intestinal protozoa quiz - microbio II (cls 54

amoebas, flagellates, cilliates, coccidia, microsporidia galore!

amoeba general characteristics

• Unicellular

• Eukaryotic (more complex than bacteria)

• transmission: ingestion of cysts from food and water contaminated with fecal material

• reproduce by BINARY FISSION (asexual)

  • after replicating its genetic material through mitotic division

  • cell divides into two equal-sized daughter cells

list of amoebas (8)

• Entamoeba histolytica

• Entamoeba dispar

• Entamoeba hartmanni

• Entamoeba coli

• Entamoeba polecki

• Entamoeba nana

• Iodamoeba bütschlii/butschlii/buetschlii

• Blastocystis sp (hominis) (not really an amoeba technically)

amoebic life cycles (general)

1. cysts passed in feces

2. mature cysts ingested (infective & diagnostic stage)

3. in the body:

   • excystation → trophozoite

   • trophozoite multiplicates into another troph and/or cyst

     • cyst undergoes multiple stages before exiting body as a mature cyst

(amoeba) entamoeba histolytica

• one of world's most important parasites due to its worldwide distribution

• only pathogenic intestinal amoeba

• Infants rarely harbor this parasite

• Causes multiple types of infection

  • Gastroenteritis/non-dysenteric amoebiasis

  • Amoebic dysentery

  • Amoebic abscess

  • Amoeboma

    • Sometimes confused with intestinal carcinoma

(entamoeba histolytica) amoeboma

a rare form of invasive amoebiasis

• Associated with abscesses

• Granulomatous mass with a fibrous periphery and inflammatory center

• May cause bowel obstruction and intermittent bleeding

• Easily confused with colon cancer; must be histologically differentiated

(entamoeba histolytica) non-dysenteric infection

• Asymptomatic to mild

• Often a chronic infection

• Symptoms: abdominal pain, nausea, flatulence, irregularity, headaches, fatigue, nervousness

(entamoeba histolytica) amoebic dysentery

• Amoebas eat into intestinal tissues

• Form flask shaped ulcers

• Can perforate the intestine

• Stools consist of blood and mucus--eats RBCs

• "pot bound"

• No fever

(entamoeba histolytica) amoebic abscesses

• Organism carried via portal circulation to liver

• Form sterile abscesses

  • No living orgs inside abscesses

• Amoebas are in the abscess margins

• Lungs are a secondary site

• Patients lack intestinal symptoms

• 10% of untreated cases developed abscesses

(entamoeba histolytica) pathogenicity

• Coinfections by bacteria that cause GI disease may occur

• Pathogenicity related to strain of amoeba

• Possible hyaluronidase production contributes to pathogenicity

• Low protein diets enhance severity

entamoeba histolytica trophozoite

• Thin, delicate chromatin ring

• Central, compact karyosome

• Ingested RBC

  • Not always present

• Size 20 u (usually 15-20; can be 10-60u)

entamoeba histolytica cyst

• Up to 4 nuclei in a cyst—looks the same as the troph nucleus

• Smooth ended chromatid bar

  • Easier seen on trichrome

• 10-15um (can be up to 20u)

entamoeba histolytica life cycle

1. cysts and trophozoites are passed in feces (cysts in formed stool; trophs in diarrhea)

2. excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine

3. trophozoites may remain confined to the intestinal lumen or invade the intestinal mucosa, or blood vessels, reaching extraintestinal sites such as the liver, brain, and lungs

4. trophozoites multiply by binary fission and produce cysts and both stages are passed in the feces

(amoeba) entamoeba dispar

• Morphologically identical to E histolytica

• Does NOT ingest RBCs

• Commensal

• Need serological tests to differentiate

  • Rapid EIA tests for E histolytica

life cycles for Entamoeba coli, E. hartmanni, E. polecki, Endolimax nana, and Iodamoeba buetschlii

all considered nonpathogenic

1. both cysts and trophs of these species are passed in stool and considered diagnostic

   • cysts found in formed stool, whereas trophozoites found in diarrhea

2. excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine

3. trophozoites multiply by binary fission and produce cysts, and both stages are passed in the feces

4. because of the protection conferred by their cell walls, the cysts can survive days to weeks in the external environment and are responsible for transmission

entamoeba harmanni trophozoite

• Looks the same as E histolytica except for size

• 8-10u (5-12u)

• extremely tiny

entamoeba hartmanni cysts

• Same as E histolytica except for size

• 6-8u (5-10u)

entamoeba coli trophozoite

• Sluggish, non-directional motility via pseudopods

• Largest amoeba—up to 50u (20-25u)

