1887

Abstract

Species in the genus are free-living amoebae of the soil and warm fresh water. Although around 30 species have been recognized, is the only one that causes primary amoebic meningoencephalitis (PAM) in humans. PAM is an acute and fast progressing disease affecting the central nervous system. Most of the patients die within 1–2 weeks of exposure to the infectious water source. The fact that causes such fast progressing and highly lethal infections has opened many questions regarding the relevant pathogenicity factors of the amoeba. In order to investigate the pathogenesis of under defined experimental conditions, we developed a novel high- versus low-pathogenicity model for this pathogen. We showed that the composition of the axenic growth media influenced growth behaviour and morphology, as well as cytotoxicity and pathogenicity of Trophozoites maintained in Nelson's medium were highly pathogenic for mice, demonstrated rapid proliferation, characteristic expression of surface membrane vesicles and a small cell diameter, and killed target mouse fibroblasts by both contact-dependent and -independent destruction. In contrast, cultured in PYNFH medium exhibited a low pathogenicity, slower growth, increased cell size and contact-dependent target cell destruction. However, cultivation of the amoeba in PYNFH medium supplemented with liver hydrolysate (LH) resulted in trophozoites that were highly pathogenic in mice, and demonstrated an intermediate proliferation rate , diminished cell diameter and contact-dependent target cell destruction. Thus, in this model, the presence of LH resulted in increased proliferation of trophozoites and enhanced pathogenicity of in mice. However, neither cytotoxicity mechanisms nor the presence of membrane vesicles on the surface correlated with the pathologic potential of the amoeba. This indicated that the pathogenicity of remains a complex interaction between as-yet-unidentified cellular mechanisms.

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2012-10-01
2024-03-28
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