Overall, 236 Aspergillus spp. isolates identified from clinical specimens in patients with suspected invasive Aspergillus spp. infection underwent susceptibility testing (Table 1). The most frequent species identified were A. fumigatus complex (n = 119), Aspergillus flavus (n = 35), Aspergillus terreus (n = 32), and Aspergillus niger (n = 29). Other uncommon species identified (n = 21) included A. nidulans, A. calidoustus, A. sydowii, A. ochraceus, A. viridinutans, A. insuetus, A. unguis, A. ustus, A. wisconsinensis, A. lentulus, and A. oryzae. Most of these were identified using molecular techniques. For all Aspergillus spp., MIC50/90 values for voriconazole, posaconazole, itraconazole, and isavuconazole were 0.25/1, 0.25/0.5, 0.25/0.5, and 0.5/2 mg/L respectively. Azole antifungals tested against A. fumigatus complex demonstrated favourable in vitro activity overall, with voriconazole, posaconazole, itraconazole, and isavuconazole susceptibility rates of 95%, 92%, 99%, and 100% respectively.
Table 1
Minimum inhibitory concentration (MIC) values for Aspergillus species (n = 236)
Species | Minimum inhibitory concentrations (mg/L) | MIC50 | MIC90 | Susceptible (%) EUCAST breakpoint |
| ≤ 0.008 | 0.015 | 0.03 | 0.06 | 0.125 | 0.25 | 0.5 | 1 | 2 | 4 | 8 | ≥ 16 | Total | | | |
Amphotericin B (n = 236) | 2 | 4 | |
A. fumigatus complex | | | | 2 | 3 | 10 | 15 | 24 | 63 | 2 | | | 119 | | | 47 |
A. flavus | | | | | | | 1 | 9 | 18 | 7 | | | 35 | | | NB |
A. terreus | | | | | | | 2 | 5 | 15 | 10 | | | 32 | | | NB |
A. niger | | | | 1 | 1 | 2 | 2 | 17 | 6 | | | | 29 | | | 79 |
Other Aspergillus spp. | | | | | | 1 | 1 | 3 | 9 | 5 | 2 | | 21 | | | NB |
Voriconazole (n = 234) | 0.25 | 1 | |
A. fumigatus complex | | | | 4 | 14 | 65 | 25 | 3 | 4 | 1 | 1 | | 117 | | | 95 |
A. flavus | | | | | | 9 | 16 | 10 | | | | | 35 | | | NB |
A. terreus | | | | 1 | 3 | 17 | 11 | | | | | | 32 | | | NB |
A. niger | | | | 1 | 2 | 4 | 16 | 5 | | | 1 | | 29 | | | NB |
Other Aspergillus spp. | | | | 2 | 3 | 2 | 2 | 5 | | 4 | 3 | | 21 | | | NB |
Posaconazole (n = 217) | 0.25 | 0.5 | |
A. fumigatus complex | 2 | 4 | 4 | 4 | 47 | 39 | 7 | 3 | | | | | 110 | | | 92 |
A. flavus | | | | | 6 | 20 | 6 | | | | | | 32 | | | NB |
A. terreus | | | 1 | 3 | 19 | 6 | | | | | | | 29 | | | 100 |
A. niger | | 1 | | 2 | | 15 | 9 | | | | | | 27 | | | NB |
Other Aspergillus spp. | | 1 | | 1 | 1 | 2 | 8 | 2 | 3 | | | 1 | 19 | | | NB |
Itraconazole (n = 236) | 0.25 | 0.5 | |
A. fumigatus complex | | 2 | 2 | 3 | 8 | 58 | 40 | 5 | 1 | | | | 119 | | | 99 |
A. flavus | | | | | 2 | 27 | 6 | | | | | | 35 | | | 100 |
A. terreus | | | 2 | 1 | 9 | 20 | | | | | | | 32 | | | 100 |
A. niger | | | | 1 | | 2 | 19 | 6 | 1 | | | | 29 | | | NB |
Other Aspergillus spp. | | | 1 | | 3 | 3 | 6 | 8 | | | | | 21 | | | NB |
Isavuconazole (n = 40) | 0.5 | 2 | |
A. fumigatus complex | | | | 1 | | 4 | 15 | 3 | 1 | | | | 24 | | | 100 |
A. flavus | | | | | | 1 | 1 | | | | | | 2 | | | 100 |
A. terreus | | | | | 1 | 1 | | | | | | | 3 | | | 100 |
A. niger | | | | | | | | 2 | 1 | | 1 | | 4 | | | NB |
Other Aspergillus spp. | | | | | | | 2 | 3 | | 2 | | | 7 | | | NB |
Caspofungin (n = 38) | 0.06 | 0.125 | |
