AMOEBA (copy)

Protozoa

unicellular eukaryotic cells

has specialized organelles

Pseudopods

a finger-like specialized organelle that aids in its movement

Amoeba

under class Sarcodina

include free-living organisms

Trophozoite

motile feeding stage

commonly found in watery/liquid stool

Cyst

infective stage

environmentally resistant

most commonly found in formed stool

Sarcodina

Subphylum

Rhizopoda

Superclass

Lobosea

Class

Entamoebidae

Family

Entamoeba

Genus

Entamoeba histolytica

characterized by having a vesicular nucleus, a centrally located small karyosome

lacks organelles

3rd important parasite behind malaria and schistosomiasis

the only pathogenic intestinal amoeba

Entamoeba dispar

Entamoeba moshkovskii

Entamoeba bangladeshi

morphologically similar with Entamoeba histolytica

Encystation

morphologic transformation of trophozoite to cyst

Exystation

morphologic transformation of cyst to trophozoite

Quadrinucleate cyst

is resistant to gastric acidity and desiccation

1. Ingestion of mature cyst

2. Excystation

3. Encystation

4. Cyst passed out in stool; cycle repeats

lifecycle of E. histolytica

Fecal Occult Blood Test (FOBT)

determine if the stool has the presence/absence of blood in it

1. the parasite is a low-virulence strain

2. the inoculation to the host is low

3. the patient’s immune system is intact

3 factors responsible for the asymptomatic state

Amebic colitis

causes flask-shaped amebic ulcers

an intestinal infection caused by the presence of amoeba exhibiting symptoms

Amebic dysentry

a condition characterized by blood and mucus in the stool

Ameboma

clinically presents as mass-lie lesion with abdominal pain and history of dysentery

can be mistaken as carcinoma

Hepatic Amebiasis

Amebic Liver Abscess (ALA)

most common

common in elderly/old patients

formation of abscess in the right lobe of the liver

Right upper quadrant abdominal pain and fever

cardinal manifestation of hepatic amebiasis

Pulmonary amebiasis

second most common

characterized by a liver-colored sputum

Secondary amebic meningoencephalitis

occurs in 1-2%

Venereal amebiasis

men became infected with penile amebiasis after experiencing unprotected sex with a woman who has vaginal amebiasis

trophozoite stage is most commonly observed

transmits sexual

Formalin ether

Ethyl Acetate Concentration test and Merthiolate Iodine Formalin concentration

a more sensitive test than the DFS for the detection of cysts

PCR

Enzyme-linked immunosorbent assay

Isoenzyme analysis

enables differentiation between E. histolytica and E. dispar

Detection of antibodies in stool

a key in the diagnosis of ALA

ultrasound

CT scan

MRI

non-invasive and sensitive methods in early detection of ALA

Metronidazole

drug of choice for the treatment of invasive amebiasis

Diloxanide Furoate

drug of choice for asymptomatic cyst passers

Percutaneous drainage of liver abscess

indicated in patients who don’t respond to Metronidazole and who need prompt symptomatic relief of severe pain

Entamoeba dispar

trophozoite and cyst are morphologically similar to E. histolytica

differs in DNA and ribosomal RNA

isoenzyme pattern is different from that of E. histolytica

Entamoeba moshkovskii

trophozoite and cyst are morphologically similar to E. histolytica

first detected in sewage

shows pathogenicity in experimental trials in animals but non-pathogenic to humans

Entamoeba hartmanii

was at one time designated as a small race to E. histolytica

appearance is similar to E. histolytica but its size is smaller

Entamoeba coli

considerably more common than other human amebae

“DIRTY CYTOPLASM”

Entamoeba polecki

found in the intestines of pigs and monkeys

infects humans rarely

high prevalence in Papua New Guinea

Endolimax nana

known as the smallest amoeba

Iodamoeba butschii

an amoeba that stains well with iodine

Entamoeba chattoni

found in apes and monkey

morphologically identical to E. polecki

detected in 8 human infections

identification is done via isoenzyme analysis

Entamoeba gingivalis

found in the mouth

no cyst stage; trophozoite stage only

moves quickly and has numerous pseudopodia