Cloning of the lanosterol 14-α-demethylase (ERG11) gene in Trichosporon asahii: a possible association between G453R amino acid substitution and azole resistance in T. asahii

Abstract

Lanosterol 14-α-demethylase ( Erg11 protein; Erg11p ), encoded by the ERG11 gene, is the primary target of azoles. Recently, a change in affinity of this enzyme for azoles has been reported as a resistance mechanism in several fungal species. Trichosporon asahii ( T. asahii) is susceptible to fluconazole (FLC). This report identified the ERG11 gene of T. asahii (NCBI accession; HQ176415). The Erg11p of T. asahii, presumed from the DNA sequence, was closely related to the Erg11p of Cryptococcus neoformans. Furthermore, a FLC-susceptible strain was cultured in medium containing FLC at concentrations from 4.0 to 16 μg mL(-1) in order to analyze the development of FLC resistance in T. asahii. The degree of resistance was related to the FLC concentration of the growth medium. One highly resistant strain that was cultured in the medium containing 16 μg mL(-1) FLC contained 1 point mutation (G1357C) that caused a single amino acid substitution at G453R. This amino acid is highly conserved among major fungal pathogens, and it is in a region very close to the heme-binding domain, which is characteristic of the cytochrome P450 superfamily, the primary target for the azole class of antifungal agents. This amino acid substitution may have caused the high resistance to azoles in T. asahii.

Molecular identification, antifungal resistance and virulence of Cryptococcus neoformans and Cryptococcus deneoformans isolated in Seville, Spain

“…). The glycine change at this specific point has been previously related to fluconazole resistance at equivalent position in Trichosporon spp (G453R) and in C. albicans (G450V) . Here, the presence of this amino acid substitution has been related to an increase in the MIC during the fluconazole exposure.…”

A New Amino Acid Substitution at G150S in Lanosterol 14-&alpha; Demethylase (Erg11 protein) in Multi-azole-resistant <I>Trichosporon asahii</I>

“…Lanosterol 14-α-demethylase(Erg11 protein; Erg11p) , encoded by the ERG11 gene, is the primary target of azoles. Our previous report identified the ERG11 gene of T. asahii(ATCC MYA-1296) (NCBI accession; HQ176415) 21) . In addition, the FLC-susceptible strain of T. asahii, cultured in medium containing highly concentrated FLC, acquired a point mutation(G1357C)that caused a single amino acid substitution at G453R 21) .…”

Study on Antioxidant Enzymatic Activities of Trichosporon asahii

“…In C. neoformans, its Cu, ZnSOD helped to protect fungal cells from macrophages, but was not a virulence factor as well as its catalase [8,9]. In recent years, the incidence of disseminated trichosporonosis caused by Trichosporon asahii increases obviously, accounting for 5-10 % of deep infection of fungus in patients [10]. Moreover, T. asahii is becoming more and more resistant to antifungal drugs [10].…”

“…In recent years, the incidence of disseminated trichosporonosis caused by Trichosporon asahii increases obviously, accounting for 5-10 % of deep infection of fungus in patients [10]. Moreover, T. asahii is becoming more and more resistant to antifungal drugs [10]. Once T. asahii caused disseminated or systemic infection in the body, its mortality could be more than 80 % [11], which making the therapy become more harder.…”

“…Therefore, we hypothesize that T. asahii also has basic antioxidant defense system. Since T. asahii could invade the host and cause serious infections [10], we infer that there may be a connection between its pathogenicity and their capacity to resist or evade the attack of host immune system. To test this hypothesis, we collected 44 T.asahii strains from different sources, and investigated their SOD and catalase activities, then compared and analyzed the results.…”