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Acanthamoeba castellanii is a model for eukaryote-prokaryote interaction and a human pathogen

Abstract number: 1733_39

Abd H., Saeed A., Advinsson B., Sandström G.

Objectives:A. castellanii is a free-living amoeba inhabiting aquatic environments and isolated from different environments. The aim is to study its features, its interaction with pathogenic bacteria and its detection from samples.

Methods: Cultivation, viable count, PCR and microscopy.

Results:A. castellanii grew tenfold and survived for more than 30 days showing a long survival time compared to survival of macrophages. We found that trophozoites as well as cysts emitted autofluorescence helping in the diagnosis of Acanthamoeba and its viability. It is well known that trophozoites feed on different cells by phagocytosis. We observed that A. castellanii could also take up trophozoite or cyst from its cell cultures.

The importance of Acanthamoeba species is their ability to be predators or hosts to different bacteria. Our studies showed that the facultative intracellular bacterium Francisella tularensis multiplied inside vacuoles of A. castellanii while the extracellular bacterium Pseudomonas aeruginosa killed this amoeba by type III secretion system effector's proteins. Surprisingly, Vibrio cholerae that is considered as an extracellular bacterium multiplied in the cytoplasm of A. castellanii and behaved same behaviour of the facultative intracellular bacteria Shigella sonnei and S. dysenteriae.

Several Acanthamoeba species are human pathogens. The trophozoites enter human body through respiratory tract, injured skin, invade the central nervous system to cause granulomatous amoebic encephalitis and colonise the cornea causing amoebic keratitis. As evidence to the increasing importance of Acanthamoeba infections, we diagnosed the first Nordic case of fatal meningoencephalitis and two cases of amoebic keratitis caused by A. castellanii.

Conclusions: Characteristics of A. castellanii such as long life because of encystation as well as excystation, phagocytosis, autofluorescence, resistance to many antibiotics, predator, host and victim to different bacteria, make it an ideal unicellular organism to study the interaction between eukaryotes and prokaryotes and to be used as a powerful tool for the culture of some intracellular bacteria in addition to its increased role as human pathogen.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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