• Coarse, irregular (lumpy), chromatin ring

• Eccentric, irregular karyosome

entamoeba coli cyst

• Largest amoeba cyst

  • Up to 35u (15-25u)

  • Easily seen on low power (10x)

• 5 or more nuclei

  • Coarse chromatin ring

  • Eccentric, irregular, karyosome

  • Rare chromatoid bars

    • Splintered ends

(entamoeba coli) chromatoid bar—pic

entamoeba polecki

• Commensal, non-pathogenic

• Usually infects pigs and monkeys

• Often under diagnosed

• Morphology is a mix of E histolytica and E coli

• Difficult to identify unless both cysts and trophs are present on a permanent smear

• Limited to Papua New Guinea, but spreading thru SE Asia

  • Won't be able to visually identify this on tests or in lab

entamoeba polecki trophozoite

• Large nucleus—up to 1/3 of the size of the cyst

• Pleomorphic karyosome (small/large, compact/diffuse, central/eccentric)

• Peripheral chromatin, evenly distributed but can be light or heavy

• Chromatoid bodies highly variable in size and shape

entamoeba polecki cyst

(amoeba) endolimax nana trophozoites & cyst

• Troph has large dense karyosome with thin nuclear membrane—"ball and socket"

  • far right image ; 8-10 um

• Fine granular cytoplasm

• Cyst nuclei looks like potato with eyes

  • 5-10 um (usually 6-8)

• Smallest intestinal amoeba

• "blot karyosome"

(amoeba) iodamoeba bütschlii trophozoite

• Large dense karyosome

• Heavier chromatin (nuclear membrane) than Endolimax nana

• "dirty" cytoplasm

• 12-15u

(amoeba) iodamoeba butschlii cyst

• Single nucleus with large & dense karyosome; 10-12 um

• Crescent halo around karyosome

• Glycogen vacuole ; shimmers at you on wet mount

diagnostic procedures for amoebas

• Visual examination of feces using wet and permanent mounts

  • 6 specimens should be submitted

• Immunological methods for E histolytica

  • Lateral flow EIA--requires non-preserved stool

  • Serum antibody detection: 85% pos in intestinal amoebiasis; 99% pos in extra intestinal cases

• Molecular methods—PCR

(amoeba sort of) blastocystis sp (hominis)

• Ubiquitous, worldwide distribution

• We are still learning about this organism

  • Questionable parasite

  • Has been considered a yeast, flagellate, and an algae

  • Now thought to be most closely related to amoebas

• Seven different subtypes, having different reservoir hosts

• Has pathogenic potential

• Found in up to 25% of healthy people

risk factors for acquiring blastocystis sp

• Immunocompromised health

• Poor hygiene practices

• Be from a developing tropical country

• Travel to a developing tropical country

• Close contact / Exposure to animals

• Consumption of contaminated food & water

(amoeba) blastocystis life cycle

1. Cyst is ingested

2. Excystation in the large intestine

3. Develops into the vacuolar & other forms

4. Encystation during passage thru large intestine

5. Unknown as to cause of transition between forms

(blastocystis) vacoluated / central body form

• Most common form

• Form seen most often in stool specimens

• Enormous variety in size

  • Average 5-40u (but larger ones have been seen)

• Vacuole occupies 90% of the volume

• Nuclei & organelles pushed to periphery

• Vacuole may be ‘empty’ or have fine to flocculent material inside

(blastocystis) granular / amoeboid form

• Granular form

  • Resembles vacuolated form

  • Granules throughout the organism

• Amoeboid form

  • Rarely seen

(blastocytsis) cyst form

• 3-5 um (makes it very hard to find)

• Easily confused with fecal debris

• Environmental form

• Transmissible form

blastocystis disease

• Considered to be an opportunistic pathogen

• Generally self-limiting

• Non-specific symptoms

  • Abdominal pain, bloating, acute or chronic diarrhea, flatulence, nausea, anorexia

• Associated with IBD (Inflammatory Bowel Disease)

diagnosis of blastocystis infections

• Difficult to find and identify in stool samples

• FE concentrate procedure, and permanent stains work well

• Avoid washing sediment in water as this destroys the amoeboid form

  • Not really a problem since they are hard to detect

• No fecal leukocytes present

list of flagellates (6)

• Pathogenic

  • Dientamoeba fragilis

  • Giardia lamblia/intestinalis

  • Trichomonas vaginalis

• Non-pathogenic

  • Trichomonas hominis

  • Trichomonas tenax

  • Chilomastix mesnili

life cycle of flagellates (general)

all flagelletes have the same life cycle; all divide by binary fission

1. cysts & trophs are passed in stool ; trophs do not survive in the environment

2. mature cysts are ingested from contaminated water or hands/fomites

3. cyst develops into troph in small intestine

4. troph divides by binary fission

5. troph releases cyst to repeat cycle

(flagellate) dientamoeba fragilis

• Worldwide distribution

• Occasionally pathogenic

• Morphologically similar to amoebas; no external flagellum

• Symptoms: colicky pains, fatigue, weight loss

• Transmission unknown

• Just discovered a cyst stage

• LIKES TO COINFECT WITH PINWORM!

