''Prototheca wickerhamii'' is a ubiquitous

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

that does not have

chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

. It is widely present in the environment but is a rare cause of opportunistic infection in humans ( protothecosis).

Biology

''P. wickerhamii'' has a round to elliptical cell shape measuring 3–11 μm in diameter. The organism has thick wall (''theca'') with internal septations that form the small wedge-shaped endospores, which are arranged radially and moulded (morula-like form). Reproduction is asexual by release of the spores from the sporangia, which can occur every 5–6 hours in ideal conditions.Lass-Flörl C, Mayr A. Human protothecosis. Clin Microbiol Rev. 2007 Apr;20(2):230-42. Review. PMID 17428884 ''P. wickerhamii'' can be found ubiquitously in the environment as '' Prototheca'' species have been found associated with plants, fresh and sea water as well as the soil. ''P. wickerhamii'' can be cultured on Sabouraud dextrose agar.

Infection

''P. wickerhamii'' can cause opportunistic infections, commonly in individuals with a suppressed immune system due to disease or medication. It is the primary cause of protothecosis in humans. Infection usually results by direct traumatic inoculation and most commonly presents as nodules of the skin. Diagnosis can be made through culture of diseased tissue in Sabouraud dextrose agar or by visualization of sporangia containing sporangiospores on tissue

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

(using

hematoxylin Haematoxylin American and British English spelling differences#ae and oe, or hematoxylin (), also called natural black 1 or Colour Index International, C.I. 75290, is a chemical compound, compound extracted from wood#Heartwood and sapwood, heart ...

/eosin, GMS, or PAS histochemical stains). The organism incites a chronic granulomatous inflammation with infiltrate of histiocytes, lymphocytes, giant cells and occasional eosinophils. Differential diagnosis: Protothecal sporangia may be confused with ''

Coccidioides immitis ''Coccidioides immitis'' is a pathogenic fungus that resides in the soil in certain parts of the southwestern United States, northern Mexico, and a few other areas in the Western Hemisphere. Epidemiology ''C. immitis'', along with its relativ ...

'', which are much larger

Antimicrobial therapy

There is currently no standardized for infection with ''P. wickerhamii''. Positive results of treatment with Voriconazole have been reported as well as with

amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococ ...

. Strains have also showed susceptibility to further azole compounds such as

itraconazole Itraconazole, sometimes abbreviated ITZ, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, blastomycosis, coccidioidomycosis, histoplasmosis, and paracoccidioidomycosis. It may be given ...

and posaconazole.

References

Chlorellaceae Species described in 1959 Chlorophyta species {{green algae-stub