NEET-PG 2023 - Microbiology PYQs Practice Questions

Q: Claviceps purpurea produces which of the following toxins?

Ergot alkaloids. ***Ergot alkaloids*** - **Claviceps purpurea** is a fungus that infects cereals, particularly rye, and produces a group of toxic compounds known as **ergot alkaloids**. - These alkaloids can cause a condition called **ergotism**, which includes symptoms like hallucinations, gangrene, and severe vasoconstriction. *Aflatoxins* - **Aflatoxins** are produced by species of **Aspergillus fungi**, such as *A. flavus* and *A. parasiticus*, not *Claviceps purpurea*. - They are potent **carcinogens** and are commonly found in contaminated crops like peanuts and maize. *Sanguinarine alkaloid* - **Sanguinarine** is an alkaloid derived from plants like **bloodroot (Sanguinaria canadensis)**, not *Claviceps purpurea*. - It has been linked to **glaucoma** and liver toxicity. *Pyrazolidone drug* - **Pyrazolidone** is a classification of synthetic drugs, often used as **non-steroidal anti-inflammatory drugs (NSAIDs)**, such as phenylbutazone. - This is a pharmaceutical compound and not naturally derived from *Claviceps purpurea* or any fungus. [Practice more Microbiology PYQs on OnCourse]

Q: A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?

Cytomegalovirus (CMV) infection. ***Cytomegalovirus (CMV) infection*** - The presence of cells with an **owl's eye appearance** in urine sediment is a classic histological hallmark of **CMV infection**. - CMV can cause a variety of symptoms in children, including **fever and rash**, making this the most likely diagnosis. *Herpes simplex virus infection* - HSV causes characteristic **vesicular lesions** on mucocutaneous surfaces, often associated with fever. - While HSV can cause systemic illness, it does not typically present with **owl's eye inclusions** in urine cells. *Toxoplasmosis caused by Toxoplasma gondii* - **Toxoplasmosis** can cause fever and rash, especially in congenital infections or immunocompromised individuals. - However, it does not lead to **owl's eye inclusions** in urinary cells, which are pathognomonic for CMV. *Infectious mononucleosis caused by Epstein-Barr virus* - **Infectious mononucleosis** commonly presents with fever, fatigue, and lymphadenopathy, sometimes with a rash. - **Epstein-Barr virus (EBV)** infection does not produce cells with an **owl's eye appearance** in the urine; that is specific to CMV. [Practice more Microbiology PYQs on OnCourse]

Q: A boy presented with a fever and chills. Rapid test was positive for specific antigen HRP-2. Which of the following species of Plasmodium is the most likely causative agent?

Plasmodium falciparum. ***Plasmodium falciparum*** - The **histidine-rich protein 2 (HRP-2)** antigen is specifically produced by **P. falciparum** and is targeted by most rapid diagnostic tests for malaria. - A positive HRP-2 test in a patient with fever and chills indicates a high likelihood of **P. falciparum** infection, which is often the most severe form of malaria. *Plasmodium malariae* - **P. malariae** does not produce **HRP-2 antigen**, therefore, a rapid diagnostic test targeting HRP-2 would be negative for this species. - This species can cause a **quartan fever pattern** (fever every 72 hours) and usually presents with less severe symptoms compared to P. falciparum. *Plasmodium vivax* - **P. vivax** produces **_Plasmodium_ lactate dehydrogenase (pLDH)** and **aldolase antigens**, but not HRP-2. Some rapid tests combine detection of HRP-2 with pLDH to identify both *P. falciparum* and *P. vivax*. - While *P. vivax* causes fever and chills, its presence would not be indicated by a positive HRP-2 specific test alone. *Plasmodium ovale* - **P. ovale** also produces **pLDH and aldolase antigens**, similar to *P. vivax*, and does not produce **HRP-2**. - Infections with *P. ovale* are relatively rare and generally cause milder disease than *P. falciparum*, often with a **tertian fever pattern**. [Practice more Microbiology PYQs on OnCourse]