(flagellate) dientamoeba fragilis life cycle

1. trophozoites are found in the lumen of the large intestine, where they multiply via binary fission, and are shed in the stool

2. whether and in what settings transmission to humans occurs via ingestion of such forms in contrast or in addition to other fecal-oral transmission routes is not yet known

3. transmission via helminth eggs (e.g., via Enterobius vermicularis eggs) has been postulated

dientamoeba fragilis morphological characteristics (troph)

• Size varies: 4-12; 5-15 um

• 20-40% of trophs have one nucleus

• Karyosome often fragmented into 3-5 granules

• No peripheral chromatin around nucleus

• Cytoplasm is ‘dirty’

  • May see vacuoles and granules

• Will not be seen on wet preps or in concentrates

(flagellates) giardia lamblia / intestinalis / duodenalis

• Worldwide distribution; most common parasite in USA

• Pathogenic

• Beavers and other animals are reservoirs

• Seen in campers and those who drink untreated water, kids in daycare, homosexual men

• 12 to 20-day incubation period

• Infects upper small intestine, but does not invade tissues

giardia lamblia / intestinalis / duodenalis life cycle

1. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites)

   • both cysts and trophozoites can be found in the feces (diagnostic stages)

2. In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites)

3. Trophozoites multiply by longitudinal binary fission, remaining free in the lumen of the proximal small bowel or attached to the mucosa by a ventral sucking disk

4. Encystation occurs as the parasites transit toward the colon—cyst is the stage found most commonly in nondiarrheal feces

symptoms of giardia infection

• Acute phase

  • resembles food poisoning, traveler’s diarrhea, viral enteritis, etc

  • Lasts only a few days

  • Flatulence, mushy foul-smelling stools, explosive watery diarrhea, gray green color, greasy looking, nausea, cramps, malaise, abdominal swelling

• Chronic phase – recurrent, brief episodes of loose, foul-smelling, grayish, foamy stools

• Abdominal discomfort & marked distention with belching

(flagellates) giardia trophozoites

• 10-20u

• 2 nuclei

• 2 parabasal bodies

• 1 axostyle

• 8 flagella

• Falling leaf motility

(flagellates) giardia cysts

• Same features as troph, but may have 4 nuclei

• Often stain faintly, can be hard to pick out from background

• Size 11-14u long

diagnostic criteria for giardia

• Demonstrate cysts or trophs in stool samples

  • FE concentrate and Trichrome permanent smear

• Demonstrate trophs in the duodenal contents

  • String test or duodenal biospy

• Irregular shedding pattern

• Collect a minimum of 3 stools on non-consecutive days

• Rapid EIA procedures available

  • Often combined with Cryptosporidium

(flagellates) trichomonas vaginalis

• Urogenital pathogen in men and women

• Only seen in troph stage

• Found in various body sites

  • Urine, vaginal secretions, prostatic secretions

• Transmitted through sexual contact

• Women – itching, burning, dysuria, foamy, yellow-green discharge, foul odor

• Men – usually asymptomatic

  • May see prostatitis, urethritis, epididymitis, urethral stricture

trichomonas vaginalis life cycle

1. Trichomonas vaginalis resides in the female lower genital tract and the male urethra and prostate where it replicates by binary fission

   • does not appear to have a cyst form, and does not survive well in the external environment

2. Trichomonas vaginalis is transmitted among humans, its only known host, primarily by sexual intercourse

(flagellates) other trichomonads

• Trichomonas hominis

  • Non-pathogenic; no cyst

  • Inhabits the colon

  • Difficult to see and recognize in permanent stains

  • Look motile trophs in wet preps

• Trichomonas tenax

  • Non-pathogenic; inhabits the mouth

• Habitat determines species

(flagellates) chilomastix mesnili

• Non-pathogenic

• Lives in cecum & colon

• Trophs have rotating, wobbling motion

chilomastix mesnili life cycle

1. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites)

