Antifungal susceptibility of Aspergillus fumigatus clinical isolates collected from various areas in Japan

Kikuchi, Kazuyo; Watanabe, Akira; Itô, Junko; Oku, Yukio; Wuren, Tuya; Taguchi, Hideaki; Yarita, Kyoko; Muraosa, Yasunori; Yahiro, Maki; Yaguchi, Takashi; Kamei, Katsuhiko

doi:10.1016/j.jiac.2014.01.003

Cited by 26 publications

(13 citation statements)

References 13 publications

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“…MIC test: MICs of each strain against antifungal drugs were investigated as described previously [65]. Tests were performed in triplicates using micafungin, amphotericin B, flucytosine, fluconazole, itraconazole, voriconazole, miconazole, and posaconazole in RPMI 1640 medium (pH 7.0) at 35°C.…”

Section: Methodsmentioning

confidence: 99%

A Novel Zn2-Cys6 Transcription Factor AtrR Plays a Key Role in an Azole Resistance Mechanism of Aspergillus fumigatus by Co-regulating cyp51A and cdr1B Expressions

et al. 2017

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Successful treatment of aspergillosis caused by Aspergillus fumigatus is threatened by an increasing incidence of drug resistance. This situation is further complicated by the finding that strains resistant to azoles, the major antifungal drugs for aspergillosis, have been widely disseminated across the globe. To elucidate mechanisms underlying azole resistance, we identified a novel transcription factor that is required for normal azole resistance in Aspergillus fungi including A. fumigatus, Aspergillus oryzae, and Aspergillus nidulans. This fungal-specific Zn2-Cys6 type transcription factor AtrR was found to regulate expression of the genes related to ergosterol biosynthesis, including cyp51A that encodes a target protein of azoles. The atrR deletion mutant showed impaired growth under hypoxic conditions and attenuation of virulence in murine infection model for aspergillosis. These results were similar to the phenotypes for a mutant strain lacking SrbA that is also a direct regulator for the cyp51A gene. Notably, AtrR was responsible for the expression of cdr1B that encodes an ABC transporter related to azole resistance, whereas SrbA was not involved in the regulation. Chromatin immunoprecipitation assays indicated that AtrR directly bound both the cyp51A and cdr1B promoters. In the clinically isolated itraconazole resistant strain that harbors a mutant Cyp51A (G54E), deletion of the atrR gene resulted in a hypersensitivity to the azole drugs. Together, our results revealed that AtrR plays a pivotal role in a novel azole resistance mechanism by co-regulating the drug target (Cyp51A) and putative drug efflux pump (Cdr1B).

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Section: Methodsmentioning

confidence: 99%

A Novel Zn2-Cys6 Transcription Factor AtrR Plays a Key Role in an Azole Resistance Mechanism of Aspergillus fumigatus by Co-regulating cyp51A and cdr1B Expressions

et al. 2017

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“…All MICs from the isolates were determined as described previously (24). Briefly, the test was performed in triplicate according to a method following the Clinical and Laboratory Standards Institute reference broth microdilution method, document M38-A2 (24), with partial modifications using the dried plate for antifungal susceptibility testing (Eiken Chemicals, Tokyo, Japan) (25). Paecilomyces variotii (ATCC MYA-3630), Candida parapsilosis (ATCC 22019), Candida krusei (ATCC 6258), and Aspergillus flavus (ATCC MYA-3631) were used as quality control or reference strains according the M38-A2 document.…”

Section: Methodsmentioning

confidence: 99%

Drug Sensitivity and Resistance Mechanism in Aspergillus Section Nigri Strains from Japan

