NEET-PG 2024 - Microbiology PYQs Practice Questions

Q: A frequent traveler presented with 4 days of continuous fever, abdominal pain, and bradycardia. What is the best diagnostic test to confirm the pathogen?

Blood culture. ***Blood culture*** - **Blood culture** is the most sensitive and specific test for confirming **typhoid fever** in the first week of illness. - The presence of **continuous fever** (step-ladder pattern), **abdominal pain**, and **relative bradycardia** in a traveler strongly suggests typhoid fever caused by *Salmonella Typhi*. *Widal test* - The **Widal test** detects antibodies against *Salmonella Typhi* antigens and is often positive later in the disease course. - It has **limited sensitivity and specificity**, especially in endemic areas or with prior vaccination, leading to false positives and negatives. *Urine culture* - **Urine culture** has a low yield for *Salmonella Typhi*, as bacteria are intermittently shed in urine, usually later in the disease. - It's primarily useful for diagnosing **urinary tract infections** or in chronic carriers of typhoid. *Stool culture* - **Stool culture** yield is higher in the later stages of typhoid fever, as *Salmonella Typhi* is shed in feces. - Its sensitivity is lower than blood culture in the early acute phase when bacteremia is most prominent. [Practice more Microbiology PYQs on OnCourse]

Q: An adult patient with a military background is admitted with a rash, fever, altered sensorium, and a deficiency of the membrane attack complex. What is the most likely etiological agent?

Neisseria meningitidis. ***Neisseria meningitidis*** - A deficiency in the **membrane attack complex (MAC)**, particularly **C5-C9 components**, predisposes individuals to recurrent infections with encapsulated bacteria, especially *N. meningitidis*. - *N. meningitidis* is a common cause of **meningitis**, presenting with **fever, altered sensorium**, and often a **petechial rash** due to disseminated intravascular coagulation (DIC), which align with the patient's symptoms. *Klebsiella pneumoniae* - While *K. pneumoniae* can cause severe infections, including pneumonia and meningitis, it is not specifically associated with **MAC deficiency**. - Its infections more commonly manifest as **severe pneumonia** or **urinary tract infections** in immunocompromised patients. *Haemophilus influenzae* - *H. influenzae* can cause meningitis and other invasive infections, especially in children, but it is not typically linked to **MAC deficiency**. - The classic presentation involving **rash** and severe systemic symptoms as described is more characteristic of **meningococcal disease**. *CMV* - **Cytomegalovirus (CMV)** is a herpesvirus that causes a wide range of diseases, particularly in immunocompromised individuals. - However, CMV infections are primarily associated with **cellular immunity defects** rather than a deficiency in the **membrane attack complex** of the complement system. [Practice more Microbiology PYQs on OnCourse]

Q: A patient was admitted with bloody diarrhea after consumption of oysters. The organism exhibits the Kanagawa phenomenon. What is the correct organism?

Vibrio parahaemolyticus. ***Vibrio parahaemolyticus*** - This organism is a common cause of **gastroenteritis** linked to consumption of **raw or undercooked seafood**, especially oysters, and is known for causing **bloody diarrhea**. - The **Kanagawa phenomenon** refers to the production of **thermostable direct hemolysin (TDH)** by *V. parahaemolyticus*, which is a key virulence factor causing hemolysis and is detectable by a specific agar assay. *Staphylococcus aureus* - While *S. aureus* can cause **food poisoning** through its toxins, it typically presents with **nausea, vomiting**, and **abdominal cramps**, not bloody diarrhea. - Food poisoning from *S. aureus* is usually rapid-onset (within hours) and is associated with **improperly handled foods**, particularly those requiring no cooking after preparation (e.g., salads, custards). *Campylobacter jejuni* - This bacterium is a common cause of **bacterial gastroenteritis** and can lead to **bloody diarrhea**, but it's typically acquired from **poultry** or contaminated water, not specifically oysters. - **Guillain-Barré syndrome** is a serious complication that can follow *C. jejuni* infection, which is not characteristic of *Vibrio* infections. *Salmonella typhi* - *Salmonella typhi* causes **typhoid fever**, a systemic illness characterized by **sustained fever, headache, malaise**, and can lead to a "rose spot" rash. - While it can cause gastrointestinal symptoms, **bloody diarrhea is not the predominant symptom**, and raw oyster consumption is not its typical mode of transmission; it's usually spread through contaminated food or water by asymptomatic carriers. [Practice more Microbiology PYQs on OnCourse]

Q: Desert rheumatism is caused by:

