Abstract
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KEYWORDS: cornea, keratitis, scraping
ANSWER TO PHOTO QUIZ
The organism was identified as Scolecobasidium sp. (also reported as Ochroconis sp. [1]). The lactophenol cotton blue staining showed olivaceous conidiophores arising from aerial hyphae and sympodial, denticular conidiogenous cells. Conidia are smooth, subhyaline, and restricted at the septum, having a peanut-like shape, with the two cells being symmetrical or with the distal cell being smaller and more elongated while the proximal cell presents a small denticle (2). Sequencing of 28S rRNA showed 100% sequence identity with reference NCBI sequences of Scolecobasidium musae strain CBS 124.65 (GenBank accession no. KT272085.1).
Scolecobasidium includes different ubiquitous moulds, among which are S. musae and other species previously classified as Ochroconis spp. These fungi are characterized by slow or moderate growth, brownish colonies, and septate cylindrical conidia that are either smooth or rough walled. Even though it is mainly considered a nonpathogenic mold, with most species growing at 25 to 30°C, Scolecobasidium has been associated with respiratory, skin, and systemic infection (3). In particular, due to its presence in humid and warm environments, including sinks and bath edges, a case of a subcutaneous infection by S. musae in an immunocompetent host has been reported (4). Our patient presented multiple risk factors for development of infectious keratitis: an epithelial defect, contact lens use, and inflammatory dry eye secondary to cicatricial conjunctivitis. The actual source of infection is unknown but may be related to contamination with nonsterile water sources, inadvertent trauma, eyelid involvement, or possibly contamination of eye drop bottles. Only one other case of fungal keratitis by Ochroconis sp. has been reported so far (5), possibly because of frequent misdiagnosed infections and taxonomic rearrangement.
Since morphology cannot differentiate between Scolecobasidium sp. and Ochroconis sp., laboratories should refer to morphological features that could help start empirical therapy. Currently no particular resistance to antifungal drugs has been reported for discrete species. Susceptibility testing, however, should be performed in reference laboratories to help the management of local therapy (6). In our case, despite low MICs of triazoles and amphotericin B, the infiltrate worsened and the patient was scheduled for emergency therapeutic penetrating keratoplasty with intracameral irrigation of voriconazole. Histopathology of the corneal button revealed superficial involvement without penetration of hyphae in the deep layers. Culture-based assay of the corneal explant confirmed the presence of the same species. After 2 months of follow-up, the patient had a clear corneal graft in the right eye without signs of recurrence of fungal keratitis.
Footnotes
See https://doi.org/10.1128/JCM.00074-23 for photo quiz case presentation.
Contributor Information
N. Mancini, Email: nicasio.mancini@uninsubria.it.
Erik Munson, Marquette University.
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