Biological characterization of a clinical and an environmental isolate of Acanthamoeba polyphaga : analysis of relevant
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ORIGINAL PAPER
Biological characterization of a clinical and an environmental isolate of Acanthamoeba polyphaga: analysis of relevant parameters to decode pathogenicity Bruno da Rocha-Azevedo · Fernando Costa e Silva-Filho
Received: 11 December 2006 / Revised: 22 February 2007 / Accepted: 20 May 2007 / Published online: 14 June 2007 © Springer-Verlag 2007
Abstract Acanthamoeba spp. consists of free-living amoebae, widespread in nature, which occasionally can cause human infections including granulomatous amoebic encephalitis and amoebic keratitis. Acanthamoeba pathogenesis is not entirely known and correlations between pathogenic potential and taxonomy are complex issues. In order to decipher the deWnition of a pathogenic amoeba, the objective of this work was to decipher the deWnition of pathogenic amoeba by characterizing two isolates of Acanthamoeba polyphaga obtained from diVerent origins (a keratitis patient and freshwater), looking for diVerences among them. The clinical isolate grew faster in Peptone-yeast extract-glucose (PYG) medium, transformed more rapidly from a trophozoite to cyst and exhibited increased cytopathic eVect on cultured cells. Morphological diVerences were also noted, since freshwater amoebae presented more acanthopodia than the clinical isolate. Moreover, actin labeling demonstrated that microWlament organization varies between isolates, with the presence of locomotory structures as lobopodia and lamellipodia in the keratitis isolate, which were less adherent on plastic. Zymography demonstrated that the keratitis isolates presented higher proteolytic activity and also were more able to invade collagen matrices. Altogether, we conclude that a group of stable physiological characteristics exist in Acanthamoeba that can be related to pathogenicity.
Communicated by Erko Stackebrandt. B. da Rocha-Azevedo · F. Costa e Silva-Filho (&) Programa de Bioengenharia e Biotecnologia Animal, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ—CCS, bloco G, sala G0-044, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ CEP 21949-900, Brazil e-mail: [email protected]
Keywords Acanthamoeba · Pathogenic protozoa · Free-living amoebae · Isolates characterization · Cytopathic eVect · Proteases · Adhesion · Collagen invasion Abbreviations AE Granulomatous amoebic encephalitis AK Amoebic keratitis PYG Peptone-yeast extract-glucose BSA Bovine serum albumin CPE Cytopathic eVect DTT Dithiothreitol RAPD Random ampliWcation of polymorphic DNA
Introduction Acanthamoeba is a group of free-living amoebae that can be found in diverse natural and artiWcial environments including soil, seawater, freshwater, dust, sediments, vegetation, sewage, air-conditioning units, swimming pools, as well as contact lens cases, among others (Marciano-Cabral and Cabral 2003). These microorganisms are able to survive freely in nature, or endozoically, especially inside mammalian hosts, the reason why Acanthamoeba spp. are called amphizoic amoebae (Schuster and Vivesvara 2004). Under certain
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