ENTAMOEBA HISTOLYTICA

 

 

 

Microbiology

Enteric protozoan
Cyst: 5-20 micrometer with one to four nuclei
Trophozoite (ameba): 12-60 micrometer with a single nucleus, a centrally located nucleolus with a uniformly distributed peripheral chromatin
Many strains, differentiated by isoenzyme analysis

Epidemiology

10% of the world is infected 
50,000-100,000 E. histolytica-associated deaths per year (third leading parasitic cause of death in the world)
Endemic in Mexico, India, West and South Africa and portions of Central and South America
Vast majority (90%) of patients remain asymptomatic
High risk factors for invasive diseases in North America: 
recent immigration, institutionalization and homosexuality
Transmission by fecal-oral route

Clinical syndromes

Intestinal:
Asymptomatic colonization
Acute amebic colitis
Fulminant colitis
Ameboma
Extraintestinal
Hepatic abscess
Pleuropulmonary
Peritonea
Pericardial
brain abscesses

Diagnosis

Serology (generally positive after 7 days)
Cyst and parasite in stool (rapid examination after special coloration: modify Kinouyn: as trophozoites die rapidly)

Comments on treatment

Surgical drainage if abscess
Asymptomatic cyst passer:
recommended: Paromomycin or Iodoquinol
alternative: diloxanide furoate
Diarrhea
recommended: Metronidazole and (Paromomycin or Iodoquinol)
alternative: (tinidazol or ornidazole) and (Paromomycin or Iodoquinol)
Extraintestinal infection: 
Metronidazole and Iodoquinol