title: Acanthamoeba culbertsoni: Electron-Dense Granules in a Highly Virulent Clinical Isolate.
abstract: The virulence of various amoebic parasites has been correlated with the presence of electron-dense granules (EDGs) in the cytoplasm of trophozoites. Here, we report the finding by transmission electron microscopy of a large number of EDGs in a recent culture of Acanthamoeba culbertsoni, isolated from a severe case of human keratitis. When this isolate was maintained in culture for 6 mo, the granules almost disappeared. However, after induction of mice brain lesions with the long-term cultured isolate, recovered amoebas had abundant EDGs. Trophozoites of the original isolate, or those recovered from experimental lesions, secreted EDGs into the medium when incubated with MDCK cells. To analyze a possible cytotoxic effect the conditioned medium was incubated with MDCK monolayers. After 5 h, the media containing EDGs produced opening of the tight junctions; at 24 h, cell viability was compromised, and at 48 h most of the cells were detached from the monolayer. In contrast, trophozoites in long-term cultures did not release EDGs to the medium during incubation with MDCK cells, and the corresponding conditioned medium did not have any effect on MDCK monolayers. Our observations further support the hypothesis that EDGs play a role in the cytopathogenic mechanisms of A. culbertsoni.
authors.affiliation: Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Mexico City, 07360, Mexico. bchavez@cinvestav.mx.
authors.forename: Bibiana
authors.initials: B
authors.lastname: Chávez-Munguía
authors.affiliation: Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Mexico City, 07360, Mexico.
authors.forename: Lizbeth
authors.initials: L
authors.lastname: Salazar-Villatoro
authors.affiliation: School of Superior Studies Iztacala, National Autonomous University of Mexico, Mexico City, 54090, Mexico.
authors.forename: Maritza
authors.initials: M
authors.lastname: Omaña-Molina
authors.affiliation: Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Mexico City, 07360, Mexico.
authors.forename: Martha
authors.initials: M
authors.lastname: Espinosa-Cantellano
authors.affiliation: School of Superior Studies Iztacala, National Autonomous University of Mexico, Mexico City, 54090, Mexico.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ramírez-Flores
authors.affiliation: University Institute of Tropical Diseases and Public Health of the Canary Islands, University of La Laguna, Canary Islands, 38203, Spain.
authors.forename: Jacob
authors.initials: J
authors.lastname: Lorenzo-Morales
authors.affiliation: Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Mexico City, 07360, Mexico.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Martínez-Palomo
mesh_terms: D000048:Acanthamoeba / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity* / Q000648:ultrastructure*; D000562:Amebiasis / Q000469:parasitology*; D000818:Animals; D006801:Humans; D007634:Keratitis / Q000469:parasitology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission; D053058:Trophozoites / Q000254:growth & development / Q000648:ultrastructure; D014774:Virulence
keywords: Amoebic keratitis; cytopathic mechanism; transmission electron microscopy; virulence