Characterization of a new pathogenic Acanthamoeba Species, A. byersi n. sp., isolated from a human with fatal amoebic encephalitis

J Eukaryot Microbiol. 2013 Nov-Dec;60(6):626-33. doi: 10.1111/jeu.12069. Epub 2013 Jul 24.


Acanthamoeba spp. are free-living amoebae that are ubiquitous in natural environments. They can cause cutaneous, nasopharyngeal, and disseminated infection, leading to granulomatous amebic encephalitis (GAE) in immunocompromised individuals. In addition, they can cause amoebic keratitis in contact lens wearers. Acanthamoeba GAE is almost always fatal because of difficulty and delay in diagnosis and lack of optimal antimicrobial therapy. Here, we report the description of an unusual strain isolated from skin and brain of a GAE patient. The amoebae displayed large trophozoites and star-shaped cysts, characteristics for acanthamoebas belonging to morphology Group 1. However, its unique morphology and growth characteristics differentiated this new strain from other Group 1 species. DNA sequence analysis, secondary structure prediction, and phylogenetic analysis of the 18S rRNA gene confirmed that this new strain belonged to Group 1, but that it was distinct from the other sequence types within that group. Thus, we hereby propose the establishment of a new species, Acanthamoeba byersi n. sp. as well as a new sequence type, T18, for this new strain. To our knowledge, this is the first report of a Group 1 Acanthamoeba that is indisputably pathogenic in humans.

Keywords: 18S rRNA gene; Group 1 Acanthamoeba; human isolate, nuclear small subunit ribosomal RNA gene; ribosomal secondary structure; sequence type T18.

Publication types

  • Case Reports

MeSH terms

  • Acanthamoeba / classification*
  • Acanthamoeba / cytology
  • Acanthamoeba / genetics
  • Acanthamoeba / isolation & purification*
  • Brain / parasitology
  • Central Nervous System Protozoal Infections / parasitology*
  • Cluster Analysis
  • DNA, Protozoan / chemistry
  • DNA, Protozoan / genetics
  • DNA, Ribosomal / chemistry
  • DNA, Ribosomal / genetics
  • Fatal Outcome
  • Genes, rRNA
  • Humans
  • Male
  • Microscopy
  • Middle Aged
  • Models, Molecular
  • Molecular Sequence Data
  • Nucleic Acid Conformation
  • Phylogeny
  • RNA, Protozoan / genetics
  • RNA, Ribosomal, 18S / genetics
  • Sequence Analysis, DNA
  • Skin / parasitology


  • DNA, Protozoan
  • DNA, Ribosomal
  • RNA, Protozoan
  • RNA, Ribosomal, 18S

Associated data

  • GENBANK/AF019064
  • GENBANK/AF019065
  • GENBANK/AF019066
  • GENBANK/DQ185605
  • GENBANK/DQ185607
  • GENBANK/DQ992178
  • GENBANK/GU808277
  • GENBANK/GU808279
  • GENBANK/GU808280
  • GENBANK/GU808282
  • GENBANK/GU808301
  • GENBANK/GU808302
  • GENBANK/KC822461
  • GENBANK/KC822470