Microbiology - chapter 31 - Protozoa

Question 0

What is a cytosome?

Answer 0

The small mouth that protozoa use to ingest solid pieces of food.

Question 1

Describe a protozoa

Answer 1

Free living, single celled, eucaryotic cells. Protozoa have a cytoplasmic membrane and cellular organelles, including 1 or 2 nuclei, mitochondria, food vacuoles and endoplasmic reticulum.

Question 2

What infective form is the protozoa present as when ingested by humans?

Answer 2

A cyst. Then it convert back into the motile form - the trophozoite.

Question 3

Name 5 intestinal protozoa that cause diarrhea.

Answer 3

• Entamoeba Histolytica causes a bloody diarrhea.
• Giardia lamblia & Cyclospora cayetanesis cause a non-bloody diarrhea.
• Cryptosporum & Isospora belli caue severe diarrhea in immuocompromised individuals.

Question 4

The motile feeding form of Entamoeba histolytica is called ………..

Answer 4

The motile feeding form of Entamoeba histolytica is called a trophozoite.

Question 5

Complications oocuring in 10% of individuals infected with Entamoeba histolytica?

Answer 5

The trophozoite invade the intestinal mucosa causing erosions. It may further penetrate the portal circulation, forming abscesses in the liver, followed by spread through the diaphragm into the lung.

Question 6

Giardia lamblia, pathomechanism?

Answer 6

Adheres to the small intestinal wall. The organism coats the small intestinal wall, interfering with intestinal fat absorption. This results in fat-packed feces that smells like, well, shit! Patient presents with abdominal cramps and gassy distension.

Question 7

Trichomonas vaginalis, brief description?

Answer 7

Hangs out in the female vagina and the male urethra. Female patient may present with pruritus, burning on urination, and copious vaginal secretions. Males are usually asymptomatic.

Question 8

Patient presents with a fever, headache, stiff neck, nausea, and vomiting - similar to bacterial meningitis. Low glucose and high protein and neutrophil count in CSF. Patient went swimming a week earlier. Hmmm…?

Answer 8

Naegleria fowleri. 95% of patients die within one week

Question 9

Acanthamoeba and Balamuthia mandrillaris present with clinically similar CNS involvement. What is it?

Answer 9

chronic, granulomatous encephalitis. Typically seen in immunocompromised.

Question 10

The most common CNS infection in AIDS patients?

Answer 10

Toxoplasma encephalitis.

Question 11

Immunocompetent adults who are infected with toxoplasma gondii often develop ………

Answer 11

Immunocompetent adults who are infected with toxoplasma gondii often develop generalized lymphadenopathy.

Question 12

85% of children have had a mild or asymptomatic infection with this organism by the age of four?

Answer 12

Pneumocystis carinii

Question 13

The most common opportunistic infection of AIDS patients?

Answer 13

Pneumocystis carinii pneumonia(PCP)

Question 14

What are the four different protozoa that cause the febrile disease malaria?

Answer 14

1 Plasmodium falciparum
2 Plasmodium vivax
3 Plasmodium ovale
4 PLasmodium malariae

Question 15

The four species of plasmodium that cause malaria lyse RBCs at different time intervals, producing chills, sweats and fevers with different cyclical patterns. Describe these patterns.

Answer 15

Plasmodium falciparum is the most common and deadly plasmodia. It burst red cells more irregularly than the other plasmodia. Every 36-48 hours.

Plasmodium vivax & Plasmodium ovale cause fevers and chills followed by drenching sweats approx every 48 hours - tertian malaria.

Plasmodium malariae lyse RBCs a bit slower, causing fever and chills followed by sweats approx. every 72 hours - quartan malaria.

Question 16

What is the name of the mosquito that carries the plasmodia that cause malaria?

Answer 16

Anopheles mosquito

Question 17

Describe the life cycle of plasmodia.

Answer 17

Sporozoites enter the bloodstream from the anopheles mosquitos sucker marking the pre-erythrocytic cycle. The sporozoites form a ball in the hepatocyte called a trophozoite. The trophozoite undergoes nuclear division, forming thousands of new nuclei - now called a schizont. Then, a cytoplasmic membrane forms around every nucleus, creating thounsands of small bodies called merozoites. The liver cell then bursts open from the overload of merozoites which further enters the bloodstream or infects other hepatocytes. The cells which infects other hepatocytes enters a exo-erythrocytic cycle, whereas the cells that enters RBCs starts the erythrocytic cycle. The merozoites continue to infect RBCs, then grow for 2-3 days followed by another rupture and release into the bloodstream.

Question 18

What group of patients is most severely affected by malaria?

Answer 18

Most deaths occurs in children under 5 years of age, in subsaharan africa. This children often die from cerebral malaria characterized by seizures and impaired conciousness, leading to coma. Even with treatment, 20% of children with cerebral malaria will die.

Question 19

Plasmodia trophozoites effect on erythrocytes?

Answer 19

The trophocytes make RBCs sticky which makes them adhere to each other resulting in plugged arteries. This may cause major complications in the kidneys, lungs(pulmonary edema) and brain.

Question 20

Many African-American and African blacks are resistant to P. falciparum and P. vivax. Why?

Answer 20

The resistance is based on the membrane antigens Duffy a & b that the plasmodium uses for binding.

Question 21

Malaria treatment?

Answer 21

P. malariae, P. vivax and P. ovale are all susceptible to Chloroquine.

P. ovale and P. vivax have exo-erythrocytic life cycles in the liver and will there be protected from Chloroquine. Treatment with Primaquine will kill the liver holdouts.

Artemether will kill Plasmodium falciparum.

Question 22

How are Babesia spread?

Answer 22

By tick bites.

Question 23

Leishmaniasis is transferred to humans by …..

Answer 23

Leishmaniasis is transferred to humans by the sandfly.

Question 24

Three clinical forms of Leishmaniasis?

Answer 24

1 Cutaneous leishmaniasis
2 Mucocutaneous leishmaniasis
3 Visceral leishmaniasis

Question 25

Diffuse Cutaneous Leishmaniasis?

Answer 25

In Venezuela and Ethiopia a chronic form of cutaneous leishmaniasis occurs in immunocompromised patients. The disease is diffuse because of the patientsimmune system do not respond properly to the invasive pathogen.

Question 26

Mucocutaneous leishmaniasis?

Answer 26

Initially a dermal ulcer quite similar to cutaneous leishmaniasis. However, months to years later, mucosal ulcers arise in the mouth and nose.

Question 27

Visceral leishmaniasis?

Answer 27

Caused by Leishmania donovani and Leishmania chagasi. These little basterds invade fixed phagocytic cells(reticuloendothelial system) of the spleen and liver, causing hepatomegaly and massive splenomegaly. Patients also presents with anemia and a possible low white cell count.

Question 28

What two protozoa are responsible for African sleeping sickness?

Answer 28

Tryponosoma brucei rhodesiense & Tryponosoma brucei gambinese

Question 29

How is African sleeping sickness transmitted?

Answer 29

The tsetse fly. Cool name.