Beauveria bassiana: an emerging pathogen of fungal keratitis

To investigate the clinical characteristics and treatment outcomes of fungal keratitis caused by Beauveria bassiana.

The clinical data of 11 consecutive patients with fungal keratitis caused by Beauveria bassiana in the Eye Hospital of Shandong First Medical University from January 2019 to May 2024 were retrospectively analyzed. The clinical features, etiological characteristics, treatments and outcomes were analyzed.

Most patients were farmers (10/11), with three cases caused by plant trauma and five cases having a history of corneal transplantation. Slit-lamp examination revealed that the keratopathy was characterized by dry ulcerative lesions, predominantly circular with relatively irregular borders. Several cases exhibited typical keratopathy signs of fungal keratitis, such as mycelial mat, pseudopodia and hypopyon. No significant immune ring structure was observed in any patients. Both the corneal scraping and in vivo confocal microscopy (IVCM) revealed branched and septate hyphae structures. Morphological and ITS sequencing identification was performed after isolation and cultivation. B. bassiana exhibited typical morphological characteristics: hyphae were branched, septate, transparent and slender; sympodial development of conidia was on a geniculate or zig-zag pattern; conidiogenous cells were flask-shaped, rachiform and sympodially proliferating, often aggregating into sporodochia or synnemata; conidia were hyaline and globose or ovoid in shape. B. bassiana had a relatively high susceptibility to the majority of antifungal agents in vitro. One patient was treated with medical therapy alone. The five patients with a history of corneal transplantation underwent penetrating keratoplasty (PKP). The two patients with ulcer depth < 1/2 corneal thickness and ulcer diameter ≤ 3 mm underwent corneal ulcer debridement combined with medical treatment. The three patients with ulcer depth exceeding 1/2 corneal thickness underwent PKP. Following treatment, no patient experienced recurrence during the follow-up period.

Plant trauma, immunosuppression and involvement in agricultural production have been identified as significant risk factors for B. bassiana keratitis. Although the strains exhibited low minimal inhibitory concentrations (MICs) to most antifungal agents in vitro, early diagnosis and treatment remain crucial.