Infectious disorders
Algal infection - Prototheca

Author: Nat Pernick, M.D. (see Authors page)

Revised: 15 May 2017, last major update July 2011

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Prototheca

Cite this page: Algal infection - Prototheca. website. Accessed June 17th, 2018.
Definition / general
  • Not fungi but similar features
  • First recognized as human pathogen in 1964; two species associated with human disease - P. wickerhamii and P. zopfii
  • Aerobic, achlorophyllous, algae-like, unicellular organisms in water, sewage and soil
  • < 100 cases of human infection reported, usually via trauma or contaminated water, involving face or exposed extremities with erythematous plaques, nodules or superficial ulcers
  • Rarely infects toenails of patients with diabetes (Mycopathologia 2011;172:207)
  • Primary cell or spherule is called the theca; species reproduce by internal septation, forming sporangia which contain up to 20 endospores
  • P. wickerhamii: cells are rounder than the oval/cylindrical shapes of P. zopfii
  • Diagnosis: corn meal agar
Case reports
  • Amphotericin B if disseminated, surgical excision if focal cutaneous or subcutaneous
Clinical images

Images hosted on other servers:

Lesion on foot

Microscopic (histologic) description
  • Necrotizing granulomas of subcutis containing spherical organisms with central basophilia, internal septation and double layer cell walls
  • Also multiple endospores 2 - 4 microns
Microscopic (histologic) images

Images hosted on other servers:

Various images

Internal septation

H&E, GMS and PAS


Positive stains
Additional references