Clinical presentation, genotypic diversity, and intracellular bacteria in Acanthamoeba keratitis patients treated at a referral eye hospital in Sydney, Australia

Objectives: Acanthamoeba keratitis (AK) is an emerging corneal infection. This study evaluated the prevalence of AK, assessed circulating Acanthamoeba genotypes, and identified potential sources of infection. Methods: A prospective case series study was conducted at the Sydney Eye Hospital, Australia, from June 2021 and October 2022. Corneal swabs from AK patients were collected for culture, and their domestic water samples were also analyzed. Cyst morphology, polymerase chain reaction, and Sanger sequencing were performed to confirm the Acanthamoeba isolates. Results: A total of 21 AK patients were recruited in this study (41 ± 12.3 years). Six (28.6%) corneal and four (44.4%) water samples tested positive for Acanthamoeba genotype T4. One corneal and one water isolate harbored intracellular bacteria, with the water isolate containing Pseudomonas aeruginosa. Eight patients were contact lens wearers. Eye pain was the primary symptom (66.7%), followed by red eye. The median duration of symptoms was 24.5 days (interquartile range: 13–95 days). Polyhexamethylene biguanide was the main therapy, followed by chlorhexidine. The median treatment duration was 12 weeks (interquartile range: 8–26 weeks). Conclusions: In Sydney, the prevalent genotype of Acanthamoeba among AK patients and tap water was T4. This study suggests a higher annual incidence of AK than previously reported.