Subphylum Sarcodina - Entamoeba Histolytica. E. Coli. Balantidium Coli

Question 1

What type are class Sarcodina?

Answer 1

Phylum sarcomastigophora
Intestinal protozoa w/ pseudopodia

ndoplasm, ectoplasm, no organelles

Question 2

What type of protozoa is Balantidium coli

Answer 2

Intestinal ciliates

Question 3

Entamoeba histolytica - Morphology

Answer 3

3 stages - trophozoite, precyst and cyst (15-30um)

Trophozoite -
Shape; not fixed (constantly changing position)
Cytoplasm: cytoplasm is divided into two portion
- clear transparent hyaline ectoplasm
- Granular endoplasm - sometime ingested RBCs, tissue granules and food materials are also found
Nucleus:
- sg sm spherical central
- Central karyosome surrounded by clear halo and anchored to nucleur membrane via linin network (cartwheels appearance)
- N. membrane lined w/ chrmatin distibuted as sm granules
Pseudopodia - aactively motile
- typical crawling/gliding movement
Trophozoites are anaerobic parasite &divide by binary fission, killed by drying, heat + chemical sterilization

Precyst

• Intermediate stage of trophozoite and cyst (smaller)
• round or slightly ovoid with blunt pseudopodium projecting from periphery
• No RBC or food materials in endoplasm.

Cyst - round/oval, slight assym, hyaline body

• young - vacuoles, glyccogen, chromatid bodies (cigar shaped refractile rods), nucleus, karyosome
• immature - simp nucleus
• mature - infective (4 nuclei), glycogen diappear, chromatid bodies may be absent
• cyst wall resistant to digestion by gastric juice in human stomach
• no mitochondria
• survival decrease at v low/high temp

Question 4

E. Histolytica - Lifecycle

Answer 4

Def host - humans (homoxenous)
More common in rural areas w/ lack of sewage

1 - Infect human via ingestion of mature contaminated food/water (fecal contam) or fecal-oral/ oro-genital
2 - mature Cyst is resistant to low pH of stomach, so remain unaffected by the gastric juices.
3 - The cyst wall is then lysed by intestinal trypsin > caecum or lower part of illium > excystation occurs. (neutral or alkaline environment + bile components) > metacyst (quadrinucelated ameba)
4 - metacyst divide > 8 trophozoite > lrg intestine by peristalsis of small intestine
5 - Mature > trophozoites adhere to mucus lining of intestine > secretes proteolytic enzymes > tissue destruction and necrosis.(Parasite, when gain access to blood, migrates > extra-intestinal diseases)
6 - Trop mature > binary fission > precyst secrete cysts wall > uninucleared cyst > mature
7 - cysts released in faeces (immature cysts can mature in ext environment)

Question 5

E. histolytica - Disease

Answer 5

1. Intestinal Amoebiasis
   i. Asymptomatic infection: 90% mild/asymptomatic
   ii. Symptomatic infection
   - Non dysentric amoeboic colitis (mild diarrhea)
   - Acute amoebic dysentery - more common (characterized by abdominal pain, fever and tenderness. Stool contains RBCs, charcot-leyden crystals and trophozoites)
   Complications: toxic megacolon, fulminant amoebic colitis, amoeboma, amoebic peritonitis, perianal ulceration
2. Extra intestinal amoebiasis:
   i. Hepatic infection: non supurative hepatitis, liver abscesses, other complications
   ii. Pulmonary infection: chest pain, dyspnoea, non-productive cough
   iii. Cerebral infection: it is rare and occurs as a complication of liver of pulmonary amoebiasis (brain absecess/tumor)
   iv. Urogen infection: involves kidney and genital organs
   v. Spleenic infection
   vi. Cutaneous amoebiasis - Amoebic pericarditis

Diagnosis
Identify parasite in feces/tissue + serological studies
Acute dysentry - identify trophozoites in liquid stool
Chronic - identify cysts in formed stool

Treatment
Metrondiazole > iodoquinol

Question 6

E. coli - Morphology

Answer 6

Non-pathogenic, frequently commensal in GIT, can be mistaken for E. histolytica

Cyst

• mature have 8 nuclei (precyst have 1)
• oval/irreg

Trophozoites

• distinguish by wide tapered pseudopodia
• coarse granules (histolytica have fine)
• karyosomal chromatin larger
• cytoplasm is coarse often vacuolated (histolytica = finely granular)

Question 7

E. coli - Lifecycle

Answer 7

1 - troph (typically diarrhael) + cyst (typically formed) passed in stool
2 - Ingested as mature cyst in fecally contaminated food, water or formites
3 - Excystion in sm I > trophozoites released > migrate to LI
4 - Binary fission > produce cysts + both stages passed in faeces
(cysts can survive D>W in ext environment due to cell wall, trophozoites rapidly destroyed)

Question 8

Balantidium coli - Morphology

Answer 8

Phylum - ciliaphora

Morphology
Trophozoites - largest intestinal protozoa
- 60um , sac shape
- contracile vacuole, food vacuoles, gullet, mouth
- 2 nuclei : macronucleus(long + kidney-shaped), spherical micronucleus is nestled next to it.
- triangular peristome (opening) ant > cytostome (cell mouth - funnel like)
- lives in lumen, mucosa & submucosa of LI (cecal region & ileum)
Cyst - infective
- smaller (52-55um), round, cyst wall w/ 1/2 layers
- macronucleus only
- cilia and contractile vacuoles are visible in the cyst.

Question 9

B coli - Life cycle & Disease

Answer 9

Life cycle
Host - Humans + pigs
1 - ingestion of infectious cysts,
2 - excystation, and invasion of trophozoites into the mucosal lining of the LI, caecum, and terminal ileum (trophozoite is covered with rows of cilia > aid motility)
N.b similar to histolytica except no multiplication in cyst)

Disease - Balantidiasis
Symtoms
- mucosa/submu invaded & destroyed by multiplying organism
- Acute - 6-15 liquid stool/day (mucus, blood, pus)
- Chronic - diarrhea, constipation, tender colon, anaemia, chachexia
- Many infection asymptomatic
Diagnosis
- Indentify trop in diarrhea stool (less frq cyst in formed stool) - examine several as parasite discharge variablw
- also identify w/ sigmoidoscope
Treatment - Tetracyclines