Amoebas

• Pseudopods: extension of cytoplasm to function for

locomotion
Two morphologic forms:
• Trophozoites: the form that feeds, multiplies, and
possesses pseudopods; delicate and fragile
• Cyst: nonfeeding stage; has a thick protective cell wall

• Excystation: cyst to trophozoite

• Encystation: trophozoites to cyst

Factors of Encystation - Active vegetative stage, pathogenic stage

• Overabundance or depletion of food supply - Rapid, unidirectional movement

• Marked change in pH - Shape: Irregular

• Increase or decrease oxygen supply - Nucleus: ONE

• Overpopulation - Large nucleus

• Desiccation/ Drying - with relatively small, centrally located karyosome (a small

Factors of Excystation central mass of chromatin)
- Cytoplasmic inclusions: Ingested RBCs
• Osmotic change in medium
- Peripheral chromatin: surrounds the karyosome; fine and
• Enzymatic action of enclosed organism on the inner surface of evenly distributed
the cyst wall - Cytoplasm: finely granular

• Favorable pH of the environment and enzymatic action on the

outer side of the cyst wall CYST
Entamoeba histolytica

Common associated diseases:

• Intestinal amoebiasis
• Amebic colitis
• Amebic dysentery
• Extraintestinal amoebiasis
Entamoeba histolytica

• produces the disease called AMOEBIASIS

• Amoebiasis: means the presence of E. - infective stage

histolytica in an
- Shape: spherical to round
individual WITH or WITHOUT signs and symptoms -
- Nucleus: FOUR
• Worldwide in distribution
- Cytoplasmic inclusions:
• Incidence worldwide: 10%

• More commonly seen in the tropical region - chromatid bar: squared or round-ended; contain RNA
material
- glycogen mass/ vacuoles
TROPHOZOITE
Mode of Transmission
• Fecal-oral route: ingestion of contaminated food or water with
mature cyst SYMPTOMATIC INTESTINAL AMEBIASIS
• Amoebic colitis (Invasive intestinal amebiasis): occurs
• Sexual Contact: anogenital or orogenital tract when the mucosa is invaded
• Amoebic dysentery: a condition characterized by blood
• Vector: flies and cockroache and mucus in the stool; proteolytic enzymes cause
destruction and necrosis of tissue and produces “flask
• Use of human excrement in vegetable garden shape” ulcers on the intestinal mucosa
• Amoebic appendicitis
• Improper/unhygienic food handling • Amoebic granuloma
• Polluted water supply
Amoebic ulcer
LIFE CYCLE

Amoebic colitis

AREAS INVOLVED IN AMOEBIASIS

• Colon; cecum is the most common, followed by
right colon, rectum, sigmoid and appendix
• Hematogenous dissemination may occur, usually to the • Greenish fecal matter, usually its soft to watery.
liver; also, lungs, brain • Also, have greenish with blood streak and mucoid in
• Rectovesical fistula and fistulous involvement of the the stools, this is a usual clinical specimen containing
skin may also occur Entamoeba histolytica

