Species identification and antifungal susceptibility testing of Aspergillus strains isolated from patients with otomycosis in northern China

Abstract

Background/purpose: There are limited studies on species distribution and susceptibility profiles of Aspergillus strains isolated from patients with otomycosis in China.

Methods: A total of 69 confirmed Aspergillus species isolates were obtained from ear swabs of patients diagnosed with otomycosis from 2017 to 2018 in northern China. Identification of these Aspergillus isolates at the species level was performed using conventional morphological methods and MALDI-TOF MS in combination with molecular sequencing, and in vitro susceptibility to nine antifungal agents was evaluated using the Sensititre YeastOne system.

Results: The Aspergillus section Nigri had the greatest distribution of Aspergillus isolates. A. welwitschiae (n = 25) was the most predominant isolate in section Nigri, followed by A. tubingensis (n = 12) and A. niger (n = 11). Other Aspergillus species were also isolated, including A. terreus (n = 11), A. flavus/A. oryzae (n = 8), and A. fumigatus (n = 2). Amphotericin B, posaconazole, and echinocandins were highly in vitro active against all the isolates tested. 2.9% (2/69) of the isolates were resistant to azoles in our study, including one A. niger isolate with a high MIC value for itraconazole (ITR) (16 mg/L) and one A. tubingensis isolate cross-resistant to both voriconazole (VOR) (MIC >8 mg/L) and ITR (MIC >16 mg/L). One A. welwitschiae and one A. niger isolate both had increased MIC values of 4 mg/L against VOR.

Conclusions: A. welwitschiae was the most prevalent Aspergillus species isolated from patients with otomycosis. Our findings also indicated that the azole-resistant Aspergillus section Nigri should be utilized to guide clinical medication for Otomycosis.

Keywords: Antifungal susceptibility testing; Aspergillus welwitschiae; Northern China; Otomycosis; Species identification.