Clinical profiling, antifungal drug susceptibility, and biofilm formation ability in pulmonary mucormycosis

Pulmonary mucormycosis (PM), a life-threatening infection caused by Mucorales, exhibits high mortality. Comprehensive data integrating clinical profiling, antifungal susceptibility, and biofilm formation ability are limited. This retrospective study characterized 26 adult PM patients at a Beijing tertiary-care hospital. Data on demographics, underlying diseases, co-infections, and outcomes were collected. Clinical Mucorales isolates underwent molecular identification via 18 S rRNA gene sequencing and phylogenetic analysis. In vitro susceptibility against nine antifungals (amphotericin B, fluconazole, voriconazole, itraconazole, posaconazole, caspofungin, micafungin, anidulafungin, 5-flucytosine) was determined using Sensititre YeastOne YO10 panels. Biofilm biomass was assessed (24 h, 48 h, 72 h) via the crystal violet staining assay. Patients were predominantly older males (median age 66 years, 65.4% male) with high comorbidity burden (92.3%). All-cause in-hospital mortality was 38.5%. Strikingly, 80.8% had co-infections. Temporal analysis revealed that viral (77.8%) and fungal (62.5%) co-infections often preceded the detection of Mucorales. Molecular identification confirmed Rhizopus spp. (54%) predominated, followed by Rhizomucor spp. (19%), Mucor spp. (19%), and Lichtheimia spp. (8%). Antifungal testing showed amphotericin B possessed the most consistent activity (MIC₅₀/MIC₉₀: 1/2 µg/mL). Posaconazole was the most potent azole (MIC₅₀/MIC₉₀: 0.25/1 µg/mL), but profound genus-level heterogeneity was observed. Biofilm assessment at the 48-h peak revealed biofilm formation in 84.6% (22/26) of isolates. This study highlights the high prevalence of antecedent viral/fungal co-infections preceding Mucorales detection and significant mortality, despite in vitro susceptibility to amphotericin B/posaconazol. In addition, most of the strains demonstrated biofilm formation ability, with evident genus-level heterogeneity. These findings emphasize the imperative of species-level identification and consideration of genus-specific traits to guide effective management of this life-threatening infection.