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. 2023 Jun;54(2):629-636.
doi: 10.1007/s42770-023-00964-w. Epub 2023 Apr 13.

Candida species causing fungal keratitis: molecular identification, antifungal susceptibility, biofilm formation, and clinical aspects

Fernanda M Bezerra  1 , Talita T Rocchetti  1 , Soraia L Lima  2 , Maria Cecília Z Yu  1 , Daniel A da Matta  2 , Ana Luisa Höfling-Lima  1 , Analy S A Melo  2 , Lauro A de Oliveira  3
Affiliations

Candida species causing fungal keratitis: molecular identification, antifungal susceptibility, biofilm formation, and clinical aspects

Fernanda M Bezerra et al. Braz J Microbiol. 2023 Jun.

Abstract

The study aimed to evaluate the clinical aspects, molecular identification, biofilm formation, and antifungal susceptibility profile of Candida species isolated from fungal keratitis. Thirteen Candida isolates from 13 patients diagnosed with Candida keratitis were retrieved and grown in pure culture. Species identification was performed by micromorphology analysis and ITS-rDNA sequencing. The broth microdilution method tested the minimum inhibitory concentration (MIC) of four antifungal drugs (fluconazole, amphotericin B, voriconazole, and anidulafungin). The biofilms were cultured and incubated with antifungal drugs for 24 h. The XTT reduction assay measured the biofilm activity. Biofilm MICs were calculated based on a 50% reduction in metabolic activity compared with the activity of the drug-free control. Among isolates, two were C. albicans, 10 were C. parapsilosis (sensu stricto), and one was C. orthopsilosis. All isolates were classified as susceptible or intermediate to all four antifungal drugs. Four isolates were very low biofilm producers (30%). Nine isolates were biofilm producers, and all biofilm samples were unsusceptible to all drugs tested. Previous ocular surgery was the most common underlying condition for fungal keratitis (84.6%), and C. parapsilosis was the most frequent Candida species (76.9%). Four patients (30.7%) needed keratoplasty, whereas two (15.3%) required evisceration. The biofilm formation ability of Candida isolates decreased antifungal susceptibility compared with planktonic cells. Despite in vitro antifungal susceptibility, almost half of the patients were unresponsive to clinical treatment and needed surgery.

Keywords: Antifungal agents; Biofilms; Candida; Cornea; Keratitis.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Biofilm antifungal susceptibility of all clinical isolates. (a) C. parapsilosis susceptibility to anidulafungin. (b) C. albicans susceptibility to anidulafungin. (c) C. parapsilosis susceptibility to amphotericin B. (d) C. albicans susceptibility to amphotericin B. (e) C. parapsilosis susceptibility to voriconazole. (f) C. albicans susceptibility to voriconazole
See this image and copyright information in PMC

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