RESUMO

The plasma membrane is essential in the pathogenicity of several microorganisms. However, to date, there are few studies related to the plasma membrane proteins in Naegleria fowleri; this amoeba produces a fatal disease called primary amoebic meningoencephalitis. In the present study, we analyzed the electrophoretic pattern of the membrane proteins of N. fowleri and compared it with the nonpathogenic N. lovaniensis and N. gruberi. We detected a 23-kDa protein (Nf23) present at a higher level in N. fowleri than in the nonpathogenic amoebae. The mass spectrometry analysis showed that the Nf23 protein has a sequence of 229 amino acids that corresponds to a membrane protein. The mRNA level of nf23 was overexpressed 4-fold and 40,000-fold in N. fowleri compared with N. lovaniensis and N. gruberi, respectively. Moreover, we found a 5-fold overexpression of nf23 in N. fowleri trophozoites recovered from mouse brains compared with trophozoites axenically cultivated. In addition, the cytopathic effect on Madin-Darby Canine Kidney cells coincubated with N. fowleri diminished in the presence of antibodies against Nf23; nevertheless, the nonpathogenic amoebae did not produce damage to the monolayer cells. These results suggest that the plasma membrane protein Nf23 is probably involved in the virulence of N. fowleri.

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RESUMO

A partir de 4 localidades donde se aislaron amebas del género Naegleria fowleri en Santiago de Cuba, se realizaron las técnicas necesarias para su adecuado estudio a través del microscopio electrónico de barrido. Con anterioridad, esas amebas fueron inoculadas en biomodelos experimentales (ratones), lo cual permitió determinar un nivel de patogenicidad diferente; y esto último, como es un aspecto controvertido en diversas teorías sobre sus causas (algunas analizadas aquí), entre las que se incluye la sustentada en la invaginación de su superficie (amebostomas o suctores), la autora de este trabajo se dio a la tarea de valorar la presencia (número y características) de los amebostomas o su ausencia a través del mencionado aparato, de donde se derivó que los ameboflagelados no patógenos apenas se diferenciaban de los que sí lo eran. Tal hallazgo pudo ser reafirmado cuando estos se compararon con 2 cepas reconocidas en el Instituto de Medicina Tropical de Checoslovaquia; por consiguiente, ese resultado descarta la citada causa en la patogenicidad de las amebas.

Taking into account 4 localities where amebas of the genus Naegleria fowleri were isolated in Santiago de Cuba, necessary techniques for their adequate study using the scanning electron microscope were performed. Previously, those amebas were inoculated in experimental biomodels (mice), which allowed to determine a different level of pathogenicity, a controversial issue in several theories about their causes (some discussed here), including that maintained in their surface invagination (amebostomas or suckers). Thus, the author of this work evaluated the presence (number and characteristics) or absence of amebostomas through such device, and it is concluded that pathogenic ameboflagellates were similar to those that were not. This finding could be confirmed when they were compared with 2 strains recognized in the Institute of Tropical Medicine of Czechoslovakia. Consequently, that result rules out the above cause in the pathogenesis of amebas.

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RESUMO

Naegleria fowleri is the etiologic agent of primary amoebic meningoencephalitis, a rapidly fatal parasitic disease of humans. The adherence of Naegleria trophozoites to the host cell is one of the most important steps in the establishment and invasiveness of this infectious disease. Currently, little is known about the surface molecules that may participate in the interaction of N. fowleri with their target cells. In the present study, we investigated the composition of glycoconjugates present on the surface of trophozoites of the pathogenic N. fowleri and the nonpathogenic Naegleria gruberi. With the use of biotinylated lectins in western blot and flow cytometric analysis, we showed that N. fowleri trophozoites present high levels of surface glycoconjugates that contain alpha-D-mannose, alpha-D-glucose, and terminal alpha-L-fucose residues. A significant difference in the expression of these glycoconjugates was observed between N. fowleri and the nonpathogenic N. gruberi. Furthermore, we suggest that glycoconjugates that contain D-mannose and L-fucose residues participate in the adhesion of N. fowleri and subsequent damage to MDCK cells.

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RESUMO

Acanthamoeba and Naegleria species are free-living amoebae (FLA) found in a large variety of natural habitats. The prevalence of such amoebae was determined from dust samples taken from public non-hospital internal environments with good standards of cleanliness from two campuses of the same University in the city of Santos (SP), Brazil, and where young and apparently healthy people circulate. The frequency of free-living amoebae in both campuseswas 39 percent and 17 percent respectively, with predominance of the genus Acanthamoeba. On the campus with a much larger number of circulating individuals, the observed frequency of free-living amoebae was 2.29 times larger (P< 0.00005). Two trophozoite forms of Naegleria fowleri, are the only species of this genus known to cause primary amoebian meningoencephalitis, a rare and non-opportunistic infection. We assume that the high frequency of these organisms in different internal locations represents some kind of public health risk.

