Biology and pathogenesis of Acanthamoeba

Acanthamoeba is an opportunistic protist that is ubiquitously distributed in the environment. Acanthamoeba has two stages in its life cycle, an active trophozoite stage that exhibits vegetative growth and a dormant cyst stage with minimal metabolic activity. It is a causative agent of cutaneous lesions and sinus infections, vision-threatening keratitis and a rare but fatal encephalitis, known as granulomatous amoebic encephalitis [1-3]. The ability of Acanthamoeba to (i) produce serious human infections associated with a rise in the number of immunocompromised patients and contact lens wearers, (ii) their potential role in ecosystems, (iii) ability to act as a host/reservoir for microbial pathogens, and (iv) model organism for motility studies has led to a significant interest in this organism over the years (Figure 1). Furthermore, Acanthamoeba may have veterinary significance as demonstrated by the presence of amoebae in diseased or dead cows, dogs, pigs, rabbits, pigeons, sheep, reptiles, fish, turkeys, keel-billed toucan, Ramphastos sulfuratus, horses [4-6].Amoebae are among the earliest eukaryotes that have been studied since the discovery of the early microscope, e.g., Amoeba proteus, or closely related Chaos that is a genus of giant amoebae, varying from 1-5 mm in length. Based on rRNA sequences, it is estimated that amoebae have diverged from the main line of eukaryotic descent, sometimes between the divergence of yeast (~1.2 × 109 years ago) and the divergence of plants and animals (~1 × 109 years ago). Over the past several decades, these organisms have gained increasing attention due to their diverse roles in the ecosystem and in particular, their role in causing serious and sometimes fatal human infections (Figure 2).？ Entamoeba histolytica is a parasitic protist that was discovered in 1873 from a patient suffering from bloody dysentery [7,8] and named E. histolytica in 1903 [9,10]. This species was separated into one pathogenic (E. histolytica) and anot