(1) Background: Microbial keratitis is a serious eye infection that carries a significant risk of vision loss. Acanthamoeba spp. are known to cause keratitis and their bacterial endosymbionts can increase virulence and/or treatment resistance and thus significantly worsen the course of the disease. (2) Methods and Results: In a suspected case of Acanthamoeba keratitis, in addition to Acanthamoeba spp., an endosymbiont of acanthamoebae belonging to the taxonomic order of Holosporales was detected by chance in a bacterial 16S rDNA-based pan-PCR and subsequently classified as Candidatus Paracaedibacter symbiosus through an analysis of an enlarged 16S rDNA region. We used Oxford Nanopore Technology to evaluate the usefulness of whole-genome sequencing (WGS) as a one-step diagnostics method. Here, Acanthamoeba castellanii and the endosymbiont Candidatus Paracaedibacter symbiosus could be directly detected at the species level. No other microbes were identified in the specimen. (3) Conclusions: We recommend the introduction of WGS as a diagnostic approach for keratitis to replace the need for multiple species-specific qPCRs in future routine diagnostics and to enable an all-encompassing characterisation of the polymicrobial community in one step.

Mycotic keratitis is a rare but serious infection of the cornea that occurs particularly in wearers of contact lenses and in patients with systemic diseases, such as diabetes or immunosuppression. It is often caused by filamentous fungi such as Fusarium spp. and Aspergillus spp. or by yeasts, in particular Candida spp. The diagnosis of mycotic keratitis is challenging, as clinical signs are often non-specific. Diagnosis includes in vivo confocal microscopy, fungal cultures and histopathological examinations. Early and targeted diagnosis is crucial, in order to avoid serious complications. Treatment is based on the use of antimycotics such as natamycin and voriconazole. In refractory cases, early surgical intervention, usually by means of keratoplasty, is necessary. The aim of this article is to provide a comprehensive overview of the aetiology, diagnosis and treatment of mycotic keratitis and to provide clinical recommendations for the effective management of this challenging disease.

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This retrospective multicenter cohort study investigated the incidence, treatment, and prognostic impact of dysregulated intraocular pressure (DIOP; >24 mmHg requiring therapy) in patients with acanthamoeba keratitis (AK). Eighty-one eyes from 81 patients with confirmed AK were included; co-infections were excluded. DIOP and best corrected visual acuity (BCVA) were assessed at baseline, follow-up, and after penetrating keratoplasty (PKP). Overall, 28% of eyes were managed conservatively, 46% required one PKP, and 26% required two. DIOP occurred in 4% before AK, 11% after AK onset, and 10% after the first PKP. Eyes with DIOP prior to PKP had significantly worse final BCVA compared to those without DIOP (0.5 ± 0.7 vs. 1.8 ± 1.1 logMAR, p < 0.001) and required PKP more frequently (100% vs. 67%, p = 0.01). Time to correct diagnosis was significantly longer in the AK-associated DIOP group (64 ± 50 vs. 50 ± 68 days, p = 0.03). DIOP was also associated with higher rates of prior cortisone use and complications, including fixed dilated pupil, cataract, anterior synechiae, and anterior chamber irritation. Overall, DIOP represents a major complication in AK and is linked to poorer visual outcomes. Earlier therapy may help reduce DIOP and hence improve prognosis.