Acanthamoeba keratitis: Molecular typing of Acanthamoeba species directly from ocular tissue

This report explores the molecular profiling of Acanthamoeba spp. from individuals in the UK suffering from a debilitating, sight-threatening disease of the cornea known as Acanthamoeba keratitis (AK). Seventy ocular samples from individuals undergoing investigations for AK were sent to the Scottish Microbiology Reference Laboratories (SMiRL), Glasgow during 2017-2019, and subjected to DNA extraction followed by in-depth molecular typing using a nested PCR/bi-directional sequencing approach. Of the 70 samples tested, 40 were PCR-positive. Of these, 32 were successfully sequenced and assigned to two of 23 existing genotypes termed T1 to T23. Molecular profiling of the 32 samples highlighted two genotypes, namely T3 (n = 3) and T4 (n = 29). For those 29 samples identified as the T4 genotype, a sub-genotype (T4A-T4H) was recorded: T4A (n = 18); T4B (n = 5); T4C (n = 1); T4E (n = 4); and T4F (n = 1). This study highlights that the T4 genotype and T4A subtype are the predominant molecular variants to cause ocular disease in the UK. Gaining in-depth information on the molecular profiling of Acanthamoeba spp. is essential to increase our understanding of the source(s) of infection, transmission pathways, and potential associations with clinical outcomes for this rare, yet potentially debilitating ocular disease.