ABSTRACT:
Periodic surveillance of antifungal susceptibility among
Aspergillus
isolates is essential to guide effective treatment. This multicenter study analyzed 550 clinical
Aspergillus
isolates collected in Taiwan from 2021 to 2023, primarily from the respiratory tract (69.6%) and ear (12.9%). Calmodulin-based sequencing identified 24 species across six
Aspergillus
sections:
Flavi
(28.7%),
Fumigati
(28.5%),
Nigri
(21.6%),
Terrei
(15.8%),
Nidulantes
(5.1%), and
Circumdati
(0.2%). The major sections were represented by
Aspergillus fumigatus
(99.4%),
Aspergillus flavus
(91.8%), and
Aspergillus terreus
(100%), while section
Nigri
comprised nine species, with
Aspergillus welwitschiae
(57.1%) predominant. Using Clinical Laboratory Standards Institute (CLSI) M38-A3 protocols, reduced susceptibility to amphotericin B (MIC > 1 µg/mL) was observed in
A. flavus
(8.3%),
A. terreus
(22.7%), and section
Nidulantes
(32.1%). Acquired voriconazole resistance was found in 5.8% (9/156) of
A. fumigatus
isolates, including eight with
cyp51A
mutations (3 TR
34
/L98H, 4 TR
34
/L98H/S297T/F495I, and 1 TR
46
/Y121F/T289A). Voriconazole non-wild-type phenotypes were identified in 2.1% (3/158) of
A. flavus
isolates, including one carrying a novel P214L mutation (orthologous to
A. fumigatus
P216L). Members of the
Aspergillus niger
clade exhibited reduced susceptibility to itraconazole and isavuconazole. Anidulafungin, along with novel antifungals including orolofim, manogepix, and rezafungin, demonstrated broad activity across
Aspergillus
species, including those with intrinsic or acquired azole resistance. Ibrexafungerp also showed efficacy against azole-resistant
A. fumigatus
and
A. flavus
. In contrast, opelconazole exhibited limited activity against
A. flavus
, the
A. niger
clade,
Aspergillus sydowii
, and voriconazole-resistant
A. fumigatus
. These findings underscore the need for species-level identification, susceptibility testing of causative isolates, and continued surveillance to detect emerging resistance and support the use of novel non-azole antifungals for azole-resistant aspergillosis.
IMPORTANCE:
Timely and effective antifungal therapy is essential for aspergillosis. This multicenter surveillance study provides comprehensive insights into the species distribution and antifungal susceptibility of 550 clinical
Aspergillus
isolates in Taiwan, with intrinsic reduced susceptibility to amphotericin B, itraconazole, or isavuconazole noted in certain species. Regarding acquired resistance, a novel cyp51A mutation, P214L, was identified in an azole-resistant
Aspergillus flavus
, orthologous to
Aspergillus fumigatus
P216L. Recovery of azole-resistant
A. fumigatus
harboring TR34/L98H or TR46/Y121F/T289A mutations remains a concern and emphasizes the need for antifungal stewardship in the environment. Novel antifungals, including orolofim, manogepix, rezafungin, and ibrexafungerp, demonstrated broad activity across
Aspergillus
species, including resistant isolates. Nevertheless, the inhaled agent opelconazole exhibited limited activity against
A. flavus
regardless of voriconazole susceptibility and against other species showing reduced susceptibility to itraconazole. These findings highlight the importance of species-level identification, susceptibility testing, and continued surveillance and support the use of novel antifungals for aspergillosis.