Coccidioides immitis. ***Coccidioides immitis*** - This fungus is the causative agent of **coccidioidomycosis**, also known as **Valley fever** or **desert rheumatism**, due to its prevalence in arid regions. - Infection most commonly occurs through inhalation of **arthroconidia** from disturbed soil in endemic areas. *Paracoccidioides brasiliensis* - This fungus causes **paracoccidioidomycosis** (South American blastomycosis), which is endemic to Latin America. - It typically manifests as chronic granulomatous disease affecting the lungs, skin, mucous membranes, lymph nodes, and internal organs. *Candida albicans* - This is a common opportunistic yeast responsible for various infections, from **superficial mucocutaneous candidiasis** (e.g., thrush, vaginal yeast infections) to severe invasive candidemia. - It is not associated with "desert rheumatism." *Cryptococcus neoformans* - This encapsulated yeast is a major cause of **cryptococcosis**, particularly in immunocompromised individuals. - It commonly causes **meningoencephalitis** and pulmonary disease, and is associated with bird droppings, but not "desert rheumatism." [Practice more Microbiology PYQs on OnCourse]

Q: Broad-based budding yeasts are seen in:

Blastomycosis. ***Blastomycosis*** - This fungal infection is classically characterized by **broad-based budding yeasts** seen on microscopic examination. - The yeast cells are typically large and have a characteristic wide connection between the mother and daughter cells during budding. *Histoplasmosis* - Characterized by **small, intracellular yeasts** often seen within macrophages. - These yeasts do **not exhibit broad-based budding**. *Candidiasis* - Primarily presents as **pseudohyphae** (elongated yeast cells resembling hyphae) and budding yeasts (blastoconidia) with **narrow bases**. - **True hyphae** may also be present depending on the species and growth conditions. *Coccidioidomycosis* - In tissue, it is characterized by **spherules** containing **endospores**, not budding yeasts. - The mycelial form is found in culture or environmental samples. [Practice more Microbiology PYQs on OnCourse]

Question 1

A frequent traveler presented with 4 days of continuous fever, abdominal pain, and bradycardia. What is the best diagnostic test to confirm the pathogen?

Accepted Answer

Blood culture

Answer

Widal test

Answer

Urine culture

Answer

Stool culture

Question 2

An adult patient with a military background is admitted with a rash, fever, altered sensorium, and a deficiency of the membrane attack complex. What is the most likely etiological agent?

Accepted Answer

Neisseria meningitidis

Answer

Klebsiella pneumoniae

Answer

Haemophilus influenzae

Answer

CMV

Question 3

A patient was admitted with bloody diarrhea after consumption of oysters. The organism exhibits the Kanagawa phenomenon. What is the correct organism?

Accepted Answer

Vibrio parahaemolyticus

Answer

Staphylococcus aureus

Answer

Campylobacter jejuni

Answer

Salmonella typhi

Question 4

Desert rheumatism is caused by:

Accepted Answer

Coccidioides immitis

Answer

Paracoccidioides brasiliensis

Answer

Candida albicans

Answer

Cryptococcus neoformans

Question 5

Broad-based budding yeasts are seen in:

Accepted Answer

Blastomycosis

Answer

Histoplasmosis

Answer

Candidiasis

Answer

Coccidioidomycosis

Question 6

A female patient presents with dysuria and frequency. A coagulase-negative, novobiocin-resistant Staphylococcus species (>10^4 CFU/mL) was grown in urine culture. What does this indicate?

Accepted Answer

UTI

Answer

Commensal

Answer

Contamination

Answer

Repeat culture needed

Question 7

A patient was diagnosed with Escherichia coli O157:H7 infection. In this designation, what does the "H" stand for?

Accepted Answer

Flagella

Answer

Lipopolysaccharide (LPS)

Answer

Capsule

Answer

Fimbriae

Question 8

A man presents with dysuria and urethral discharge after a history of unprotected sex. The Gram stain of his discharge is shown. What is the best culture medium for isolating the organism responsible?

Accepted Answer

Thayer-Martin agar

Answer

MacConkey agar

Answer

Chocolate agar

Answer

TCBS agar

Question 9

A young boy who used to wash his contact lenses in tap water or with unhygienic lens fluid developed keratitis. Microscopy revealed an organism with spiked or star-shaped structures. Identify the correct organism responsible.

Accepted Answer

Acanthamoeba

Answer

Balantidium

Answer

Pseudomonas

Answer

Staphylococcus aureus

Question 10

A patient in the ICU with a central venous catheter (CVC) develops an infection. Microscopy reveals ovoid budding yeast cells. What is the most likely organism?

Accepted Answer

Candida

Answer

Staphylococcus epidermidis

Answer

Escherichia coli

Answer

Staphylococcus aureus

NEET-PG 2024 — Microbiology