2. Both cysts and trophozoites can be found in the feces (diagnostic stages)

3. In the large intestine, excystation releases trophozoites

4. Trophs reproduce by binary fission

5. Chilomastix resides in the cecum and/or colon

chilomastic mesnili trophozoites & cysts

• Tear drop shaped troph

  • Eccentric nucleus usually visible

    • Looks like a mouth

  • 10-15u

• Lemon shaped cyst (6-11u)

only known ciliate to infect humans?

balantidium coli

(ciliates) balantidium coli

• Pathogenic

• Largest protozoan parasitizing man

• Lives in Colon & cecum

• Worldwide distribution

  • High endemic areas: Latin America, Philippines, Papua New Guinea, West Iran ; Rare in USA

  • Close association with exposures to live pigs, esp when sanitary conditions are inadequate

    • Poor quality drinking water

• Acquired by ingestion of food or water contaminated by fecal material containing cysts

(ciliates) balantiium coli life cycle

• Human ingests cysts thru contaminated food/water

  • Trophs can’t survive the low pH of stomach

• Excystment followed by maturation

  • Symptoms appear on average 6 days later

• Encystment in the colon and rectum

• Cysts passed in formed feces

risk factors for balantidium coli

• Immunocompromised

• Alcoholism

• Malnourishment

clinical presentations of balantidium coli (4)

• asymptomatic

• chronic

• fulminating balantidiosis

• extraintestinal infection

(balantidium coli) asymptomatic hosts / extraintestinal infection

• Asymptomatic hosts

  • Reservoir of infection

• Extraintestinal Infections

  • Limited mainly to the appendix

(balantidium coli) chronic infection symptoms

• non-bloody diarrhea, cramps, halitosis, nausea, vomiting, tenesmus, abdominal pain

• Symptoms are similar to that of Entamoeba histolytica

(balantidium coli) fulminating balantidiosis

• Mucoid, bloody stools

• Weight loss

• Explosive diarrhea

• Ulceration of the mucosa due to hyaluronidase

• Flask-shaped lesions may form

• Perforation of the colon may occur

balantidium coli trophozoite

• 50-100u

• key features: macronucleus, cytostome, and cilia

• also has a micronucleus; very hard to find

balantidium coli cyst

• 50-70, round with distinct cyst wall

• Macronucleus; no cilia

• Cytotsome—some have this

• usually very circular; almost a perfect circle

list of coccidia (5)

• Cystoisospora (Isospora) belli

• Cryptosporidium parvum

• Cyclospora

• Sarcocystis

• Microsporidia

coccidia (general)

• Obligate tissue parasites

• Inhabit mucosa of small intestine

• Developmental stages resemble malaria

(coccidia) cystoisospora (isospora) belli

• Causes severe intestinal disease

• Infects small intestine

• Diarrhea, nausea, fever, steatorrhea, headache, weight loss

• Big problem in HIV Positive patients

• May produce a toxin

cystoisospora (isospora) belli life cycle

1. At time of excretion, immature oocyst contains one sporoblast

2. after excretion, sporoblast divides in two (oocyst now has two sporoblasts)

   • sporoblasts secrete cyst wall → sporocysts

   • sporocysts divide twice to produce four sporozoites each

3. Infection occurs by ingestion of sporocysts-containing oocysts: the sporocysts excyst in the small intestine and release their sporozoites, which invade the epithelial cells and initiate schizogony

4. Upon rupture of the schizonts, the merozoites are released, invade new epithelial cells, and continue the cycle of asexual multiplication

5. Trophozoites develop into schizonts which contain multiple merozoites

6. After a minimum of one week, the sexual stage begins with the development of male and female gametocytes

7. Fertilization results in the development of oocysts that are excreted in the stool

cystoisospora (isospora) belli oocyst

• Immature stage contains 1 sporoblast

• Mature stage contains 2 sporocysts

• Each contains four sporozoites

• find in wet mount (float above the sediment—focus microscope a little higher up) OR stain w modified acid fast

(coccidia) cryptosporidium parvum

• Infects brush border of columnar epithelial cells of the small intestine

• main reservoir is cattle

• If you have an intact immune system:

  • Profuse, watery diarrhea, mild cramps, nausea, anorexia

  • Lasts 10-15 days, self-cure

• If you have a compromised immune system

  • Same symptoms, but symptoms more severe

  • Becomes a chronic infection, lasting years

  • Develop extraintestinal infections

transmission of cryptosporidium parvum

occurs mainly through ingestion of fecally contaminated water (e.g., drinking or recreational water) or food (e.g., raw milk) or following direct contact with infected animals or people

