Free-living amoebae (FLA) are protozoa widely distributed in the environment, found in a great diversity of terrestrial biomes. Some genera of FLA are linked to human infections. The genus Acanthamoeba is currently classified into 23 genotypes (T1-T23), and of these some (T1, T2, T4, T5, T10, T12, and T18) are known to be capable of causing granulomatous amoebic encephalitis (GAE) mainly in immunocompromised patients while other genotypes (T2, T3, T4, T5, T6, T10, T11, T12, and T15) cause Acanthamoeba keratitis mainly in otherwise healthy patients. Meanwhile, Naegleria fowleri is the causative agent of an acute infection called primary amoebic meningoencephalitis (PAM), while Balamuthia mandrillaris, like some Acanthamoeba genotypes, causes GAE, differing from the latter in the description of numerous cases in patients immunocompetent. Finally, other FLA related to the pathologies mentioned above have been reported; Sappinia sp. is responsible for one case of amoebic encephalitis; Vermamoeba vermiformis has been found in cases of ocular damage, and its extraordinary capacity as endocytobiont for microorganisms of public health importance such as Legionella pneumophila, Bacillus anthracis, and Pseudomonas aeruginosa, among others. This review addressed issues related to epidemiology, updating their geographic distribution and cases reported in recent years for pathogenic FLA.

Free-living amoebae (FLA) are protozoa widely distributed in the environment, found in a great diversity of terrestrial biomes. However, few genera of FLA are linked to human infections. Within these genera, Acanthamoeba spp., classified by genotypes (T1-T23), being T1, T2, T4, T5, T10, T12, and T18 as capable of causing granulomatous amoebic encephalitis (GAE) in immunocompromised patients mostly and Acanthamoeba keratitis related to genotypes T2, T3, T4, T5, T6, T10, T11, T12 and T15 in apparently healthy patients. Meanwhile, Naegleria fowleri is the causative agent of an acute infection called primary amoebic meningoencephalitis (PAM), while Balamuthia mandrillaris, like some Acanthamoeba genotypes, causes GAE, differing from the latter in the description of numerous cases in patients immunocompetent. Finally, other FLA related to the pathologies mentioned above have been reported; Sappinia pedata is responsible for one case of amoebic encephalitis; Vermamoeba vermiformis has been found in cases of ocular damage, and its extraordinary capacity as endo-cytobiont for microorganisms of public health importance such as Legionella pneumophila, Bacillus anthracis, Pseudomonas aeruginosa, among others. In this review, issues related to the epidemiology of each one are addressed, updating their geographic distribution and cases reported in recent years for pathogenic FLA.

Realizamos muestreos mensuales para determinar la concentración de Naegleria fowleri en cuatro cuerpos de agua naturales del Valle del Yaqui, Sonora, México. Medimos la temperatura, el oxígeno disuelto y el pH del agua. Las muestras de agua fueron agitadas y procesadas para determinar la concentración por el método del número más probable (NMP), y sembradas en placas de agar no nutritivo con Escherichia coli. Cada amiba detectada se aisló en una nueva placa para continuar con la identificación. Se usaron tablas de MPN para el conteo de amibas, y la identidad de los géneros Naegleria y N. fowleri fue usando cebadores específicos y PCR de punto final. Identificamos N. fowleri en los cuatro cuerpos de agua durante las temporadas de verano y otoño, con 70 MPN L-1 como la concentración más alta. Seleccionamos siete cepas de N. fowleri para secuenciación y genotipado; todos pertenecían al tipo 2. A través de los resultados podemos afirmar que debido a las variaciones que se dan en la dinámica poblacional y la diversidad ecológica de los sitios estudiados, diferentes factores bióticos o abióticos, además de la temperatura, oxígeno disuelto, y el pH, influyen en la presencia o ausencia de esta especie. Esto dificulta la predicción de su presencia en ambientes acuáticos naturales con poblaciones relativamente bajas.