A. fumigatus complex | | | 3 | 8 | 5 | 1 | | | | | | | 17 | | | NB |
A. flavus | 1 | 3 | | 3 | | | 1 | | | | | | 8 | | | NB |
A. terreus | | | 2 | 1 | 1 | | 1 | | | | | | 5 | | | NB |
A. niger | | | 3 | 3 | | | | | | | | | 6 | | | NB |
Other Aspergillus spp. | | | | 1 | 1 | | | | | | | | 2 | | | NB |
Micafungin (n = 194) | 0.015 | 0.03 | |
A. fumigatus complex | 21 | 56 | 15 | | | | | | | | | | 92 | | | NB |
A. flavus | 5 | 16 | 7 | | | | 1 | | | | | | 29 | | | NB |
A. terreus | 6 | 15 | 7 | | | | | | | | | | 28 | | | NB |
A. niger | 7 | 6 | 12 | 2 | | | | | | | | | 27 | | | NB |
Other Aspergillus spp. | | 9 | 5 | 2 | 2 | | | | | | | | 18 | | | NB |
Anidulafungin (n = 194) | 0.015 | 0.03 | |
A. fumigatus complex | 1 | 75 | 16 | | | | | | | | | | 92 | | | NB |
A. flavus | 2 | 22 | 4 | | | | 1 | | | | | | 29 | | | NB |
A. terreus | | 17 | 11 | | | | | | | | | | 28 | | | NB |
A. niger | | 18 | 8 | 1 | | | | | | | | | 27 | | | NB |
Other Aspergillus spp. | | 5 | 7 | 4 | 2 | | | | | | | | 18 | | | NB |
NB, No Breakpoint |
Echinocandins demonstrated low MIC values overall, with micafungin and anidulafungin both having an MIC50/90 of 0.015/0.03 mg/L. Amphotericin B displayed poor activity against A. fumigatus complex with only 47% of isolates being susceptible according to the EUCAST clinical breakpoint. A total of 15 cryptic species underwent susceptibility testing (Table 2). High triazole MIC values were observed among cryptic species with a voriconazole MIC50/90 of 2/8 mg/L.
Table 2
Antifungal MIC values (mg/L) for cryptic Aspergillus species (n = 15)
Species | Year Collected | Voriconazole | Posaconazole | Itraconazole | Isavuconazole | Micafungin | Anidulafungin |
Aspergillus insuetus | 2018 | 4 | 1 | 0.5 | | 0.06 | 0.06 |
Aspergillus unguis | 2019 | 0.12 | 0.5 | 0.5 | | 0.03 | 0.03 |
Aspergillus ochraceus | 2019 | 0.5 | 0.5 | 0.5 | | 0.03 | 0.125 |
Aspergillus ustus | 2019 | 8 | > 8 | 1 | | 0.03 | 0.06 |
Aspergillus wisconsinensis | 2019 | 0.5 | 0.5 | 0.25 | | 0.015 | 0.015 |
Aspergillus fischeri | 2019 | 2 | 1 | 1 | | 0.015 | 0.015 |
Aspergillus lentulus | 2020 | 4 | 1 | 2 | | 0.015 | 0.015 |
Aspergillus vericolor | 2020 | 0.25 | 0.5 | 1 | | 0.015 | 0.015 |
Aspergillus calidoustus | 2020 | 8 | 2 | 1 | | 0.125 | 0.125 |
Aspergillus calidoustus | 2021 | 4 | 2 | 1 | 1 | 0.03 | 0.015 |
Aspergillus sydowii | 2021 | 1 | 0.5 | 0.5 | 0.5 | 0.015 | 0.015 |
Aspergillus oryzae | 2021 | 0.25 | 0.25 | 0.25 | 0.5 | 0.015 | 0.03 |
Aspergillus lentulus | 2021 | 8 | 0.5 | 1 | 4 | 0.015 | 0.03 |
Aspergillus ochraceus | 2021 | 1 | 1 | 1 | 1 | 0.06 | 0.06 |
Aspergillus calidoustus | 2021 | 4 | 2 | 1 | 1 | 0.015 | 0.03 |
Voriconazole and anidulafungin MIC values of isolates obtained between 2017 to 2021 (n = 150) were analysed according to year (Figs. 1 and 2). In 2021, there were a total of 6 isolates with a voriconazole MIC value of ≥ 2 mg/L; this compared to a total of 3, 2, 2, and 1 identified in 2020, 2019, 2018 and 2017, respectively. Anidulafungin MIC values did not appear to change during this 5-year period with > 95% of isolates obtained between 2017–2021 having an MIC value between 0.03 and 0.06 mg/L.
MIC distribution was not different between North and Southeast Queensland isolates (Fig. 3).