• oocysts are infectious upon excretion

cryptosporidium parvum life cycle

1. sporulated oocysts, w 4 sporozoites, excreted by host in feces

2. excystation occurs—sporozoites are released and parasitize the epithelial cells of the gastrointestinal tract

3. within the brush border, the parasites undergo asexual multiplication (schizogony/merogony) and then sexual multiplication (gametogony) producing microgamonts (male) and macrogamonts (female)

4. Upon fertilization of the macrogamonts by the microgametes oocysts develop and sporulate in the infected host

   • zygotes give rise to thick- and thin-walled oocysts

   • thick-walled oocysts excreted from the host into the environment ; thin-walled oocysts involved in internal autoinfective cycle and are not recovered from stools

5. oocysts are infectious upon excretion, enabling direct and immediate fecal-oral transmission

(coccidia) cryptosporidium parvum wet mount vs acid fast (pic)

(coccidia testing) direct fluorescent antigen test

used for giardia and cryptosporidium

• Performed on FE concentrate sediment

• Prone to false positives

(coccidia testing) immunocard STAT

used for cryptosporidium an giardia

• Lateral flow EIA test

• Antibodies embedded in membrane

• Performed on unconcentrated preserved feces

(coccidia testing) chromogenic immunoassay

only used for Cryptosporidium

(coccidia) cyclospora

• 8-10 microns

• Emerging pathogen

• Flu-like illness with nausea, vomiting, weight loss, explosive diarrhea

• Lasts 1-3 weeks

• No animal reservoir

• Human feces contaminated food and water

• 2-days to 2-weeks incubation period

(coccidia) cyclospora life cycle

1. oocysts passed in stool sporulate in environment (no fecal oral transmission possible)

2. sporulation occurs after days/weeks at temps between 22°C to 32°C = division of the sporont into two sporocysts, each w 2 elongate sporozoites

3. sporulated oocysts can contaminate fresh produce (basil, cilantro, raspberries) and water which are then ingested

4. oocysts excyst in the gastrointestinal tract, freeing the sporozoites, which invade the epithelial cells of the small intestine

5. inside the cells, they undergo asexual multiplication into type I and type II meronts

   • merozoites from type I meronts likely remain in the asexual cycle

   • merozoites from type II meronts undergo sexual development into macrogametocytes and microgametocytes upon invasion of another host cell

6. fertilization occurs, and the zygote develops to an oocyst which is released from the host cell and shed in the stool

diagnosis of cyclosporiasis

• requires submission of stool specimens for 'Ova and Parasite' testing with additional specific orders for Cyclospora identification

• A single negative stool specimen does not exclude the diagnosis

• 3 specimens are optimal

(coccidia) sarcocystis

• 9-16 microns

• Infects various mammals

• Human: Definitive Host

• Pig: Intermediate Host

• Acquired from improperly cooked or raw beef or pork

(coccidia) sarcocysitis life cycle

1. sporulated oocysts (containing 2 sporocysts) and individual sporocysts can be passed in stool

2. Sporocysts ingested by the intermediate host (cattle/pigs) rupture, releasing sporozoites

3. Sporozoites enter endothelial cells of blood vessels and undergo schizogony → first-gen schizonts

4. Merozoites from first-gen invade capillaries and blood vessels, becoming 2nd-gen schizonts

5. 2nd gen merozoites invade muscle cells and develop into sarcocysts containing bradyzoites = infective stage for the definitive host

6. Humans become infected by eating undercooked meat containing sarcocysts; bradyzoites released from ruptured cysts in small intestine and invade lamina propria of the intestinal epithelium

7. There, they differentiate into macro- and microgametocytes. Fusion of male and female gametes results in the formation of oocysts

8. Oocysts sporulate in the intestinal epithelium and are shed from the host in feces

(coccidia) microsporidia

• 1.5-2 microns

• Obligate intracellular parasite

• Only one species associated with human disease

• Frequently found in HIV Positive patients

• Impossible to find in feces

• Biopsies are best specimen for diagnosis

(coccidia) microsporidia life cycle

1. Infective spore germinates, rapidly everting its polar tubule which contacts the eukaryotic host cell membrane 

2. The spore injects the sporoplasm into the host cell through the polar tubule 

3. sporoplasm enters the proliferative phase marked by extensive multiplication, creating meronts thru binary/ multiple fission

4. meronts undergo sporogony creating sporonts and eventually mature spores when all organelles are polarized

5. when spores increase & completely fill the host cell cytoplasm, the cell membrane is disrupted and spores are released to the surroundings 

6. free mature spores can infect new cells thus continuing the cycle