access channel of CYP51A that could partly lead to narrowing the entry of the ligand access channels. Therefore, we concluded that E483K and P486S mutations may potentially contribute to the limited access of inhibitors to the binding pocket and therefore confer resistance to azole agents.

Trichophyton rubrum Azole Resistance Mediated by a New ABC Transporter, TruMDR3

“…Several mechanisms have been shown to be involved in nondermatophyte pathogenic fungi. These include the overexpression of the gene encoding lanosterol-14α-demethylase ( erg11 in Candida , cyp51A in Aspergillus ), or its variant (23, 31–33), and the overexpression of several multidrug efflux transporters (31, 33–38). We found in T.…”

A 23 bp cyp51A Promoter Deletion Associated With Voriconazole Resistance in Clinical and Environmental Isolates of Neocosmospora keratoplastica

“…Although VRC induced CYP51A mRNA expression in both Nk994 (group I) and Nk2781 (group II) to a similar extent, the CYP51A expression levels were consistently higher throughout the 4 h induction period (1.6-to 2.2-fold) in Nk2781 (Figure 6A). The ∼6,500-fold increased CYP51A mRNA expression levels suggest that, like in A. fumigatus (Abastabar et al, 2019) and the plant fungal pathogen F. graminearum (Liu et al, 2011;Fan et al, 2013), CYP51A of N. keratoplastica is also a key player in the observed azole resistance phenotype of FSSC species. Sterol biosynthesis of Saccharomycotina species like S. cerevisiae or C. albicans is regulated by the sterol regulatory zinccluster TF Upc2 (Yang et al, 2015;Popp et al, 2017).…”

“…This is despite the fact that most FSSC isolates show relatively low VRC susceptibilities with the majority (369 of 555; 66%) exhibiting a minimum growth inhibitory concentration for VRC (MIC VRC ) of ≥8 mg/l (Espinel-Ingroff et al, 2016). Unlike most other Ascomycetes that have only one CYP51 gene, moulds of the Pezizomycotina clade have two CYP51 paralogues (CYP51A and CYP51B) (Brillowska-Dabrowska et al, 2015;Ruan et al, 2017;Abastabar et al, 2019), and Fusarium and Neocosmospora species also have a third CYP51 paralogue, CYP51C (Liu et al, 2011;Fan et al, 2013). In A. fumigatus, modifications of CYP51A are major contributors to azole resistance (Chowdhary et al, 2017).…”

The Fungal CYP51s: Their Functions, Structures, Related Drug Resistance, and Inhibitors

“…Four mutations of A. flavus CYP51C (S196F, A324P, N423D and V465M) are correlated with voriconazole resistance (Sharma et al, 2018). For A. clavatus CYP51A, E483K and P486S mutations may narrow the azole transport and therefore confer lower susceptibility (Abastabar et al, 2019). As for A. terreus and related species, M217T and M217V mutations of CYP51Ap was found correlating with posaconazole resistance (Zoran et al, 2018).…”