INI-CET 2025 - Microbiology PYQs Practice Questions

Q: The Kanagawa phenomenon observed on Wagatsuma agar is characteristic of which of the following organisms?

Vibrio parahaemolyticus. ***Vibrio parahaemolyticus*** - The **Kanagawa phenomenon** describes the ability of certain strains of *Vibrio parahaemolyticus* to produce a **heat-stable direct hemolysin (TDH)**. - This hemolysin causes **beta-hemolysis** (complete clearing) when the organism is grown on a specialized high-salt medium like **Wagatsuma agar**, distinguishing pathogenic strains. *Vibrio cholerae* - This organism causes **cholera** and typically produces yellow colonies on **TCBS agar** (Thiosulfate Citrate Bile Salts Sucrose). - Its primary virulence mechanism is the production of **cholera toxin**, and it does not exhibit the specific Kanagawa phenomenon. *Staphylococcus aureus* - *S. aureus* produces several hemolysins (alpha, beta, delta) but is generally identified using tests like the **coagulase test** and growth on **Mannitol Salt Agar**. - The Kanagawa phenomenon on Wagatsuma agar is a specific test reserved for identifying potentially pathogenic *Vibrio* species. *Burkholderia pseudomallei* - This bacterium causes **melioidosis** and is typically identified by its characteristic **wrinkled colony morphology** on media like Ashdown agar. - It is a Gram-negative bacillus common in Southeast Asia and is not associated with the specific hemolytic action defined by the Kanagawa test. [Practice more Microbiology PYQs on OnCourse]

Q: Which of the following vaccines is contraindicated in a patient of Severe Combined Immunodeficiency (SCID)?

MMR. ***MMR*** - **MMR (Measles, Mumps, Rubella)** is a **live attenuated vaccine**. Live vaccines are absolutely contraindicated in individuals with **Severe Combined Immunodeficiency (SCID)** due to the inability to mount an effective immune response, leading to uncontrolled replication of the vaccinal organism and potentially fatal infection. - SCID causes profound defects in both **T-cell and B-cell immunity**, making the patient susceptible to infections from live vaccines. ***DPT*** - **DPT (Diphtheria, Pertussis, Tetanus)** is an **inactivated (killed) vaccine**; it is safe and typically recommended for SCID patients as it cannot cause the disease. - Only **live vaccines** are contraindicated in SCID, whereas **inactivated or recombinant vaccines** are generally safe. ***Hepatitis B*** - **Hepatitis B vaccine** is a **recombinant vaccine** (inactivated component) and is not contraindicated in patients with SCID. - While the immune response may be suboptimal, the vaccine itself poses no risk of causing the disease. ***IPV*** - **IPV (Inactivated Poliovirus Vaccine)** is a **killed vaccine**. It is safe for SCID patients and must be used instead of the **OPV (Oral Poliovirus Vaccine)**, which is a live vaccine. - Killed vaccines contain non-replicating antigens and thus cannot cause disease, even in highly immunocompromised individuals. [Practice more Microbiology PYQs on OnCourse]

Q: A white patch is observed in the oral cavity of an immunocompromised patient. Which of the following findings is most likely on microscopy?

Pseudo-hyphae. ***Pseudo-hyphae*** - The clinical presentation of a white patch in an immunocompromised patient is highly suggestive of **oral candidiasis** (thrush), typically caused by *Candida albicans*. - In tissue samples (like oral scrapings), *Candida albicans* characteristically appears as **budding yeast** cells along with distinct chains of elongated yeast cells known as **pseudo-hyphae**. ***Branching septate hyphae*** - These structures are characteristic of filamentous fungi, such as **Aspergillus** species or dermatophytes (e.g., *Tinea* infections). - While *Candida* can form true hyphae under certain conditions, **pseudo-hyphae** are the hallmark feature observed in routine smear microscopy for oral candidiasis. ***Budding yeast with capsule*** - This microscopic finding is pathognomonic for **Cryptococcus neoformans**, which causes cryptococcosis. - The capsule is often visualized using special stains like mucicarmine or India ink, and *Cryptococcus* typically causes systemic disease or **meningoencephalitis**, not simple oral thrush. ***Sulfur granules*** - **Sulfur granules** are characteristic aggregates of filamentous bacteria seen in infections caused by **Actinomyces israelii**, leading to **Actinomycosis**. - Actinomycosis usually presents as chronic, indolent abscesses that drain sinus tracts, most commonly in the cervicofacial region. [Practice more Microbiology PYQs on OnCourse]

Q: Acute hemorrhagic conjunctivitis is caused by which of the following combinations?

