Acanthamoeba keratitis: a review of biology, pathophysiology and epidemiology

Abstract

Acanthamoeba keratitis is an infection caused by a unicellular protozoan of the genus Acanthamoeba that is universally widespread. Until now, most cases were reported in contact lens wearers, although it is also a reality for non‐wearers, mostly connected to corneal trauma. There is also a variation in incidence regarding the aetiology of the disease between developed and developing countries. Purpose This work is based on a literature review, and the main goal is to deepen the knowledge about Acanthamoeba keratitis, presenting the main risk factors and focusing on prevention actions for this type of corneal infection since the treatments are not always effective. It targets specialists in visual health to strengthen their knowledge in this area, as well as to allow them to better inform their patients about hygiene care, appropriate measures of disinfection and ways to minimise the risk of infection. At this stage, it is important to highlight the essential role that practitioners play in fitting, monitoring and following‐up patients to minimise the danger of infection. Recent findings It is well recognised that corneal trauma facilitates invasion by leaving an open door for microorganisms to penetrate the cornea. In addition to trauma, risk factors are mostly associated with patients’ behaviours, such as interaction of contact lenses with contaminated water in the shower, swimming pools and beaches, etc., lack of hygiene habits with contact lenses and respective cases, and the use of ineffective disinfecting solutions. The fact that a disinfecting solution is not completely effective against trophozoites and/or cysts, both forms of Acanthamoeba’s lifecycle, can cause the infection since one cyst alone leads to the emergence of a whole new population of Acanthamoeba. Summary It is necessary to reduce the risk of infection and, beyond the need to promote patient education to encourage correct CL hygiene behaviours, it should also be highlighted that there is an urgent need to enhance the efficacy of CL disinfection systems against all strains and both stages of Acanthamoeba through the creation of standardised methods. The ease of purchasing CLs without any supervision must also be considered a concern, and, in the near future, it is also important to develop and implement effective diagnostic methods and treatments for Acanthamoeba keratitis.

Acanthamoeba Keratitis, Pathology, Diagnosis and Treatment

“…If the infection presents itself in a person who does not wear contact lenses, it is often due to minor corneal trauma of the eye associated with infectious debris abrading the cornea. This is the common mechanism seen in developing countries where the prevalence of wearing contacts is not as high [19]. The prevalence of AK is also higher in men than women, most likely due to a less strict hygiene regimen or more outdoor activities.…”

“…At least eight of the genotypic classes (T2, T3, T4, T5, T6, T10, T11, and T15) have been shown to cause AK, with the most common causative genotype being T4 [17,18]. The most common infectious species are Acanthamoeba castellani and Acanthamoeba polyphaga, both from the T4 genotype [16,19]. The pathogen is transmitted through corneal contact with a contaminated substance.…”

Enfermedades por amebas de vida libre

“…Su incidencia varía entre países desarrollados y en vía de desarrollo, así como entre áreas geográficas; la incidencia suele ser menor en los países en desarrollo en comparación con los países desarrollados. En estos últimos, la mayoría de los casos están relacionados con el uso de lentes de contacto, de estos el 80 -85 % se relaciona a lentes de contacto blandos, aunque puede presentarse con lentes rígidos y ortoqueratológicos (12). N. fowleri se encuentra frecuentemente en suelos y aguas de ríos, lagos y gracias a sus propiedades termofílicas, se ha aislado en aguas termales con temperaturas de hasta 45°C.…”

Peganum harmala Extract Has Antiamoebic Activity to Acanthamoeba triangularis Trophozoites and Changes Expression of Autophagy-Related Genes

“…Acanthamoeba spp. can be transmitted to humans, and several routes of transmission, for example, ocular, nasal, and injured skin, are reported [ 3 , 4 , 5 ]. The clinical presentation in immunocompromised individuals may be more severe and may present with cutaneous lesions [ 6 ], chronic sinusitis [ 7 ], and granulomatous amebic encephalitis [ 8 ] depending on the site of infection.…”