Assuntos

RESUMO

Acanthamoeba and Naegleria species are free-living amoebae (FLA) found in a large variety of natural habitats. The prevalence of such amoebae was determined from dust samples taken from public non-hospital internal environments with good standards of cleanliness from two campuses of the same University in the city of Santos (SP), Brazil, and where young and apparently healthy people circulate. The frequency of free-living amoebae in both campuses was 39% and 17% respectively, with predominance of the genus Acanthamoeba. On the campus with a much larger number of circulating individuals, the observed frequency of free-living amoebae was 2.29 times larger (P< 0.00005). Two trophozoite forms of Naegleria fowleri, are the only species of this genus known to cause primary amoebian meningoencephalitis, a rare and non-opportunistic infection. We assume that the high frequency of these organisms in different internal locations represents some kind of public health risk.

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RESUMO

OBJECTIVE: To evaluate the occurrence of free-living amoebas of the genera Acanthamoeba and Naegleria is dust samples colleted in two hospitals. METHODS: One-hundred and thirty-two dust samples were collected in two hospitals in Brazil. Hospital collection sites were the following: intensive care unit, operation rooms, nursery, kitchen, emergency and infectious diseases isolation room. The isolation of the amoebas was performed in three culture media: non-nutrient agar inoculated with Escherichia coli, soy agar, and microculture in Giazzi-modified Pavlova's medium. The amoebas were identified according to morphological criteria. RESULTS: Amoebas of the genera Acanthamoeba and Naegleria were found in 45.5% of the samples, of which 41.6% were collected in the university hospital and 50% in the state hospital. Of all, 45.5% were positive for the genera Acanthamoeba and 3.8% for genera Naegleria. CONCLUSIONS: Potentially pathogenic free-living amoebas were seen in all sites of the two hospitals and Acanthamoeba was the most frequently isolated genera.

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RESUMO

Las pequeñas amebas de vida libre están ampliamente distribuidas en todo el mundo en continuo contacto con el hombre y animales; sus formas quísticas son capaces de sobrevivir en el suelo, aire y agua. Las infecciones causadas por las mismas han tomado en los últimos treinta años notable importancia médica ya que muchos casos fatales no fueron diagnosticados clínicamente ni por el laboratorio, debido al desconocimiento de la potencial capacidad patogénica de estas amebas. Hoy se sabe que la meningoencefalitis amebiana primaria (MAP) causada por Naegleria fowleri y la encefalitits amebiana granulomatosa (EAG) originada por especies de Acanthamoeba spp se han incrementado en el mundo tanto en sujetos sanos como en inmunocomprometidos, incluyendo muchos individuos con SIDA. El grupo más reciente de infecciones causadas por especies del género Acanthamoeba es la queratitis amebiana relacionada principalmente con la falta de cuidado en el mantenimiento de las lentes de contacto. La terapia de la queratitis es problemática debido a la presencia de quistes en los tejidos, y aunque se han informado algunas curas de pacientes, la terapéutica médica aún constituye un capítulo no resuelto

Assuntos

RESUMO

Las pequeñas amebas de vida libre están ampliamente distribuidas en todo el mundo en continuo contacto con el hombre y animales; sus formas quísticas son capaces de sobrevivir en el suelo, aire y agua. Las infecciones causadas por las mismas han tomado en los últimos treinta años notable importancia médica ya que muchos casos fatales no fueron diagnosticados clínicamente ni por el laboratorio, debido al desconocimiento de la potencial capacidad patogénica de estas amebas. Hoy se sabe que la meningoencefalitis amebiana primaria (MAP) causada por Naegleria fowleri y la encefalitits amebiana granulomatosa (EAG) originada por especies de Acanthamoeba spp se han incrementado en el mundo tanto en sujetos sanos como en inmunocomprometidos, incluyendo muchos individuos con SIDA. El grupo más reciente de infecciones causadas por especies del género Acanthamoeba es la queratitis amebiana relacionada principalmente con la falta de cuidado en el mantenimiento de las lentes de contacto. La terapia de la queratitis es problemática debido a la presencia de quistes en los tejidos, y aunque se han informado algunas curas de pacientes, la terapéutica médica aún constituye un capítulo no resuelto (AU)

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RESUMO

Amoebae were isolated from a natural thermal water source in Michoacán, Mexico, in September 1986. Two 500-ml samples were taken from pools with water at 45 degrees C and 46 degrees C and concentrated at 2,000 g for 15 min. The sediment was seeded on nonnutritive agar plates and incubated at 42 degrees C. The isolates were axenized in bactocasitone-serum medium. The identification of the isolates was based on their morphology, total protein and isoenzyme patterns by agarose isoelectric focusing, serology, fine structure, agglutination with Concanavalin A, sensitivity to trimethoprim, capacity to kill mice, and their cytopathic effect in Vero cells. The results showed several morphophysiological, biochemical and serological differences between the isolates and the type strain Aq/9/1/45D of Naegleria lovaniensis. These remarkable differences provide sufficient evidence to consider one of the isolates a new subspecies, and the other one a morphological variant of N. l. lovaniensis, which can be differentiated from other Naegleriae by their morphology, biochemistry, serology and physiology. The authors propose the name tarasca for the subspecies and purepecha for the morphological variant.

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