ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Infectious Agents and Disease
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1632354
Clinical Characterization and Etiological Insights: A Small Cohort Study of Pulmonary Infections Caused by Microascus spp. in Critically Ill Patients
Provisionally accepted
- The Fourth Affiliated Hospital of Soochow University, Suzhou, China
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Microascus spp., globally distributed fungi, are increasingly recognized as causative agents of rare and refractory invasive infections in immunocompromised populations, with approximately 50 cases reported worldwide. This study aimed to characterize the epidemiological features, antifungal resistance profiles, and identification strategies for Microascus-associated pulmonary infections. Ten Microascus isolates were collected from respiratory specimens of patients with pulmonary infections (2021-2024). Clinical characteristics were analyzed, and antifungal susceptibility testing (AFST) was performed following CLSI M38-A3 guidelines. Taxonomic identification integrated MALDI-TOF mass spectrometry, and multilocus phylogenetic analysis (ITS/EF-1α/TUB). Nine of ten cases occurred in hematopoietic stem cell transplant (HSCT) recipients, with concurrent infections by cytomegalovirus (7/9), Pseudomonas aeruginosa (5/9), Corynebacterium striatum (5/9), or Aspergillus spp (5/9). Three patients succumbed to refractory infections. Morphologically, colonies exhibited olive-to-black concentric rings, floccose hyphae with dark granules, and basally swollen conidiophores producing oval or pear-shaped conidia in chains. Nine isolates were M. gracilis, and one was M. cirrosus. All strains demonstrated resistance to fluconazole, amphotericin B, and flucytosine (MIC >64 μg/mL) but high sensitivity to terbinafine (MIC ≤0.125 μg/mL). MALDI-TOF accurately identified M. gracilis (100%), while M. cirrosus required sequencing for confirmation. Multilocus sequence typing revealed a monophyletic cluster among M. gracilis isolates. Microascus spp. represent underdiagnosed pathogens in HSCT-associated fungal pneumonia, often complicated by polymicrobial infections. Terbinafine demonstrates promising in vitro efficacy against multidrug-resistant strains. A multimodal diagnostic approach combining morphology, MALDI-TOF, and sequencing is essential for species-level identification.
Keywords: Microascus spp, Hematopoietic Stem Cell Transplantation, Antifungal susceptibility testing, MALDI-TOF, Multilocus Sequence Typing
Received: 22 May 2025; Accepted: 18 Sep 2025.
Copyright: © 2025 Zhang, Cheng, Bi, Zhu, Zhou, Chen and Han. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Qing-Zhen Han, gyhqz2021@163.com
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