NEET-PG 2022 - Microbiology PYQs Practice Questions

Q: An HIV patient is admitted with malabsorption, fever, chronic diarrhea, and acid-fast positive organism. What is the likely causative agent?

Isospora. ***Isospora (Cystoisospora belli)*** - **Cystoisospora belli** (formerly *Isospora belli*) is a coccidian parasite common in HIV patients, causing **chronic watery diarrhea**, fever, and malabsorption, especially when the CD4 count is low. - The diagnosis is confirmed by identifying **acid-fast oocysts** in stool samples, which is the key distinguishing feature in this case. - The **acid-fast positive** property makes this the definitive answer among the given options. *Giardia* - **Giardia lamblia** causes malabsorption and chronic diarrhea but is typically characterized by **fatty, foul-smelling stools** and abdominal cramping. - While it can be diagnosed with stool examination, its cysts and trophozoites are **not acid-fast**, which excludes it based on the clinical description. *Microsporidia* - Microsporidia species like **Enterocytozoon bieneusi** can cause chronic diarrhea and malabsorption in HIV patients. - However, they are **intracellular obligate parasites** detected using specialized stains (modified trichrome or calcofluor white) rather than acid-fast staining, making them inconsistent with the **acid-fast positive** finding. *E. histolytica* - **Entamoeba histolytica** causes amebiasis, which can manifest as **amebic dysentery** with bloody stools or chronic non-bloody diarrhea. - Its trophozoites and cysts are **not acid-fast**, and the malabsorption syndrome is less prominent than with Cystoisospora, excluding it from consideration. [Practice more Microbiology PYQs on OnCourse]

Q: Sheathed microfilariae with two nuclei at the tail tip is suggestive of?

Brugia malayi. ***Brugia malayi*** - Microfilariae of *Brugia malayi* are characterized by a **sheathed tail** with **two distinct nuclei** at the very tip of the tail. - This morphological feature, along with the presence of multiple discrete nuclei throughout the body, is key for its identification. *Wuchereria bancrofti* - While *Wuchereria bancrofti* also has a **sheathed tail**, its tail is typically **free of nuclei** or has terminal nuclei that are not distinct or paired. - The nuclei of *W. bancrofti* are more scattered and less clearly defined throughout the body compared to *Brugia*. *Onchocerca volvulus* - *Onchocerca volvulus* microfilariae are **unsheathed** and have a **tapered tail without nuclei**. - They are typically found in the skin, not the blood, and lack the characteristic two nuclei at the tail tip. *Loa loa* - *Loa loa* microfilariae are also **sheathed** but have a **tapered tail with nuclei extending to the tip**, not specifically two distinct nuclei at the tail. - Their nuclei are irregularly arranged within the tail, differentiating them from *Brugia malayi*. [Practice more Microbiology PYQs on OnCourse]

Q: A farmer presents you with a cauliflower-shaped mass on foot, which developed after a minor injury. Microscopy shows copper penny bodies. What is the most likely diagnosis?

Chromoblastomycosis. **Chromoblastomycosis** - The characteristic "cauliflower-shaped" lesion on the foot following a minor injury, especially in a farmer (indicating outdoor exposure), is highly suggestive of chromoblastomycosis. - The presence of **copper penny bodies** (also known as **sclerotic** or **muriform cells**) on microscopy is **pathognomonic** for chromoblastomycosis. *Blastomycosis* - Blastomycosis typically presents with **granulomatous lesions** that can ulcerate but are rarely described as cauliflower-shaped. - Microscopic examination would reveal **broad-based budding yeast cells**, not copper penny bodies. *Sporotrichosis* - Sporotrichosis usually presents as **subcutaneous nodules** that can ulcerate and spread lymphatically, forming a chain of lesions. - Microscopy shows **cigar-shaped budding yeasts** within macrophages or neutrophils, which are distinct from copper penny bodies. *Phaeohyphomycosis* - Phaeohyphomycosis encompasses a broad group of infections by dematiaceous fungi that produce **dark-walled hyphae** or yeast-like cells in tissue. - While it can cause subcutaneous nodules or cysts, the presence of distinct copper penny bodies points away from phaeohyphomycosis as the primary diagnosis. [Practice more Microbiology PYQs on OnCourse]

Q: All of the following statements are true regarding neutrophil extracellular trapping (NET) except for which of the following?

