First Report of Human Infection Caused by Aspergillus steynii and Analysis of Its Whole-Genome Characteristics.

The incidence of infections caused by rare pathogens has increased in recent years. This necessitates the development of effective diagnostic and therapeutic approaches. In this study, we report the first documented case of Aspergillus steynii-induced pulmonary infection in humans. We evaluated the morphological and molecular characteristics of this fungus to elucidate its role in human infections. A 47-year-old woman with immunosuppression after bone marrow transplantation developed symptoms of pulmonary infection. The pathogen was identified as A. steynii through culture techniques, microscopy, mass spectrometry, multigene molecular identification, and whole-genome sequencing. Antifungal susceptibility testing was performed, and comparative genomic analysis was conducted to assess the phylogenetic relationship and genomic characteristics of A. steynii and other pathogenic Aspergillus species. Genomic analysis revealed a high degree of similarity with other pathogenic Aspergillus species. Furthermore, we identified 470 unique gene families primarily associated with ABC transporter pathways linked to multidrug resistance. The strain was sensitive to triazoles and echinocandins but exhibited elevated minimum inhibitory concentrations (MICs) for amphotericin B, flucytosine, and fluconazole. In addition, multiple potential drug resistance genes were identified, indicating the potential for multidrug resistance. The emergence of A. steynii in humans poses new clinical challenges and risks, including cross-species transmission and multidrug resistance. The potential for A. steynii infections, particularly in immunosuppressed patients, highlights the importance of early diagnosis and timely intervention to reduce the risk of misdiagnosis or delayed treatment. Thus, our findings have the potential to improve the clinical and differential diagnosis of this infection and facilitate the development of effective therapeutic approaches.