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Rhinosporidium seeberi: a human pathogen from a novel group of aquatic protistan parasites

D N Fredricks1, J A Jolley, P W Lepp

  • 1Stanford University, Stanford, California, USA. fredrick@cmgm.stanford.edu

Emerging Infectious Diseases
|May 29, 2000
PubMed

Insights

Rhinosporidium seeberi, previously thought to be a fungus, is actually a novel aquatic parasite. This protist infects humans and animals, belonging to the DRIPs clade of fish and amphibian parasites.

Area of Science:

  • Microbiology
  • Parasitology
  • Mycology

Background:

  • Rhinosporidium seeberi is a microorganism causing infections on mucosal surfaces in humans and animals.
  • Previous classifications based on morphology and histochemistry suggested it was a fungus.

Purpose of the Study:

  • To determine the phylogenetic relationship of Rhinosporidium seeberi.
  • To clarify the taxonomic classification of R. seeberi.

Main Methods:

  • Consensus polymerase chain reaction (PCR) was used to amplify the 18S rRNA gene from infected tissue.
  • Phylogenetic analysis of the amplified gene sequence was performed.
  • Fluorescence in situ hybridization (FISH) and R. seeberi-specific PCR were used to detect the organism in tissues.

Main Results:

  • Phylogenetic analysis revealed R. seeberi is a protist, not a fungus.
  • The organism belongs to a novel clade of aquatic parasites (DRIPs) that infect fish and amphibians.
  • The unique 18S rRNA sequence was confirmed in various infected tissues.

Conclusions:

  • Rhinosporidium seeberi is the first known human pathogen from the DRIPs clade (Ichthyosporea).
  • The study reclassifies R. seeberi as an aquatic protistan parasite, challenging its fungal classification.
  • This finding has implications for understanding parasitic diseases and their evolution.

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