Mitochondrial DNA is seen. ***Mitochondrial DNA is seen*** - NETs (Neutrophil Extracellular Traps) are made primarily of **nuclear chromatin**, not mitochondrial DNA [2]. - The main purpose of NETs is to trap and kill pathogens, focusing on **nuclear genetic material** rather than mitochondrial components. *It is detected in blood during sepsis* - NETs can indeed be found in the **circulation during sepsis**, serving as a defense mechanism against infections. - Their presence in blood indicates an **active immune response**, particularly in severe systemic infections. *It is produced in response to bacterial infection* - NET formation is a known response to **bacterial infections**, as neutrophils deploy them to capture and neutralize pathogens. - This process helps in controlling infections, showcasing the importance of NETs in **innate immunity**. *It is chromatin with antibacterial enzymes* - NETs consist primarily of **decondensed chromatin**, embedded with **antimicrobial proteins** and enzymes to combat pathogens [1][2]. - This characteristic underscores their role in targeting and eliminating invading microorganisms effectively. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 91-92. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 92-93. [Practice more Microbiology PYQs on OnCourse]

Q: A female patient presents with complaints of thick white vaginal secretions. Which of the following can be used to identify the likely species of the causative agent?

CHROMagar. ***CHROMagar*** - **CHROMagar Candida** is a differential and selective medium used for the isolation and presumptive identification of common yeast species, including *Candida albicans*, *Candida tropicalis*, and *Candida glabrata*, based on chromogenic reactions. - Different *Candida* species produce distinct colonies of varying colors on this medium, aiding in their **presumptive identification** directly from patient samples like vaginal secretions. *Birdseed agar* - This medium (also known as Staib's medium or Niger seed agar) is primarily used for the isolation and identification of **Cryptococcus neoformans**, which produces dark brown to black colonies due to its phenoloxidase activity. - While it's a fungal growth medium, it is not optimized for distinguishing common *Candida* species responsible for vaginal candidiasis. *Brain heart infusion agar* - **Brain heart infusion (BHI) agar** is a general-purpose, enriched non-selective medium used for the cultivation of a wide variety of fastidious bacteria, yeasts, and molds. - It does not contain differential components that would allow for the specific identification or differentiation of *Candida* species based on colony color or morphology. *Sabouraud dextrose agar* - **Sabouraud dextrose agar (SDA)** is a selective medium primarily used for the isolation and cultivation of pathogenic and nonpathogenic fungi, including yeasts and molds. - While *Candida* species will grow well on SDA, it does not provide differential characteristics (like distinct colony colors) to allow for the presumptive identification and differentiation of various *Candida* species. [Practice more Microbiology PYQs on OnCourse]

Question 1

An HIV patient is admitted with malabsorption, fever, chronic diarrhea, and acid-fast positive organism. What is the likely causative agent?

Accepted Answer

Isospora

Answer

Giardia

Answer

Microsporidia

Answer

E. histolytica

Question 2

Sheathed microfilariae with two nuclei at the tail tip is suggestive of?

Accepted Answer

Brugia malayi

Answer

Onchocerca volvulus

Answer

Wuchereria bancrofti

Answer

Loa loa

Question 3

A farmer presents you with a cauliflower-shaped mass on foot, which developed after a minor injury. Microscopy shows copper penny bodies. What is the most likely diagnosis?

Accepted Answer

Chromoblastomycosis

Answer

Sporotrichosis

Answer

Blastomycosis

Answer

Phaeohyphomycosis

Question 4

All of the following statements are true regarding neutrophil extracellular trapping (NET) except for which of the following?

Accepted Answer

Mitochondrial DNA is seen

Answer

It is detected in blood during sepsis

Answer

It is chromatin with antibacterial enzymes

Answer

It is produced in response to bacterial infection

Question 5

A female patient presents with complaints of thick white vaginal secretions. Which of the following can be used to identify the likely species of the causative agent?

Accepted Answer

CHROMagar

Answer

Brain heart infusion agar

Answer

Sabouraud dextrose agar

Answer

Birdseed agar

Question 6

A militant presents with rashes all over his body sparing the palms and soles. On examination, he was febrile and lice were noted. Which of the following is responsible for his condition?

Accepted Answer

Rickettsia prowazekii

Answer

Rickettsia typhi

Answer

Rickettsia akari

Answer

Rickettsia conorii

Question 7

A 45-year-old patient with a history of poorly controlled diabetes presents with sinus pain, nasal discharge, and facial swelling. A biopsy reveals broad, nonseptate hyphae branching at wide angles. What is the most likely causative agent?

Accepted Answer

Rhizopus spp.

Answer

Aspergillus fumigatus

Answer

Candida albicans

Answer

Cryptococcus neoformans

Question 8

A patient with HIV presents with extensive anogenital warts. Which HPV types are most commonly associated with malignant transformation in this setting?

Accepted Answer

Types 16 and 18

Answer

Types 42 and 43

Answer

Types 31 and 33

Answer

Types 6 and 11

NEET-PG 2022 — Microbiology