Instituto Valenciano de Microbiología

Masía El Romeral
Ctra. de Bétera a San Antonio Km. 0.3
46117 Bétera (Valencia)
Phone. 96 169 17 02
Fax 96 169 16 37
CIF B-96337217


Acanthamoeba spp. - amoebic keratitis (AK: Amebic keratitis) and granulomatous amoebic Encephalitis (GAE: Granulomatous Amebic Encephalitis): Microscopic examination, culture and molecular diagnosis (PCR).

Information 09/12/16.

Acanthamoeba spp. is a protozoan very ubicuitario free life in nature that can be found in habitats as diverse as natural freshwater, water taps, swimming pool water, earth (soil), sediments of oceans, air conditioning units, liquid maintenance contact lenses, dialysis units waters, ..., so are considered the most prevalent environmental protozoa. It has two life stages: trophozoites with active binary division develop pseudopods spinous hyaline, and cysts develop resistance when temperature conditions, pH and change dryness. They described 15 different genotypes (T1 to T15), become important when considering the sensitivity of molecular diagnostic tests. The most prevalent genotype in human infections is T4.

Several species of Acanthamoeba spp. We found causing severe cases of brain infection called granulomatous amoebic encephalitis (GAE: Granulomatous Amebic Encephalitis), a process that occurs in immunocompromised individuals with underlying conditions are difficult to diagnose, leading to a chronic course, which is often fatal and often diagnosed postmortem necropsy deceased patient but which have been currently described cases in which it has been able to make diagnosis with molecular methods applied to samples of cerebrospinal fluid before death, which can begin treatment. In addition, he is responsible for amoebic keratitis cases (AK: Amebic keratitis) that can cause blindness, affects young healthy individuals, particularly users of contact lenses.

The incidence of amoebic keratitis has increased over the past 30 years, calculated an incidence of 2-20 cases per million contact lens wearers, than in the US It is calculated corresponding to 10% of the population. Outbreaks have been associated with the use of batches of liquid solutions for maintenance of contact lenses were contaminated with Acanthamoeba spp. There are isolated cases of individuals who have undergone corneal trauma, washing contact lenses with tap water or other home preparations, or swimming or taking showers with wearing contact lenses. Amoebic keratitis is the acute, painful infection with nonspecific initial symptoms as a disproportionate eye pain, photophobia, redness, tearing, usually unilateral ocular involvement, but there are written cases of bilateral involvement. Patients suffering from corneal epithelium erosion irregularities and edema, accompanied by a radial infiltrate perineural, similar to that observed in Pseudomonas aeruginosa infections. Epithelial denudation and necrosis one stromal appears in subsequent stages also are frequent secondary bacterial infections, which complicates the diagnosis. Clinically it may be confused with Herpes simplex virus infection or fungal (fungal keratitis).

These processes appear to occur in several stages: adhesion of amoebae to host cells, cell invasion and tissue degradation. In cases of chronic (GAE) amoebic encephalitis amoebas would access the nervous system by hematogenous spread from a primary location in the lung or skin. In amoebic keratitis, amoebic environmental would be fixed to the eye tissue damaged corneal surface and invade the corneal stroma. Amoebas they segregate proteinases and serine proteases and have such binding ligands such as adhesion proteins ( "Laminin binding protein" and "Mannose Binding Protein). It has been shown in vitro that exposure of mannose amoebae trophozoites induces cytopathic release factors and lysis of corneal epithelial cells. This cytopathic activity can be inhibited by molecules that inhibit serine proteases, and also inhibiting fixation exogenous mannose.

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