Q: In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

Detection of microfilariae in the blood smear. ***Detection of microfilariae in the blood smear*** - A positive **filarial antigen test** indicates the presence of adult worms, and the next step is to confirm active infection by identifying **microfilariae**. [1] - **Nocturnal blood samples** are crucial because microfilariae of *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. [1] *Bone marrow biopsy* - This procedure is typically used to diagnose **hematological disorders**, such as leukemia or lymphoma, or investigate causes of unexplained fever, but it is not indicated for filariasis. - While filariasis can rarely lead to **eosinophilia**, a bone marrow biopsy is not a diagnostic tool for filarial infection itself. *DEC provocation test* - The **diethylcarbamazine (DEC) provocation test** is used to bring out microfilariae into the peripheral blood during the daytime for species that exhibit nocturnal periodicity. [1] - However, it carries a risk of severe adverse reactions due to rapid killing of microfilariae, especially in cases of heavy infection, and is generally avoided when antigen tests are positive. [1] *Ultrasound of the scrotum* - Scrotal ultrasound can detect the characteristic "filarial dance sign" (motile adult worms) in the **lymphatic vessels of the scrotum and epididymis**, confirming lymphatic filariasis. [2] - While useful for assessing advanced disease manifestations like **hydrocele**, it does not quantify microfilaremia or replace the need for microscopic confirmation of circulating microfilariae to guide treatment. [Practice more Microbiology PYQs on OnCourse]

Q: A lady from West Rajasthan presented with an ulcer surrounded by erythema on the right leg. Microscopy of the biopsy from the edge of the ulcer showed organisms with dark staining nuclei and kinetoplast. What is the most likely causative agent? (Refer to the provided image)

Leishmania tropica. ***Leishmania tropica*** - The presence of an ulcer with surrounding erythema in **West Rajasthan**, along with microscopy showing organisms with a **nucleus and kinetoplast**, is highly characteristic of **cutaneous leishmaniasis** caused by *Leishmania tropica*. - The organisms seen are **amastigotes** within macrophages in skin lesions, which are identified by their distinct **nucleus and kinetoplast** on microscopy. - West Rajasthan is an **endemic area** for cutaneous leishmaniasis. *Babesia microti* - *Babesia microti* causes **babesiosis**, a tick-borne illness affecting red blood cells, leading to **hemolytic anemia** and malaria-like symptoms. - It does not typically cause **skin ulcers** and its characteristic form in smears is a **ring form or tetrad ("Maltese cross")** within red blood cells, not organisms with kinetoplasts in macrophages. *Trypanosoma brucei* - *Trypanosoma brucei* causes **African trypanosomiasis (sleeping sickness)**, presenting with fever, headaches, joint pain, and neurological symptoms, possibly a **chancre** at the inoculation site. - While it has a **kinetoplast**, it exists as a flagellated **trypomastigote** in the blood and CSF, not as an **amastigote** in macrophages within a skin ulcer. - Additionally, this is **geographically incorrect** for West Rajasthan. *Histoplasma capsulatum* - *Histoplasma capsulatum* is a **fungus** that causes **histoplasmosis**, primarily affecting the respiratory system, especially in immunocompromised individuals. - It does **not possess a kinetoplast** and while it can cause disseminated disease with skin lesions, the microscopic appearance would be **yeast forms** within macrophages, not organisms with kinetoplasts. [Practice more Microbiology PYQs on OnCourse]

Question 1

Claviceps purpurea produces which of the following toxins?

Accepted Answer

Ergot alkaloids

Answer

Aflatoxins

Answer

Sanguinarine alkaloid

Answer

Pyrazolidone drug

Question 2

A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?

Accepted Answer

Cytomegalovirus (CMV) infection

Answer

Herpes simplex virus infection

Answer

Toxoplasmosis caused by Toxoplasma gondii

Answer

Infectious mononucleosis caused by Epstein-Barr virus

Question 3

A boy presented with a fever and chills. Rapid test was positive for specific antigen HRP-2.    Which of the following species of Plasmodium is the most likely causative agent?

Accepted Answer

Plasmodium falciparum

Answer

Plasmodium malariae

Answer

Plasmodium vivax

Answer

Plasmodium ovale

Question 4

In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

Accepted Answer

Detection of microfilariae in the blood smear

Answer

Bone marrow biopsy

Answer

DEC provocation test

Answer

Ultrasound of the scrotum

Question 5

A lady from West Rajasthan presented with an ulcer surrounded by erythema on the right leg. Microscopy of the biopsy from the edge of the ulcer showed organisms with dark staining nuclei and kinetoplast. What is the most likely causative agent? (Refer to the provided image)

Accepted Answer

Leishmania tropica

Answer

Babesia microti

Answer

Trypanosoma brucei

Answer

Histoplasma capsulatum

Question 6

All of the following cause Fournier's gangrene except:

Accepted Answer

Clostridium

Answer

Bacteroides

Answer

Streptococcus

Answer

Staphylococcus

Question 7

In HIV patients, Kaposi's sarcoma is most likely caused by which of the following?

Accepted Answer

Virus

Answer

Bacteria

Answer

Parasite

Answer

Fungus

NEET-PG 2023 — Microbiology