NEET-PG 2020 - Microbiology PYQs Practice Questions

Q: Which interleukin is primarily responsible for inducing IgE production from B cells?

IL-4. ***IL-4*** - **IL-4** is the primary cytokine responsible for promoting B cell differentiation into **plasma cells** that produce **IgE antibodies**. - It plays a crucial role in the development of **allergic reactions** by stimulating IgE class switching. *IL-1* - **IL-1** is a pro-inflammatory cytokine primarily involved in the **innate immune response**, fever, and acute phase reactions. - It does not directly induce IgE production but can modulate immune responses in a broader context. *IL-3* - **IL-3** is a cytokine that primarily supports the growth and differentiation of **hematopoietic stem cells** in the bone marrow. - It is crucial for the development of various blood cell lineages but is not directly involved in IgE class switching. *IL-1 and IL-3* - While both **IL-1** and **IL-3** have important roles in immunity and hematopoiesis, neither directly induces **IgE production** from B cells. - **IL-4** is the specific and most significant interleukin for this function. [Practice more Microbiology PYQs on OnCourse]

Q: The image of an immunoglobulin is shown below. Which type of immunoglobulin is it?

Immunoglobulin A (IgA). ***Immunoglobulin A (IgA)*** - The image depicts two Y-shaped immunoglobulin monomers linked by a central purple component, which represents the **J-chain**, and enveloped by a yellow structure, which represents the **secretory component**. This **dimeric** structure with a secretory component is characteristic of secretory IgA. - **Secretory IgA** is primarily found in mucosal secretions such as saliva, tears, breast milk, and gastrointestinal fluids, where it plays a crucial role in **mucosal immunity** by preventing pathogen adhesion. *Immunoglobulin G (IgG)* - IgG exists as a **monomer** (single Y-shaped unit) in its functional form. - It is the most abundant immunoglobulin in serum and plays a major role in **secondary immune responses** and can cross the placenta. *Immunoglobulin M (IgM)* - In serum, IgM typically exists as a **pentamer**, meaning five Y-shaped units are joined together by a J-chain, forming a star-like structure. - It is the first antibody produced in a **primary immune response** and is effective in complement activation. *Immunoglobulin E (IgE)* - IgE exists as a **monomer** and is primarily associated with **allergic reactions** and defense against parasites. - It binds to receptors on mast cells and basophils, triggering immune responses upon allergen exposure. [Practice more Microbiology PYQs on OnCourse]

Q: Identify the parasite shown in the image.

Trichuris trichiura. ***Trichuris trichiura*** - The image displays characteristic **lemon-shaped** or **barrel-shaped eggs** with distinctive **polar plugs** at each end, which are pathognomonic for *Trichuris trichiura* (whipworm) eggs. - These eggs are thick-shelled and typically measure 50-55 µm by 20-25 µm, containing an undeveloped larva when passed in feces. *Ancylostoma duodenale* - Eggs of *Ancylostoma duodenale* (Old World hookworm) are **oval-shaped** with blunt ends, and a **thin shell**. - They typically contain a **segmented ovum** or an early-stage larva, lacking the polar plugs seen in the image. *Paragonimus westermani* - *Paragonimus westermani* (lung fluke) eggs are generally **oval-shaped** with a **flattened operculum** at one end, which is not visible in the image. - They are larger than *Trichuris* eggs, often measuring around 80-120 µm by 45-70 µm, and are often coughed up in sputum or passed in feces. *Strongyloides stercoralis* - *Strongyloides stercoralis* primarily produces **larvae** (rhabditiform or filariform) in stool samples rather than eggs. - If eggs are seen (rarely, in cases of severe diarrhea), they are small, thin-shelled, and typically contain a developed larva, unlike the eggs shown. [Practice more Microbiology PYQs on OnCourse]

Q: Which of the following cell components produced by Neisseria gonorrhoeae is responsible for attachment to host cells?

