INI-CET 2022 - Microbiology Practice Questions

Q: The viruses of the Filoviridae family like Ebola and Marburg resemble which of the following morphologies?

Filamentous. ***Filamentous*** - Viruses in the **Filoviridae family**, including **Ebola** and **Marburg**, are characterized by their distinct **long, filamentous shape**. - This morphology is a key distinguishing feature visible under electron microscopy, contributing to their namesake ("filo" meaning "thread-like"). *Brick shaped* - **Brick-shaped morphology** is characteristic of **Poxviridae**, such as the **variola virus** (smallpox). - This shape is distinctly different from the thread-like structure of filoviruses. *Bullet shaped* - **Bullet-shaped viruses** are typical of the **Rhabdoviridae family**, which includes the **rabies virus**. - This shape is consistent and easily recognizable for this family, contrasting with the much longer and flexible filaments of filoviruses. *Spherical* - **Spherical morphology** is common among many virus families, including **influenza virus** (Orthomyxoviridae) and **human immunodeficiency virus (HIV)** (Retroviridae). - While many viruses are roughly spherical, filoviruses are specifically known for their elongated, non-spherical appearance.

Q: On Ziehl-Neelsen (ZN) staining oocysts of size 8-10 µm are visible. Identify the organism.

Cyclospora. ***Cyclospora*** - *Cyclospora cayetanensis* oocysts are **spherical** and measure **8-10 µm** in diameter, exactly matching the size described in the question. - They are **partially acid-fast** on ZN staining and may show **internal structures** or appear **wrinkled**, making them visible under microscopic examination. *Microsporidium* - *Microsporidium* are extremely small (**1-4 µm**) **intracellular obligate parasites**, much smaller than the 8-10 µm oocysts described. - They require **special staining methods** and are not typically visible with standard ZN staining due to their minute size. *Cryptosporidium* - *Cryptosporidium parvum* oocysts are **spherical** and measure **4-6 µm** in diameter, which is smaller than the 8-10 µm described. - While they are **acid-fast** on ZN staining, their smaller size distinguishes them from the oocysts in question. *Isospora belli* - *Isospora belli* oocysts are **elongated or oval** and measure **20-30 µm** in length, making them significantly larger than the 8-10 µm oocysts described. - Although they are **acid-fast** and visible on ZN staining, their larger size and oval morphology do not match the question parameters.

Question 1

A forest worker developed skin lesions over the forearm, which initially started as macules but then became nodules. Histology of the nodule shows the following findings. Which of the following is true regarding this condition?

Accepted Answer

It is a dematiaceous fungus

Answer

Angioinvasion is common especially in people with hemolytic anemia

Answer

These bodies are formed by engulfment of the dead fungi by the macrophages

Answer

Infection commonly spreads to involve tendon, muscle and bone

Question 2

The viruses of the Filoviridae family like Ebola and Marburg resemble which of the following morphologies?

Accepted Answer

Filamentous

Answer

Brick shaped

Answer

Bullet shaped

Answer

Spherical

Question 3

On Ziehl-Neelsen (ZN) staining oocysts of size 8-10 µm are visible. Identify the organism.

Accepted Answer

Cyclospora

Answer

Microsporidium

Answer

Cryptosporidium

Answer

Isospora belli

INI-CET 2022 — Microbiology