Phylogenetic Analysis of Rhinosporidium seeberi ’s 18S Small-Subunit Ribosomal DNA Groups This Pathogen among Members of the Protoctistan Mesomycetozoa Clade

Abstract

For the past 100 years the phylogenetic affinities ofRhinosporidium seeberi have been controversial. Based on its morphological features, it has been classified as a protozoan or as a member of the kingdom Fungi. We have amplified and sequenced nearly a full-length 18S small-subunit (SSU) ribosomal DNA (rDNA) sequence fromR. seeberi. Using phylogenetic analysis, by parsimony and distance methods, of R. seeberi’s 18S SSU rDNA and that of other eukaryotes, we found that this enigmatic pathogen of humans and animals clusters with a novel group of fish parasites referred to as the DRIP clade (Dermocystidium, rossete agent,Ichthyophonus, and Psorospermium), near the animal-fungal divergence. Our phylogenetic analyses also indicate thatR. seeberi is the sister taxon of the twoDermocystidium species used in this study. This molecular affinity is remarkable since members of the genusDermocystidium form spherical structures in infected hosts, produce endospores, have not been cultured, and possess mitochondria with flat cristae. With the addition of R. seeberi to this clade, the acronym DRIP is no longer appropriate. We propose to name this monophyletic clade Mesomycetozoa to reflect the group’s phylogenetic association within the Eucarya.

A review of the pathology and treatment of canine respiratory infections

“…Nasal disease may rarely be caused by Rhinosporidium seeberi, an aquatic protistan parasite of the Mesomycetozoa family, which some refer to as the DRIP (Dermocystidium, the "rosette agent," Ichthyophonus, Psorospermium) clade. 17,18 Development of mature endospores is stimulated by water exposure, therefore this agent is associated with wet environments. 19 The parasite is endemic in India, Sri Lanka, and Argentina 19 and sporadic cases have been reported in Canada, 20 the United Kingdom, 21 Italy, 22 and the United States.…”

Rhinosporidiosis in the parotid duct: a rare case report

“…Arseculeratne 5 found no evidence of any relationship between M. aeruginosa and R. seeberi. In recent molecular studies, Herr et al 1 suggested that R. seeberi is a protist belonging to a novel group of fish parasites, Mesomycetozoa, which is located phylogenetically between fungal and animal divergence. The protistan nature of this organism was also confirmed by other groups.…”

“…Until recently, Rhinosporidium seeberi (R. seeberi) the causative agent, was categorized as a fungus, but newer findings reveal R. seeberi as a protist belonging to a novel group of fish parasites. 1 Although cases of Rhinosporidiosis have been reported worldwide, it is endemic in South Asia, with the highest incidence in India and Sri Lanka. The four common forms of Rhinosporidiosis are nasal, ocular, cutaneous, and disseminated; however, cases have been reported in the ear, trachea, larynx, brain, urethra, vulva, vagina, and parotid duct.…”

Primary cutaneous rhinosporidiosis diagnosed on FNAC: A case report with review of literature

“…Recent studies suggest that R. seeberi is not a fungus but a protist belonging to a novel group identified as Mesomycetozoa, which is located phylogenetically between the fungal and animal divergence. 3 The mode of transmission of rhinosporidiosis is yet to be demonstrated definitively. The spores probably from animal sources infect humans through air and water.…”