Pili (fimbriae). ***Pili (fimbriae)*** - **Pili** are hair-like appendages on the surface of *Neisseria gonorrhoeae* that facilitate initial attachment to **eukaryotic host cells**, particularly epithelial cells in the genitourinary tract. - This attachment is crucial for **colonization** and preventing the bacteria from being washed away by bodily fluids. *Lipooligosaccharide* - **Lipooligosaccharide (LOS)** is a major component of the outer membrane of *Neisseria gonorrhoeae* that contributes to **virulence** through its endotoxin activity, causing inflammation and tissue damage. - While it's important for pathogenicity, its primary role isn't direct attachment but rather the **immune response modulation** and tissue invasion. *IgA1 protease* - **IgA1 protease** is an enzyme produced by *Neisseria gonorrhoeae* that cleaves **IgA1 antibodies**, which are found on mucosal surfaces. - This enzyme helps the bacteria **evade the host immune response** by destroying protective antibodies, not directly mediating cell attachment. *Outer membrane porin protein* - **Outer membrane porin proteins (Porins)** form channels in the outer membrane of *Neisseria gonorrhoeae*, allowing the passage of small molecules. - While important for bacterial metabolism and survival, porins are not the primary structures responsible for **initial host cell attachment**. [Practice more Microbiology PYQs on OnCourse]

Q: Which of the following does not possess superantigen properties?

Vibrio cholerae. ***Vibrio cholerae*** - This bacterium is primarily known for producing **cholera toxin**, which acts on the **adenylate cyclase** pathway to cause severe watery diarrhea. - While it produces powerful toxins, these do not function as **superantigens**, meaning they do not directly bind to MHC class II and T-cell receptors outside the antigen-binding groove. *Streptococcal pyrogenic exotoxins* - These toxins, produced by **Streptococcus pyogenes**, are well-known **superantigens** that cause symptoms such as **scarlet fever** and **streptococcal toxic shock syndrome**. - They bind directly to MHC class II molecules and T-cell receptors, leading to widespread T-cell activation and massive cytokine release. *Staphylococcal enterotoxins* - Produced by **Staphylococcus aureus**, these toxins are a classic example of **superantigens**, causing symptoms such as **food poisoning** and **toxic shock syndrome**. - They bypass conventional antigen presentation, nonspecifically activating a large proportion of T cells and inducing a massive inflammatory response. *None of these* - This option is incorrect because *Vibrio cholerae* stands out as the organism among the choices that does not produce superantigens. - Both streptococcal pyrogenic exotoxins and staphylococcal enterotoxins are well-established superantigens. [Practice more Microbiology PYQs on OnCourse]

Question 1

Which interleukin is primarily responsible for inducing IgE production from B cells?

Accepted Answer

IL-4

Answer

IL-1 and IL-3

Answer

IL-3

Answer

IL-1

Question 2

The image of an immunoglobulin is shown below. Which type of immunoglobulin is it?

Accepted Answer

Immunoglobulin A (IgA)

Answer

Immunoglobulin G (IgG)

Answer

Immunoglobulin M (IgM)

Answer

Immunoglobulin E (IgE)

Question 3

Identify the parasite shown in the image.

Accepted Answer

Trichuris trichiura

Answer

Ancylostoma duodenale

Answer

Strongyloides stercoralis

Answer

Paragonimus westermani

Question 4

Which of the following cell components produced by Neisseria gonorrhoeae is responsible for attachment to host cells?

Accepted Answer

Pili (fimbriae)

Answer

Lipooligosaccharide

Answer

IgA1 protease

Answer

Outer membrane porin protein

Question 5

Which of the following does not possess superantigen properties?

Accepted Answer

Vibrio cholerae

Answer

Staphylococcal enterotoxins

Answer

Streptococcal pyrogenic exotoxins

Answer

None of these

Question 6

Fungal infection which is acquired by traumatic inoculation is?

Accepted Answer

Sporothrix

Answer

Coccidioides

Answer

Paracoccidioides

Answer

Blastomyces

Question 7

A 15-year-old boy presented with fever and chills for 3 days. On examination, he was found to have delayed skin pinch time and dry oral mucosa. Identify the pathogen involved based on the provided peripheral blood smear image.

Accepted Answer

Plasmodium vivax

Answer

Babesia

Answer

Plasmodium falciparum

Answer

Salmonella typhi

Question 8

Superantigen is produced by which of the following?

Accepted Answer

Streptococcus pyogenes

Answer

Clostridium perfringens

Answer

Vibrio cholerae

Answer

Staphylococcus epidermidis

Question 9

A 29 year old male was brought to ED with complaints of nausea, vomiting and abdominal cramps 3-4 hours after eating meat at dinner. What is the likely cause of this condition?

Accepted Answer

Staphylococcus aureus

Answer

Clostridium perfringens

Answer

Clostridium botulinum

Answer

Salmonella Enteritidis

Question 10

A 12 year old boy presents with vomiting within 3 hours of consumption of food at a party. What is the likely causative organism responsible for the symptoms?

Accepted Answer

Staphylococcus aureus

Answer

Clostridium perfringens

Answer

Clostridium botulinum

Answer

Salmonella

NEET-PG 2020 — Microbiology