5. Amoeba Flashcards
“false feet”
Pseudopods
Two morphological forms
Trophozoites and cysts
Mode of transmission
Ingestion of infective cyst
the morphologic conversion from the cyst form into the trophozoite form; occurs in the ileocecal area of the intestine
Excystation
conversion of trophozoites to cysts; occurs in the intestine when the environment becomes unacceptable for continued trophozoite multiplication
Encystation
Factors contributing to encystation:
- Ameba overpopulation
- pH change
- Food supply
- Oxygen supply
E. histolytica
Trphozoite:
• MOVEMENT: RAPID, UNIDIRECTIONAL, PROGRESSIVE
• Finger-like hyaline pseudopods
E. histolytica
MATURE CYST –infective ; quadrinucleated ; fine granular cytoplasm
E. histolytica YOUNG
• CHROMATOID BARS –from unorganized chromatin materials; SQUARED AND ROUND-ENDED STRUCTURES THAT CONTAIN RNA
• GLYCOGEN MASS – without defined borders ; stored food ; disappears when the cyst matures
the only known pathogenic intestinal ameba
E. histolytica
(E. histolytica)
ASYMPTOMATIC CARRIER STATE:
• Three factors:
1.LOW-VIRULENCE STRAIN
2. The INOCULATION into the host is LOW
3. The patient’s immune system is INTACT
Symptomatic intestinal Amebiasis
• Amebic dysentery
• Amebic colitis
• FLASK-SHAPED amebic ulcer
• PRIMARY ULCER , PERITONITIS
E. histolytica
SYMPTOMATICEXTRAINTESTINAL AMEBIASIS
• AMEBIC PNEUMONITIS
• VENEREALAMEBIASIS
• PENILE AMEBIASIS /VAGINAL AMEBIASIS
Laboratory diagnosis of e. histolytica
• STOOLEXAM
• SAMPLESFROMSIGMOIDOSCOPYandHEPATICABSCESS
• TYI-S-33
• Antigen test, ELISA, (IHA), (GDP),(IIF)
• Serologic tests- useful in extraintestinal infections.
• Distinguishing invasive and noninvasive strains : isoenzyme electrophoresis and examining the zymodemes
E. histolytica MOT and Vectors
• MOT: Ingestion of infective stage, unprotected sexual contact
• VECTORS: Flies and cockroaches
Once designated as “SMALL RACE”
E. hartmanni
E. hartmanni Trophozoite:
• FINGER SHAPED pseudopods exhibiting NONPROGRESSIVE motility
• Contain ONENUCLEUS
peripheral chromatin PRESENT as evenly distributed granules, “Beaded appearance”
E. hartmanni
E. coli TROPHOZOITES
TROPHOZOITES
• BLUNT PSEUDOPODS which exhibits SLUGGISH, NONPROGRESSIVE MOTILITY • SINGLE NUCLEUS with a LARGE, IRREGULARYSHAPED, ECCENTRIC karyosome which is surrounded by DISTRIBUTED peripheral chromatin UNEVENLY
• KARYOSOME and PERIPHERAL CHROMATIN appear as REFRACTILE STRUCTURES in unstained preparation
E. coli treatment
- Asymptomatic
- Treatment Is Not Indicated
E. coli CYSTS
• THICK WALL surrounds the round to spherical cyst
• Cyst nuclei are readily discernible • One to eight nuclei
• Occasionally, large cyst contain 16 or more nuclei
E. polecki TROPHOZOITES
TROPHOZOITES
* MOTILITY: Sluggish, non-progressive motility in
normal consistency of the stool ; progressive,
unidirectional motility in diarrheal stools
* KARYOSOME: resemble that of E.histolytica
* PERIPHERAL CHROMATIN: resemble that of
E.coli
E. polecki CYSTS
- Spherical to oval in shape
- Contains only ONE NUCLEUS
- Considered primarily a parasite of the pigs and monkeys
- Human infection is relatively rare
- Highest prevalence in Papua, New Guinea
E. polecki
E. polecki TROPHOZOITES
- MOTILITY: sluggish, nonprogressive motility
- BLUNT, HYALINE PSEUDOPODS
- single nucleus
- KARYOSOME: “BLOTLIKE” in appearance
Key feature of e. polecki
ABSENCE OF PERIPHERAL
CHROMATIN
e. polecki cysts
- SPHERICAL,OVOID, or ELLIPSOIDAL
- Most commonly seen mature cyst contains FOUR
nuclie - Large “blot-like” karyosome which is usually
centrally located, absence of peripheral chromatin
I. butschlii trphozoites
- PROGRESSIVE,SLUGGISH motility
- NUCLEUS: large, central karyosome
surrounded by refractive achromatic
granules - PERIPHERAL CHROMATIN:
ABSENT - Coarsely granular and vacuolated cytoplasm may contain bacteria, yeast
cells, and other debris
I. butschlii
- Resembles “basket of flowers” in
shape - SIZE: 8 – 12 um
- Shape may vary (ovoid, ellipsoidal,
triangular) - Contain one nucleus
- Large karyosome is eccentrically
located
I. butschlii lab diagnosis
- Stool Exam
- Iodine Wet Preparations (Cyst)
- Glycogen Mass: takes up the iodine stain ;
remains unstained in trichrome staining - Unstained in Trichome stain: another feature
that aids in identification of I.butschilii
E. gingivalis trphozoites
- Exibits ACTIVE MOTILITY (multiple
pseudopods) - Inclusions: food vacuoles containing
phagocytosed and partially digested
WBCs; epithelial cells; ingested RBCs
causes “Primary Amebic Meningoencephalitis (PAM)”
Naegleria fowleri
THREE KNOWN PATHOLOGIC
FORMS OF N. fowleri:
- Cyst
- Ameboid Trophozoites
- FLAGELLATE Forms
Occurs when the ameboid trophozoites invade the brain,
causing rapid tissue destruction
PRIMARY AMEBIC MENINGOENCEPHALITIS (PAM)
The appearance of resistance or pain during extension of the patient’s knees beyond 135 degrees
Kernig’s sign
N. fowleri treatment
- Prompt and aggressive treatment with AMPHOTERICIN B
- Amphotericin B in combination with RIFAMPIN or
MICONAZOLE - Amphotericin B and Miconazole
- RIFAMPIN – inhibits RNA synthesis
causes “granulomatous amebic encephalitis (gae), acanthamoeba keratitis”
Acanthamoeba spp.
N. fowleri lab diagnosis
- SPECIMEN of CHOICE: CSF
- Brain tissue, corneal scrapings
- Culture on non-nutrient agar with gram-negative bacteria
- Histologic examination
- Calcoflour white
- Technique of choice: Indirect immmunoflourescent antibody
staining