Clinical Symptoms PATHOGENESIS

• Entamoeba histolytica is the only known pathogenic intestinal • Trophozoites lyses the tissue. But before they can lyse the tissue,
amoeba they have to colonize:
• The range of symptoms varies and depends on two major • Factors for Colonization:
factors ➢ Increased in the number of active trophozoites
• the location of the parasite in the host ➢ High pathogenic index of organism
• the extent of tissue invasion
➢ Immunity or nutrition of the host •When they have already
colonized the tissue, they can now lyse the tissue ->>Form
ASYMPTOMATIC AMOEBIASIS
a PRIMARY LESION->> For this lesion, there wouldn’t
• NO signs and symptoms be any signs and symptoms yet
• With presence of organism • They continue to destroy the tissue by lysing it until they reach
• trophozoite is non-invasive the muscularis mucosa.
• “CYST PASSERS” • Muscularis mucosa is somewhat resistant to necrosis. This
• Three factors are responsible for the asymptomatic carrier state necrosis will not extend downward, instead it will extent on the
of a patient infected with E. histolytica: lateral side forming what we call the “FLASK SHAPE” lesion
of Amoebiasis
• the parasite is low-virulence strain
• At the start, they may only have one trophozoite, but this
• the inoculation into the host is low trophozoite multiply by binary fission and they are found in the
• the patient’s immune system is intact periphery
 • As this lesion progresses, this extends to the lateral side → Tissue ➢ Hematogenous Route -> BOTH LUNGS may be
will coalesce → There will be sinus formation affected
• Lesion will continue to progress → Tissue will now peel off ➢ Extension of Amoebic Liver Abscess
forming ulceration ->RIGHT LUNG may be affected
➢ There is destruction of small blood vessel → presence of
blood BRAIN
➢ There is irritation → you may see mucus How can the trophozoite reach the brain?
• Not only small blood vessels are destroyed, but bigger Blood ➢ Hematogenous route
vessels may also be destroyed and trophozoites can now enter the • When it reaches the brain, it will now lyse the tissue
blood vessel →
Patient is still alive SKIN
• This trophozoite will now stimulate the host tissue to react → • Amoebiasis of the skin -> AMOEBIASIS CUTIS • Usually seen
There will be: CELLULAR in the PERIANAL REGION • Amoebiasis occurs in the
PROLIFERATION, INFILTRATION, RECTOSIGMOID
GRANULOMA FORMATION, FIBROSIS region
• There is now a tumor-like lesion called AMOEBIC • Amoebic Liver Abscess can also spread to the side
GRANULOMA or AMOEBOMA → Firm • Also seen in patients with colostomy
in consistency
• Trophozoites can also extend downward and perforate the CLINICAL MANIFESTATION IF INFECTED
intestine Liver o Jaundice - yellow discolorations o
Hepatomegaly o abnormal liver function test (ASt,
EXTRAINTESTINAL AMOEBIASIS ALT,
REMEMBER: bilurubin- increase)
ALMOST ALWAYS, EXTRAINTESTINAL o redness o fever
AMOEBIASIS IS SECONDARY TO Lungs o cough o
INTESTINAL chest pain
o difficulty in breathing o hemoptysis
LIVER (suka dugo) o coughing out of liver
tissue( happens when
How can the trophozoite reach the liver?
there is hepatobronchial fistula)
- Hematogenous route
- Lymphatic route Brain o seizure / convulsion
- Perforation o paralysis o Headache
o vomiting due to severe head ache
- if this occurred in the HEPATIC FLEXURE -> perforation goes
directly to the liver - Trophozoite lyses the tissue forming a single
DIAGNOSIS
abscess -> Amoebic Liver Abscess
History Taking
AMOEBIC LIVER ABSCESS • One important thing that you have to remember when taking
histories of infectious diseases is to know where your
• usually a single lesion
patient came from or the last place your patient visited
• At the right lobe of the liver Physical Exam Laboratory Tests
• seen in males -Fecalysis/ Stool Exam
• described as “ANCHOVY SAUCE-LIKE Amoebic Stools
MATERIAL” ➢ Acidic, few neutrophils, with degenerated RBCs, (+)
➢ Inner portion is liquefied composed of blood, pus, and Charcot Leyden crystals (derived from eosinophils
necrotic liver tissues ➢ If bacillary– alkalinic, many neutrophils (since
➢ Reddish-brown in color bacterial), intact RBCs, (-) Charcot Leyden crsytals
• As the lesion gets bigger, the liver also becomes bigger -Culture Culture the microorganism by Balamuth and Phillip
medium
LUNGS -The simplest thing to do is to do a STOOL EXAM
How will it reach the lungs? ➢ If you get a negative result, repeat the test again
REPEAT AT LEAST 3 TIMES IF THE SAMPLE IS
• Hematogenous route
NEGATIVE
• Extension of Amoebic Liver Abscess- goes into the
subdiaphragmatic area ->into the base of the
➢ You should get the sample from the bloody-mucoid area
of the stool.
RIGHT lung
• If the pathway is through:
TREATMENT •thicker nuclear membrane
• Asymptomatic
• Paromomycin
• Diloxanide furoate (Furamide)
• Metronidazole (Flagyl)
• Symptomatic
• Iodoquinol
• Metronidazole

NON-PATHOGENIC
LIFE CYCLE

Entamoeba coli • Same as Entamoeba histolytica

CYST/MATURE CYST • Entamoeba coli is NON-PATHOGENIC
• Larger with bigger cyst wall •It is a COMMENSAL/LUMEN-DWELLER
• Cytoplasm: Dirty looking •Infective stage: Cyst
• Nucleus: 8 nuclei • Pathogenic Stage: None
➢ with relatively larger karyosome which is eccentrically • Manner of Transmission: Ingestion of viable cyst
located
• Habitat: Large intestine
➢ With coarse, unevenly distributed chromatin granules
underneath the nuclear membrane CLINICAL MANIFESTATIONS
➢ Thicker nuclear membrane
•no signs and symptoms
• If you are going to examine fresh preparation:
➢ You will see presence of multinucleated cyst DIAGNOSIS
➢ You will not see presence of chromatoidal bodies •Stool Examination to demonstrate the
• If chromatoidal bodies are present, they are: Microorganism
➢ Rod-shaped with pointed/jagged/splintered ends
MANAGEMENT
➢ “Whisk-broom” appearance
•Treatment: No specific treatment

