Infections with free-living amebae.

Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri are mitochondria-bearing, free-living eukaryotic amebae that have been known to cause infections of the central nervous system (CNS) of humans and other animals. Several species of Acanthamoeba belonging to several different genotypes cause an insidious and chronic disease, granulomatous amebic encephalitis (GAE), principally in immunocompromised hosts including persons infected with HIV/AIDS. Acanthamoeba spp., belonging to mostly group 2, also cause infection of the human cornea, Acanthamoeba keratitis. Balamuthia mandrillaris causes GAE in both immunocompromised and immunocompetent hosts mostly in the very young or very old individuals. Both Acanthamoeba spp. and B. mandrillaris also cause a disseminated disease including the lungs, skin, kidneys, and uterus. Naegleria fowleri, on the other hand, causes an acute and fulminating, necrotizing infection of the CNS called primary amebic meningoencephalitis (PAM) in children and young adults with a history of recent exposure to warm fresh water. Additionally, another free-living ameba Sappinia pedata, previously described as S. diploidea, also has caused a single case of amebic meningoencephalitis. In this review the biology of these amebae, clinical manifestations, molecular and immunological diagnosis, and epidemiological features associated with GAE and PAM are discussed.

The genus Sappinia: history, phylogeny and medical relevance.

The genus Sappinia with the single species Sappinia pedata was established for an amoeba with two nuclei and pedicellate "cysts" by Dangeard in 1896. In 1912, Alexeieff transferred an also double nucleated, but apparently sexually reproducing amoeba to this genus as Sappinia diploidea, that had been described as Amoeba diploidea by Hartmann and Nägler in 1908. As the original isolates were lost, Michel and colleagues established a neotype for S. diploidea in 2006 and Brown and colleagues established a neotype for S. pedata in 2007. Molecular analyses have corroborated the differentiation between S. pedata and S. diploidea, however, the genus splits into more than two well separated clusters. Altogether, the genus Sappinia is now classified as a member of the Thecamoebidae and, moreover, as potentially pathogenic. In 2001, Gelman and colleagues reported a case of severe encephalitis in a non-immunocompromised young man caused by Sappinia.

Infecciones por amebas de vida libre. Comentarios históricos, taxonomía y nomenclatura, protozoología y cuadros anátomo-clínicos / Infections caused by free-living amebas: historical commentaries, taxonomy and nomenclature, protozoology and clinicopathologic features

Infections caused by free-living amebae constitute one of emergent opportunistic infections with greatest medical interest. Although infrequently, they have been described in almost all world, its diagnosis depends on a high index of suspicion, especially in morpho-pathologic and laboratory studies. Exciting historical features of infections due to free-living amebae, its taxonomy and the present nomenclature are briefly reviewed. An analysis of the protozoology of the most frequent agents is done and, based on the author's own experience and the published one, already established anatomo-clinical entities are described: the primary amebic meningoencephalitis, granulomatous amebic encephalitis, Acanthamoeba keratitis, cutaneous acanthamoebiasis, disseminated infection and other rare isolated locations.

The discovery of nephrouroameba: was it real or not?

In 1938 Procaccini showed scientific interest in a new kind of ameba, and called it "nephrouroameba" from which the disease "nephrouroamebiasis" is derived. He wrote a paper titled "La Nefrouroamoebiasi" thus describing its history, the biopathogenetic evolutionary cycle of the protozoon, its therapeutic, epidemiological, anatomo-biological, diagnostic, cultural, biological and morphological features. Between 1934 and 1939, Procaccini had the opportunity to follow many patients belonging to a group of Italian soldiers serving in the Eastern Italian Army in Ethiopia. At that time he was responsible for the biopathological laboratory. After a short preclinical stage of fatigue, patients suffering from nephrouroamebiasis showed a nephrotic syndrome with gross hematuria. The symptoms ceased within a few days but residual microhematuria, albuminuria and urine casts persisted for many months. After microscopic observation, he reproduced some protozoons and classified them as a kind of ameba. Critical analysis of his report leads to the morphological identification of Trichomonas, thus excluding his classification as nephrouroamebas.

Amibiasis en el hombre: una perspectiva biológica y social

Desde el punto de vista epidemiológico, la infección por Entamoeba histolytica no constituye un problema mayor, pues rara vez es responsable de la muerte del huésped o implica lesión incapacitante grave, especialmente si se compara con enfermedades parasitarias de mayor impacto sobre las tasas de morbilidad y mortalidd a nivel mundial como la malaria y la equistosomiasis. Sin embargo, la amibiasis causa morbilidad en millones de personas por otro lado completamente saludables y, en ocasiones, de no llevarse a cabo un tratamiento adecuado, da lugar a complicaciones potencialmente fatales (como absceso hepático, absceso cerebral, peritonitis, amibiasis mediastino-pericárdica, amibiasis pleuropulmonar). En el presente artículo revisaremos la clasificación, morfología y ciclo biológico de Entamoeba histolytica, la epidemiología de la infección amibiana y la interrelación huésped-parásito (con énfasis en las características de la amiba que la hacen patógena para el hombre y en los mecanismos de defensa del huésped, indispensables ambos para comprender la patogenia de la enfermedad). En el próximo número pasaremos revista a los diversos cuadros clínicos a que da lugar la infección por amibas, los diferentes medios de diagnóstico empleados en su detección y las medidas indispensables para el tratamiento individualizado de los pacientes y para el control de su difusión en la población

Entamoeba histolytica and Homo sapiens.

Blind acceptance of the dicta of the great has led to much confusion as to the relationship between amoeba and man. A review of the mistakes of the past may lead to a better appreciation of the present, and higher hopes for the future. An hypothesis is presented.