Efficacy of the Culture Method Using a Flocked Swab and Brain-Heart Infusion Liquid Broth in Fungal Keratitis

Background: Fungal keratitis is a severe corneal infection that can lead to serious complications, including corneal perforation and endophthalmitis. Early identification of the causative fungi is essential for selecting appropriate antifungal therapy and improving clinical outcomes. Objective: This study aimed to evaluate the efficacy of a culture method using a flocked swab combined with brain-heart infusion (BHI) liquid medium, compared with the conventional cotton swab method, in patients with fungal keratitis. Methods: A retrospective review was performed on 15 patients clinically suspected of having fungal keratitis between March 2024 and July 2025. Each corneal lesion was sampled with a conventional cotton swab and a flocked swab before antifungal treatment. Conventional swabs were inoculated onto blood agar, chocolate agar, MacConkey agar, and Sabouraud dextrose agar plates, whereas flocked swabs were first incubated in BHI medium for 24 hours before being plated onto the same solid media. Results: The culture positivity rate was 20.0% (3/15) with the conventional method and 86.7% (13/15) with the flocked swab method (p = 0.00195). The median time to positivity was significantly shorter with the flocked swab method (96 hours; IQR 72-96) than with the conventional method (116 hours; IQR 107-117; p = 0.016). Three patients (20.0%) had mixed bacterial-fungal infections, two of which were detected only by the flocked swab method.