Continuous Real-Time Motility Analysis of Acanthamoeba Reveals Sustained Movement in Absence of Nutrients

Acanthamoeba keratitis is a serious ocular infection which is challenging to treat and can lead to blindness. While this pathogen is ubiquitous and can contaminate contact lenses after contact with water, its habits remain elusive. Understanding this organism's natural behavior will better inform us on how Acanthamoeba colonize contact lens care systems. Acanthamoeba trophozoites were allowed to adhere to either a glass coverslip or non-nutrient agar (NNA) within a flow cell with nutrients (Escherichia coli or an axenic culture medium (AC6)) or without nutrients (Ringer's solution). Images were taken once every 24 s over 12 h and compiled, and videos were analyzed using ImageJ Trackmate software. Acanthamoeba maintained continuous movement for the entire 12 h period. ATCC 50370 had limited differences between conditions and surfaces throughout the experiment. Nutrient differences had a noticeable impact for ATCC 30461, where E. coli resulted in the highest total distance and speed during the early periods of the experiment but had the lowest total distance and speed by 12 h. The Ringer's and AC6 conditions were the most similar between strains, while Acanthamoeba in the E. coli and NNA conditions demonstrated significant differences between strains (p < 0.05). These results indicate that quantifiable visual tracking of Acanthamoeba may be a novel and robust method for identifying the movement of Acanthamoeba in relation to contact lens care products. The present study indicates that Acanthamoeba can undertake sustained movement for at least 12 h with and without nutrients, on both rough and smooth surfaces, and that different strains have divergent behavior.