Protozoans Flashcards
What are protozoans?
They are free-living, single celled, eukaryotic cells, with cytoplasm membrane and and cellular organelles (vacoules, endoplasmic reticulum, mitochondria).
Describe how protozoans live and cause harm to humans.
Protozoans have small mouths called cytostome that are capable of ingesting small solid foods like RBCs. They reproduce asexually by replicating their DNA, followed by cell division,or sexually by the fusion of 2 cells, an exchange of DNA, followed by cellular divisions.
They secrete a protective coat (resists the gastric juices) when exposed to chemical agents and changes in temperature. They then shrink into small round armored form called CYST. It is in this form when they cause harm when ingested humans. They get transformed into a motile form called TROPHOZOITE.
What are the 5 intestinal protozoans and the type of diarrhea that they cause?
Entamoeba histolytica causes BLOODY DIARRHEA while and Giardia lamblia and Cyclospora cayetanensis cause NON-BLOODY diarrhea on normal individuals.
Cryptosporidium and Isospora belli cause SEVERE diarrhea on people with defective immune system.
What are the 3 water borne protozoans?
Entamoeba histolytica, Giardia lamblia and Cryptosporidium.
To remember: the Lamb is swimming in water infested by amoeba and cryptonite.
Why is there blood in the stool of E. Histolytica infection?
The trophozoite form invades the intestinal mucosa causing erosions (flask shape ulcers), causing abdominal pain and streaks of mucus and blood in the loose stool. It can become severe with bloody and voluminous diarrhea.
What other severe forms of infections that E. Histolytica can cause?
The trophozoite can enter the portal of blood circulation and form abscesses in the liver, lungs, brain (extra-intestinal amoebiasis). It can lead to death.
How is E. Histolytica diagnosed, treated and prevented?
- A stool exam
A. direct fecal smear) reveals presence of cysts and trophozoites, with or without RBC.
B.Robinson Culture concentration is more sensitive. Can show trophozoites after its division.
C. FECT
D. MIFC (Merthiolate-iodine formality concentration test) - Mucosa scrapes (smear, fixed and stained
- IFAT indirect fluorescent antibody test
- PCR (gold standard) to detect the DNA of E. histolytica
4.Ultrasound and imaging (colonoscopy, sigmoidoscopy) of liver can reveal abscesses. - ELISA for antigens (adherence lectin)
It treated with METRONIDAZOLE (750-800 mg TID 10 days) . (metronidazole also treats Giardia lamblia, Trichomonas vaginalis.
Diloxanide furoate, 500 mg TID for 10 days.
It is prevented by proper disposal of sewage and boiling of water.
How is the shape of E. Histolytica?
The trophozoites has pseudopodia (false feet) that help it move and engulf food
Why is there blood in the stool of those infected with entamoeba histolytica?
How is the shape of Giardia lamblia?
It has 2 forms: CYST and mature trophozoite that is kite-like in shape.
Why is there fat in the stool of those with G. Lamblia?
After ingestion of CYST, it becomes trophozoite in form and adheres to the small intestinal wall. It coats the wall and prevents the absorption of fat. This goes out with the stool and has a horrorific odor. The patient experiences gassy distension and cramps.
To remember: the Lamb is fatty.
How is Giardia lamblia diagnosed, treated and prevented?
- A stool exam
A. direct fecal smear reveals presence of cysts and trophozoites
B.FECT (formalin-ether concentration test)
2. Duodenal entero test to check mucus
3. Duodenal aspirate-biopsy
It treated with METRONIDAZOLE (250 mg TID, 5 days) .
It is prevented by controlling the ingected animals (reservoir) that can contaminate surface water. Sanitation (WASH)
What are the stages in the life of Crytosporidium?
Oocyte (infective) is ingested. Then it exists and releases sporozoites which become enterocytes. These multiples into 8 merozoites by merogony. Merozoites invite other enterocytes or undergo sexual reproduction, producing oocytes which are released into feces.
How does Cryptosporidium infection person?
Through oro-fecal route.
The only test and merozoites interfere with absorption in the small intestines.
For the immunocompromised, there is hypersecretion of fluids and electrolytes (rice water type of stool).
Other organs can be affected leading to acute and gangrene cholecytitis, bronchiolitis and pneumonitis.
How is Cryptosporidium diagnosed, treated and prevented?
Microscopy identifies stained oocytes (using auramine, Kinyoun acid fast and modified Ziehl Neelsen fast stains)
Immunofluorescence also reveals antibodies to oocytes.
It is treated with ORH or IV Fluids and Nitazoxanide.
It is prevented through WASH, boiling of water water avoid swimming in public places.
Which protozoan is sexually transmitted?
Trichomonas vaginalis. Has anterior and posterior flagella and andullating membrane for movement.
Trophozoites are infective causing pruritus, discharge, burning sensation, dysuria, edema- blisters-petechiae in the cervix, vulvo vaginitis.
How is Trichomoniasis diagnosed, treated and prevented?
Dx: Through vaginal swab or urine.
Culture- Feinberg & Whittington medium
PCR
Kato Katz
TX with Metronidazole and Tinidazole.
Prevented: comprehensive vase mgt of STDs