Endolimax nana
CYST/MATURE CYST
• Round or ovoidal
• If you are going to examine fresh preparation:
➢ GROUND GLASS APPEARANCE of the
cytoplasm → you don’t see other things
➢ When you add/stain iodine → you will see that the
mature cyst of Endolimax nana has 4 nuclei
• Nucleus: 4 nuclei
TROPHOZOITE ➢ with a large karyosome which may be central or
eccentric in location → it is only the karyosome
• have a larger trophozoite
that you see
• Irregular in shape because of pseudopodia
➢ If karyosome is eccentrically located →
• Characteristic motility: CROSS-EYED APPEARANCE
➢ Sluggish
➢ Non-direction
➢ Non-progressive
• small distinction between the ectoplasm and the
Endoplasm
•Nucleus: 1 nucleus
• Large nucleus
• Large eccentric karyosome
•Coarse, unevenly distributed chromatin granules underneath the
nuclear membrane
TROPHOZOITE
• Also irregular in shape because of the pseudopodia
• Motility: Sluggish
• Narrow rim of ectoplasm
• Nucleus: 1 nucleus
➢ Large karyosome which may be central or eccentric in
location
➢ Cross-eyed appearance of karyosome is not seen

Entamoeba gingivalis
• Habitat in : Buccal cavity
• Seen in the buccal cavity along the tartar of the teeth, tonsil,
and gum
• Common among people with poor oral hygiene
Iodamoeba butschlii • Demonstrated only in the TROPHOZOITE
CYST/MATURE CYST STAGE
• Round/Filiform/ Ovoidal in Shape • Cytoplasm: Granular
•Cytoplasm: Granular • Nucleus: 1 nucleus
•Nucleus: May have 1 to 2 nuclei, but usually has 1 • Karyosome= at the CENTER
➢ With a large karyosome which is centrally or eccentrically • Manner of transmission: Kissing, droplet, sharing of utensils
located •Associated with Trichomonas tenax, which is also found in the
• Diagnostic Feature: PRESENCE OF LARGE buccal cavity
GLYCOGEN VACUOLE •Common also if there is infection in the mouth –
➢ 2/3 of the organism PYURIA ALVEOLARIS
➢ Border: Well-defined; distinct
➢ If you stain the GLYCOGEN VACUOLE:
• Iodine: it will be MAHOGANY BROWN or DARK
BROWN with well-defined border → this is also called
IODINE CYST OF
WENYON
• Iron hematoxylin: COLORLESS (because during fixation
and staining, glycogen is dissolved)

FREE-LIVING AMOEBA
1. Naegleria fowleri
2. Acanthamoeba spp
• Acanthamoeba astrolyxis
• Acanthamoeba castellani
TROPHOZOITE • Acanthamoeba culbertsoni
• also irregular in shape because of pseudopodia • Acanthamoeba polyphaga
• Cytoplasm: Granular
• Nucleus: 1 nucleus Naegleria fowleri
• Produces the disease called PRIMARY
• Diagnostic Feature: PRESENCE OF LARGE
AMOEBIC MENINGOENCEPHALITIS (PAM)
GLYCOGEN VACUOLE → 1/3 of the organism; well defined
border. • Trophozoite
• Amoeboid Form
• Flagellate Form LIFE CYCLE
➢ Aquatic = found in water 1.Cyst form 2.Trophozoites 3.Flagellated form

➢ Highly motile
• Occurs on health individuals
• Infection is ACUTE → like FULMINATING
BACTERIAL MENINGITIS
• The flagellate form will enter nasal mucosa → cross the
cribriform plate → Organism will transform into amoeboid
form → invade the meninges
• If there is inflammation of the meninges
→ MENINGITIS
• Signs and Symptoms of Meningitis:
➢ Severe headache Acanthamoeba
➢ Projectile vomiting • produces the disease called GRANULOMATOUS
AMOEBIC ENCEPHALITIS (GAE)
➢ Nuchal rigidity
• Trophozoite and cyst
• after entering the meninges, it will now enter the brain →
ENCEPHALITIS • Occurs in chronically-ill, debilitated or immunocompromised
patients
• Signs and Symptoms of Encephalitis
• Acquires the organism through the eyes, breaks in the skin,
➢ Headache respiratory tract, and genito-urinary tract
➢ Seizure • Infection is CHRONIC → with GRANULOMA
Flagellate Form FORMATION
Acanthamoeba keratitis
• eyes are involved → “black eye”
• preceded by a trauma
• among those using soft lenses
• also known as “AMOEBIC KERATITIS” DIAGNOSIS
• Tool for Diagnosis: CSF

MANAGEMENT
•Naegleria fowleri: Amphotericin B
Amoeboid Form •Acanthamoeba spp: Sulfadiazine

Trophozoite

Cyst