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Investigations of an extraordinary endocytobiont in Acanthamoeba sp.: development and replication

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In this article, the results of investigations concerning a parasitic endocytobiont within the host amoebae (Acanthamoeba sp.) are presented. The endocytobiont was recently isolated from the contact lens and the inflamed eye of a patient with keratitis. Light microscopy and electron microscopy were performed to provide morphological details: Light microscopy revealed the presence of ovoid microorganisms developing and proliferating within the cytoplasm of the amoebic trophozoites. Details of the unusual development of these endocytobionts within the amoebae could be studied and demonstrated by means of electron microscopy. Foldings and morphological reorganization of the microorganisms took place exclusively within the host cytoplasm. The intracellularly aggregating organisms led to the rupture of the Acanthamoeba trophozoites after proliferation. Numerous microorganisms were released, which were infectious and were subsequently ingested by hitherto uninfected acanthamoebic trophozoites. To evaluate the in vitro growth of the isolated endocytobionts (without their hosts), they were transferred to several different culture plates. There was no growth of these unique organisms on five different common cultural plates suitable for the growth of bacteria and fungi.

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  • Barker J, Lambert PA, Brown MRW (1992) Influence of intra-amoebic and other growth conditions on the surface properties of Legionella pneumophila. Infect Immun 61:3503–3510

    Google Scholar 

  • De Jonckheere JF (1977) Use of an axenic medium for differentiation between pathogenic an non-pathogenic Naegleria fowleri isolates. Appl Environ Microbiol 33:751–757

    PubMed  Google Scholar 

  • De Jonckheere JF (1980) Growth characteristics, cytopathic effect in cell culture, and virulence in mice of 36 type strains belonging to 19 different Acanthamoeba spp. Appl Environ Microbiol 39:681–685

    PubMed  Google Scholar 

  • Hoffmann R, Michel R, Müller K-D, Schmid EN (1998) Archaea-like endocytobiotic organisms isolated from Acanthamoeba sp. (Gr II). Endocytobiosis Cell Res 12:185–188

    Google Scholar 

  • Kennedy SM, Devine P et al (1995) Corneal infection associated with Hartmannella vermiformis in contact-lens wearer. Lancet 346:637–638

    Article  CAS  PubMed  Google Scholar 

  • Kirkness CM, Aiken D et al (1993) Vahlkampfiids keratitis simulating Acanthamoeba infection associated with disposable contact lens wear (an overlooked diagnosis). Invest Ophthalmol Vis Sci 334:853

    Google Scholar 

  • Michel R (1997) Freilebende Amöben als Wirte und Vehikel vonMikroorganismen. Mitt Österr Ges Tropenmed Parasitol 19:11–20

    Google Scholar 

  • Michel R (2006) Isolation of free-living amoebae from various sources harbouring pro- and eukaryotic endocytobionts. Endocytobiosis Cell Res 17:127–136

    Google Scholar 

  • Michel R, Schmid EN, Böker T, Hager DG, Müller K-D, Hoffmann R, Seitz HM (2000) Vannella sp. harboring Microsporidia-like organisms isolated from the contact lens and inflamed eye of a female keratitis patient. Parasitol Res 86:514–520

    Article  CAS  PubMed  Google Scholar 

  • Michel R, Muller KD, Schmid EN, Zöller L, Hoffmann R (2003) Endocytobiont KC5/2 induces transformation into sol-like cytoplasm of its host Acanthamoeba sp. as substrate for its own development. Parasitol Res 90:52–56

    CAS  PubMed  Google Scholar 

  • Page FC (1988) A new key to freshwater and soil Gymnamoebae with instructions for culture. Culture collection of algae and protozoa

  • Rowbotham TJ (1980) Preliminary report on the pathogenicity of Legionella pneumophila for freshwater and soil amoebae. J Clin Pathol 33:1179–1183

    Article  CAS  PubMed  Google Scholar 

  • Scheid P (2007) Mechanism of intrusion of a microsporidian-like organism into the nucleus of host amoebae (Vannella sp.) isolated from a keratitis patient. Parasitol Res 101:1097–1102

    Article  CAS  PubMed  Google Scholar 

  • Scheid P (2008) Freilebende Amöben als Krankheitserreger und Vektoren. Wehrmedizinische Monatsschrift 52(Heft 5–6):171–175

    Google Scholar 

  • Scheid P, Pressmar S, Richard G, Zöller R, Michel R (2008) An extraordinary endocytobiont in Acanthamoeba sp. isolated from a patient with keratitis. Parasitol Res 102(5):945–950

    Article  CAS  PubMed  Google Scholar 

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We like to thank Dr. Dave Lam for his support and Elke Schneider for her help and assistance in obtaining these impressive electron micrographs.

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Correspondence to Patrick Scheid.

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Scheid, P., Hauröder, B. & Michel, R. Investigations of an extraordinary endocytobiont in Acanthamoeba sp.: development and replication. Parasitol Res 106, 1371–1377 (2010).

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  • Keratitis
  • Food Vacuole
  • Francisella Tularensis
  • Haemine
  • Intracellular Organism