Coxsackie A and Enterovirus 70. ### **Explanation: Acute Hemorrhagic Conjunctivitis (AHC)** **Acute Hemorrhagic Conjunctivitis (AHC)** is a highly contagious, self-limiting viral infection characterized by rapid onset, lid edema, and pathognomonic **subconjunctival hemorrhages**. #### **1. Why Option A is Correct** The primary etiological agents for AHC are **Enterovirus 70 (EV-70)** and **Coxsackievirus A24 (CA24)** variant. These are small RNA viruses belonging to the *Picornaviridae* family. * **Enterovirus 70** was the first identified cause during the 1969 pandemic. * **Coxsackie A24** is responsible for several subsequent large-scale outbreaks worldwide. #### **2. Why Other Options are Incorrect** * **Options B, C, and D:** These include **Coxsackie B**. While Coxsackievirus B is a common cause of myocarditis, pleurodynia (Bornholm disease), and meningitis, it is **not** a recognized cause of acute hemorrhagic conjunctivitis. The ocular tropism is specific to the **A24 variant** of Coxsackie A. --- ### **High-Yield Clinical Pearls for NEET-PG / INI-CET** * **Incubation Period:** Extremely short, typically **12 to 48 hours**. * **Clinical Hallmark:** Multiple **petechial hemorrhages** on the bulbar conjunctiva that may coalesce to form a large subconjunctival hemorrhage. * **Neurological Association:** A rare but serious complication of **Enterovirus 70** is a **polio-like paralysis** (radiculomyelitis), which can occur several weeks after the conjunctivitis resolves. * **Differential Diagnosis:** * **Epidemic Keratoconjunctivitis (EKC):** Caused by **Adenovirus (Serotypes 8, 19, 37)**. It presents with prominent pseudomembranes and corneal involvement (subepithelial infiltrates) but less frequent hemorrhage compared to AHC. * **Management:** Supportive treatment only (cold compresses, lubricants); antibiotics are used only to prevent secondary bacterial infection. [Practice more Microbiology PYQs on OnCourse]

Question 1

Match the following: 
Vector/agent : 1. Louse - 2. Tick - 3. Mite - 4. Poxvirus
Diseases caused : A. Epidemic typhus - B. Rocky Mounted Spotted Fever (RMSF) - C. Scrub typhus - D. Molluscum contagiosum

Accepted Answer

1-A, 2-B, 3-C, 4-D

Answer

1-B, 2-A, 3-C, 4-D

Answer

1-D, 2-B, 3-C, 4-A

Answer

1-C, 2-B, 3-A, 4-D

Question 2

The Kanagawa phenomenon observed on Wagatsuma agar is characteristic of which of the following organisms?

Accepted Answer

Vibrio parahaemolyticus

Answer

Vibrio cholerae

Answer

Staphylococcus aureus

Answer

Burkholderia pseudomallei

Question 3

Which of the following vaccines is contraindicated in a patient of Severe Combined Immunodeficiency (SCID)?

Accepted Answer

MMR

Answer

IPV

Answer

DPT

Answer

Hepatitis B

Question 4

A white patch is observed in the oral cavity of an immunocompromised patient. Which of the following findings is most likely on microscopy?

Accepted Answer

Pseudo-hyphae

Answer

Branching septate hyphae

Answer

Budding yeast with capsule

Answer

Sulfur granules

Question 5

Acute hemorrhagic conjunctivitis is caused by which of the following combinations?

Accepted Answer

Coxsackie A and Enterovirus 70

Answer

Coxsackie B and Enterovirus 70

Answer

Coxsackie A, Coxsackie B and Enterovirus 70

Answer

Coxsackie A and Coxsackie B

Question 6

Choose the organism identified by the satellite phenomenon shown in the image.

Accepted Answer

Haemophilus influenzae

Answer

Corynebacterium diphtheriae

Answer

Streptococcus pneumoniae

Answer

Klebsiella pneumoniae

Question 7

All of the following are dimorphic fungi except:

Accepted Answer

Cryptococcus

Answer

Coccidioides

Answer

Histoplasma

Answer

Talaromyces

Question 8

Which of the following parasites is capable of causing autoinfection leading to hyperinfection syndrome?

Accepted Answer

Strongyloides stercoralis

Answer

Ascaris lumbricoides

Answer

Ancylostoma duodenale

Answer

Hymenolepis nana

Question 9

A child presents with anal pruritus. Microscopy of the stool sample reveals a plano-convex egg. Identify the pathogen.

Accepted Answer

Enterobius

Answer

Ascaris

Answer

Trichuris

Answer

Ancylostoma

Question 10

Choose the organisms that have two morphological forms: 1. Acanthamoeba 2. Naegleria 3. Giardia 4. Trichomonas

Accepted Answer

1, 3 are correct

Answer

1, 2, 3, 4 are correct

Answer

1, 4 are correct

Answer

1, 2 are correct

INI-CET 2025 — Microbiology