Hashimoto

Hagiwara

Watanabe

et al. 2017

Antimicrob Agents Chemother

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Aspergillus niger and its related species, known as Aspergillus section Nigri, are ubiquitously distributed across the globe and are often isolated from clinical specimens. In Japan, Aspergillus section Nigri is second most often isolated from clinical specimens following Aspergillus fumigatus. We determined the species of Aspergillus section Nigri isolated in Japan by DNA sequencing of partial ␤-tubulin genes and investigated drug susceptibility by the CLSI M38-A2 method. The collection contained 20 Aspergillus niger, 59 Aspergillus welwitschiae, and 39 Aspergillus tubingensis strains. Drug susceptibility testing revealed 30 to 55% of A. niger, 6.8 to 18.6% of A. welwitschiae, and 79.5 to 89.7% of A. tubingensis isolates to be less susceptible (socalled resistant) to itraconazole (ITC) and/or voriconazole (VRC) according to the epidemiologic cutoff values (ECVs) proposed for A. niger previously. MIC distributions of ITC or VRC showed no remarkable differences between clinical and environmental isolates. When the cyp51A sequences were compared between susceptible and resistant strains, 18 amino acid mutations were specific for resistant isolates of A. niger and A. tubingensis; however, none of them were confirmed to be associated with azole resistance. Three nonrelated A. welwitschiae isolates possessed a partial deletion in cyp51A, likely attributable to being more susceptible to azoles than other isolates. One of five ITC-resistant A. tubingensis isolates showed higher expression of cyp51A than did susceptible strains. Our results show that cyp51A point mutations may have no association with azole resistance but that in some cases the overexpression of cyp51A may lead to the azole resistance in these species.

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“…The MIC of each antifungal drug against the various A. fumigatus strains was investigated as described previously35. Tests were performed in triplicate using micafungin, amphotericin B, 5-FC, fluconazole, itraconazole, voriconazole, miconazole and posaconazole in RPMI 1640 medium (pH 7.0) at 35 °C.…”

Section: Methodsmentioning

confidence: 99%

Sensitisation of an Azole-Resistant Aspergillus fumigatus Strain containing the Cyp51A-Related Mutation by Deleting the SrbA Gene

Hagiwara

Watanabe

Kamei

2016

Sci Rep

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Azoles are widely used for controlling fungal growth in both agricultural and medical settings. The target protein of azoles is CYP51, a lanosterol 14-α-demethylase involved in the biosynthesis of ergosterol. Recently, a novel azole resistance mechanism has arisen in pathogenic fungal species Aspergillus fumigatus. Resistant strains contain a 34-bp or 46-bp tandem repeat (TR) in the promoter of cyp51A, and have disseminated globally in a short period of time. In this study, we investigated whether an azole-resistant strain with a 46-bp TR (TR46/Y121F/T289A) could be sensitised to azoles by deletion of srbA, encoding a direct regulator of cyp51A. The loss of SrbA did not affect colony growth or conidia production, but decreased expression of cyp51A. The srbA deletion strain showed hyper-susceptibility to medical azoles as well as azole fungicides, while its sensitivity to non-azole fungicides was unchanged. This is the first demonstration that deletion of a regulator of cyp51A can sensitise an azole-resistant A. fumigatus strain. This finding may assist in the development of new drugs to help combat life-threatening azole-resistant fungal pathogens.

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Antifungal susceptibility of Aspergillus fumigatus clinical isolates collected from various areas in Japan

Cited by 26 publications

References 13 publications

A Novel Zn2-Cys6 Transcription Factor AtrR Plays a Key Role in an Azole Resistance Mechanism of Aspergillus fumigatus by Co-regulating cyp51A and cdr1B Expressions

A Novel Zn2-Cys6 Transcription Factor AtrR Plays a Key Role in an Azole Resistance Mechanism of Aspergillus fumigatus by Co-regulating cyp51A and cdr1B Expressions

Drug Sensitivity and Resistance Mechanism in Aspergillus Section Nigri Strains from Japan

Sensitisation of an Azole-Resistant Aspergillus fumigatus Strain containing the Cyp51A-Related Mutation by Deleting the SrbA Gene

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