Week 9 Protozoa Part 1

amebae

single celled and move their own protoplasm using pseudopodia

flagellates

unicellular organisms with flagella for locomotion

spororzoans

apicomplex

microsporidia

ciliates

unicellular covered with cilia that beat to create motion

trophozoite

the motile, feeding stage able to undergo cell division

where are trophozoites often found?

in loose, watery stools

cyst

the dormant, infective stage released to the environment

where are cysts often found?

in formed stools

what are trophozoites and cysts both considered?

diagnostic in fresh or preserved stool specimens

what are the differential characteristics of trophozoites?

number of nuclei present

presence and pattern of peripheral chromatin within the nucleus

appearance of karyosome (irregular aggregation of chromatin in the nucleus)

appearance of cytoplasm

presence of inclusions in cytoplasm (red blood cells, bacteria, yeast)

size of the organism

type of motility exhibited

what are the differential characteristics of cysts?

number of nuclei present

presence and pattern of peripheral chromatin within the nucleus

appearance of karyosome

presence of inclusions in the cytoplasm (chromatoidal bars, glycogen vacuoles)

size of the organism

amebic infections of the eye and CNS

opportunistic free-living amebae capable of causing disease in individuals with compromised immune systems

examples of amebic infections of the eye and CNS

Acanthamoeba spp. (A. lenticulata, A. castellanii, others)

Naegleria spp. (N fowleri only pathogenic species)

what causes amebic conjuctivitis and granulomatous amebic encephalitis (GAE)?

Acanthamoeba spp.

what are signs on the skin of GAE?

granulomatous skin lesons and keratitis and corneal ulcers following corneal trauma or in association with contact lens use

what are meningeal signs of GAE?

headaches, altered mental status, and focal neurologic deficit, which progresses over several weeks to death

what is the infective and diagnostic stage of Acanthamoeba spp.?

trophozoite / cysts and trophozoites in tissue

what are different ways Acanthamoeba spp. (cysts and trophozoites) enter humans?

through the eye, through nasal passages to the lower respiratory tract, through ulcerated or broken skin

what does infection of Acanthamoeba spp. through the eye cause?

results in severe keratitis of the eye

what does infection of Acanthamoeba spp. through the nasal passages to the lower respiratory tract cause?

results in granulomatous amebic encephalitis (GAE) and/or disseminated disease in individuals with compromised immune systemsw

what does infection of Acanthamoeba spp. through ulcerated or broken skin cause?

results granulomatous amebic encephalitis (GAE), disseminated disease, or skin lesions in individuals with compromised immune systems

how are Acanthamoeba infections diagnosed in the laboratory?

microscopic examinations of stained smears (biopsy specimens like brain tissue, skin, cornea OR corneal scrapings which may detect trophozoites and cysts)

immunofluorescence

PCR

Exocyst of Acanthamoeba (10-25 micrometers in diameter)

Wrinkled fibrous outer wall

Endocyst of Acanthamoeba (10-25 micrometers in diameter)

Inner wall (hexagonal)

what causes PAM (primary amebic meningoencephalitis)?

Naegleria fowleri

how is Naegleria fowleri acquired?

by swimming in lakes or ponds

how does Naegleria fowleri enter the body?

through the nose and travel through olfactory nerve to brain

what does Naegleria fowleri cause the human body to experience?

severe headache and other meningeal signs, fever, vomiting, and focal neurologic deficits, and progresses rapidly (<10 days) and frequently to coma and death

what is the infective and diagnostic stage of Naegleria fowleri?

trophozoite / trophozoite in CSF and brain tissue (flagellated forms occassionally in CSF)

how is Naegleria fowleri diagnosed in the laboratory?

microscopic examination of CSF (wet mount may detect motile trophozoites, and a Giemsa-stained smear will show trophozoites with typical morphology

immunofluorescence

PCR

stained with H&E, trophozoite of N. fowleri in CSF (does not form cysts in human tissue)

stained with trichome, trophozoite of N. fowleri in CSF (does not form cysts in human tissue)

immunofluorescence of Acanthamoeba sp

immunofluorescence of Naegleria fowleri