[Infectiology] Protothecosis

This is a rare infectious disease, caused by Prototheca wickerhamii and Prototheca zopfii.

 

Pathogen profile

• The kingdom Plantae (plants) in the broad sense (plantae sensu lato) includes the group Archaeplastida. Prototheca species are Archaeplastida. All Archaeplastids are autotrophs and all have chloroplasts surrounded by two membranes.
• The subkingdom Viridiplantae (green plants), includes Prototheca and Embryophyta (land plants). The vast majority of terrestrial green plants are embryophytes.
• The phylum Chlorophyta contains many groups of green algae, including the Prototheca species.
• Prototheca are saprotrophic.

 

Classification 

Domain : Eukaryota
Kingdom : Plantae
Subkingdom : Viridiplantae
Infrakingdom : Chlorophyta
Phylum : Chlorophyta
Subphylum : Chlorophytina
Class : Trebouxiophyceae
Order : Chlorellales
Family : Chlorellaceae
Genus : Prototheca
Species :

• P. wickerhamii
• P. zopfii

Symptoms

• Cutaneous lesions
• Olecranon bursitis
• Wound infection
• Disseminated infection 
• Nail infection

 

Complications

• Peritonitis
• Sepsis

 

Risk factors

• Immunodeficiency
• Corticosteroid therapy

 

Epidemiology

There have been at least 160 recorded cases of human protothecosis.

• 13 cases caused disseminated infections.
• 23% of disseminated infections did not occur in immunocompromised patients and did not follow corticosteroid therapy.
• 6 cases caused sepsis.
• 23% of septic cases did not occur in immunocompromised patients and did not follow corticosteroid therapy. 
• 4 cases caused peritonitis
• All 4 cases occured in immunocompromised patients and did not follow corticosteroid therapy.

 

Diagnosis

Protothecosis is almost never suspected clinically.

The definitive diagnosis can be made by morphological identification of the organisms in wet slide preparations of cultures or direct identification in tissue specimens.

Microscopic examination of the organism in culture or in tissue reveals spherical sporangia containing multiple endospores.This gives the organism the appearance of a spoked wheel. Intracellular spores are characteristic for Prototheca species.

 

Management

• Successful treatment with amphotericin B plus tetracycline has been reported in detail in the medical literature.