Eye Infections Caused by Filamentous Fungi: Spectrum and Antifungal Susceptibility of the Prevailing Agents in Germany

Abstract

Fungal eye infections can lead to loss of vision and blindness. The disease is most prevalent in the tropics, although case numbers in moderate climates are increasing as well. This study aimed to determine the dominating filamentous fungi causing eye infections in Germany and their antifungal susceptibility profiles in order to improve treatment, including cases with unidentified pathogenic fungi. As such, we studied all filamentous fungi isolated from the eye or associated materials that were sent to the NRZMyk between 2014 and 2020. All strains were molecularly identified and antifungal susceptibility testing according to the EUCAST protocol was performed for common species. In total, 242 strains of 66 species were received. Fusarium was the dominating genus, followed by Aspergillus, Purpureocillium, Alternaria, and Scedosporium. The most prevalent species in eye samples were Fusarium petroliphilum, F. keratoplasticum, and F. solani of the Fusarium solani species complex. The spectrum of species comprises less susceptible taxa for amphotericin B, natamycin, and azoles, including voriconazole. Natamycin is effective for most species but not for Aspergillus flavus or Purpureocillium spp. Some strains of F. solani show MICs higher than 16 mg/L. Our data underline the importance of species identification for correct treatment.

Malignant Keratitis Caused by a Highly-Resistant Strain of Fusarium Tonkinense from the Fusarium Solani Complex

“…Species of the Fusarium solani species complex are the prevailing agents of Fusarium keratitis [8,21,22]. In Germany, the most common species isolated from keratomycoses are F. petroliphilum, F. keratoplasticum and F. solani [8].…”

“…Based on the colony morphology on Sabouraud agar (Figure 9a,b) and the micromorphological characteristics (Figure 10a,b), the fungus was classified as Fusarium spp. Molecular identification via amplification/sequencing of the ITS (internal transcribed spacer) region and the translation elongation factor 1α (TEF) were performed as described previously [8]. The ITS and TEF sequences unambiguously identified the strain as F. tonkinense: the ITS sequence (GenBank accession number MZ707714) was 100% identical with that of the ex-type strain of F. tonkinense CBS 115.40 (GenBank accession number: NR_170733).…”

“…In addition, Fusarium spp. are a leading cause of fungal eye infections which have shown an increasing incidence in recent years [6,8]. Even keratitis outbreaks have been reported associated with the use of a certain brand of lens solutions [9,10].…”

“…Even keratitis outbreaks have been reported associated with the use of a certain brand of lens solutions [9,10]. In contrast to bacterial forms of keratitis, the course of Fusarium keratitis is usually more progressive [6,8] and the consequences generally more serious [8,11,12], not least because the antifungal therapy is less efficient, since these fungi are a priori resistant to many types of antimycotics [8,11,13]. There is evidence that these pathogens possess certain virulence factors that enable destruction of tissue barriers and progression [6,14].…”

“…There is evidence that these pathogens possess certain virulence factors that enable destruction of tissue barriers and progression [6,14]. Fungi from the F. solani species complex such as F. falciforme, F. keratoplasticum, F. petroliphilum are particularly common in cases of Fusarium keratitis besides F. oxysporum, F. proliferatum (out of the F. fukikuroi complex) and others [6,8,11].…”