Blood and Tissue Protozoa Practice Flashcards

A comprehensive set of practice questions covering the properties, life cycles, clinical presentations, and treatments of Toxoplasma gondii and Pneumocystis jiroveci.

What are the two major groups of Blood & Tissue Protozoa mentioned in the lecture?

Sporozoans (Plasmodium, Toxoplasma) and Flagellates (Trypanosoma, Leishmania).

What characteristics define the Apicomplexa (sporozoa) group?

Intracellular protozoans with complex life cycles involving more than one host, gliding motility, and an apical complex for host cell entry.

In the case study of the $54$-year-old HIV patient, what diagnostic finding on a CT scan suggested cerebral toxoplasmosis?

Multiple ring-enhancing lesions in the cerebral cortex.

Which organism is the definitive host for Toxoplasma gondii?

The domestic cat and other felines.

What are the intermediate hosts for Toxoplasma gondii?

Humans and other mammals (humans are considered accidental hosts).

What form of Toxoplasma gondii is responsible for fecal-oral transmission from felines to other animals?

The oocyst, which possesses a thick wall resistant to environmental challenges.

Distinguish between the two types of Toxoplasma trophozoites found in human infections.

Tachyzoites are rapidly growing forms seen in acute infections; bradyzoites are slowly growing forms contained in tissue cysts in muscle, brain, and eye tissue.

How does the sexual reproduction cycle of Toxoplasma gondii occur?

It occurs only in the intestinal tract of felines after the ingestion of tissue cysts; gametes fuse to form oocysts excreted in feces.

What are the primary modes of transmission for Toxoplasma gondii in humans?

Ingestion of raw or undercooked meat (most common), exposure to cat feces, unpasteurized milk, transplacental (vertical), and organ transplantation.

Under what specific condition does congenital infection of the fetus with Toxoplasma occur?

Only when the mother is primarily infected during pregnancy, as only trophozoites pass through the placenta.

What is the clinical significance of Toxoplasma infection in AIDS patients with a CD4 count $< 100\,cells/\mu L$?

They are at high risk for cerebral toxoplasmosis, which presents with fever, headache, seizures, and focal neurological deficits.

What are the classic clinical findings in congenital toxoplasmosis?

Chorioretinitis, diffuse intracranial calcifications, hydrocephalus, and potentially a blueberry muffin rash (petechiae and purpura).

What is the treatment of choice for congenital or disseminated toxoplasmosis?

A combination of sulfadiazine and pyrimethamine.

What is the primary cause of pneumonia in immunocompromised individuals mentioned in the notes?

Pneumocystis jiroveci.

What unique biochemical property distinguishes Pneumocystis jiroveci from most other fungi?

It lacks ergosterol in its membranes and instead contains cholesterol.

How is Pneumocystis jiroveci transmitted?

By inhalation; infection is predominantly localized in the lungs.

What is the characteristic appearance of Pneumocystis pneumonia on a chest X-ray?

Diffuse interstitial pneumonia with bilateral "ground glass" infiltrates extending from the perihilar region.

What is the mortality rate of untreated Pneumocystis pneumonia?

It approaches $100\%$..

Which medication is used for both the treatment and prevention of Pneumocystis jiroveci pneumonia?

Trimethoprim-sulfamethoxazole (TMP-SMX).

What laboratory method is commonly used to diagnose Pneumocystis jiroveci in lung fluids?

Microscopic examination for typical cysts using Giemsa or fluorescent-antibody staining.