NEET-PG 2024 Practice Questions

Q: A patient presents with painful vesicles as shown in the image. What is the diagnosis?

Herpes. ***Herpes*** - The image shows a cluster of **small, painful vesicles on an erythematous base**, which is highly characteristic of a herpes simplex virus (HSV) infection. - These lesions typically evolve into ulcers, crust over, and heal, and are often recurrent. *Chancroid* - Chancroid presents as **painful, soft chancres** (ulcers) with irregular, undermined borders and a gray or yellow base, often accompanied by **buboes** (enlarged, tender lymph nodes). - It does not typically manifest as clusters of small vesicles. *Syphilis* - Primary syphilis presents as a **painless chancre**—a single, firm, ulcerated lesion with a clean base and raised borders. - Secondary syphilis can cause a variety of skin manifestations, but not painful vesicles. *Candidiasis* - Cutaneous candidiasis usually appears as a **red, moist rash with satellite lesions** (smaller papules or pustules spreading from the main rash), often in skin folds. - While it can be inflammatory and itchy, it does not typically form discreet painful vesicles as seen in the image.

Q: A 40-year-old farmer presents with fever, calf tenderness, conjunctival suffusion, retro-orbital pain, and hypokalemia. What is the diagnosis?

Leptospira. ***Leptospira*** - The combination of **fever**, **calf tenderness**, **conjunctival suffusion** (red eyes without purulent discharge), **retro-orbital pain**, and **hypokalemia** is highly suggestive of **leptospirosis**. - A farmer's occupation increases the risk of exposure to contaminated water or soil, which is a common transmission route for Leptospira. - **Calf tenderness** and **conjunctival suffusion** are particularly characteristic features. *Malaria* - Characterized by **cyclic fevers**, **chills**, and **sweats**, often with **splenomegaly** and **anemia**. - **Calf tenderness**, **conjunctival suffusion**, and **retro-orbital pain** are not typical primary symptoms of malaria. *Dengue* - Often presents with **high fever**, **severe headache** (especially retro-orbital), **muscle and joint pain** ("breakbone fever"), and **rash**. - **Conjunctival suffusion** and significant **calf tenderness** are not classic features, and hypokalemia is less common than with leptospirosis. *Influenza* - Acute respiratory illness with **fever**, **cough**, **sore throat**, **muscle aches**, and **fatigue**. - While muscle aches can occur, **calf tenderness**, **conjunctival suffusion**, and **hypokalemia** are not characteristic of influenza. *Typhoid fever* - Presents with **sustained fever**, **relative bradycardia**, **rose spots**, and **hepatosplenomegaly**. - **Conjunctival suffusion**, **calf tenderness**, and **retro-orbital pain** are not typical features of typhoid fever.

Q: A patient living with HIV presents with foulsmelling stools. Microscopic examination of the stool reveals no cysts or ova, but a 200-micrometer larva is observed. What is the most likely pathogen?

Strongyloides stercoralis. ***Strongyloides stercoralis*** - The presence of **larvae** in the stool [2], particularly **rhabditiform larvae**, is characteristic of *Strongyloides stercoralis* infection, as this parasite has an **autoinfective cycle** involving larval stages in the human host [2]. - In HIV-positive patients, *Strongyloides* can cause **hyperinfection syndrome**, leading to severe gastrointestinal symptoms like foul-smelling stools, and increased larval shedding [2]. *Ascaris lumbricoides* - *Ascaris lumbricoides* is a large intestinal nematode, but it typically presents with **ova** (eggs) in the stool, not larvae, as the eggs hatch in the small intestine. - While it can cause gastrointestinal symptoms, the hallmark microscopic finding in stool samples is the presence of **mammillated or decorticated eggs**. *Ancylostoma duodenale* - *Ancylostoma duodenale* (hookworm) infections are identified by the presence of **eggs** in the stool [1], which are typically oval with a thin shell and contain a developing larva. - Hookworm larvae usually develop in **soil** and infect humans through skin penetration, rather than being commonly found in stool samples from intestinal infection [1]. *Schistosoma mansoni* - *Schistosoma mansoni* is a **blood fluke** that causes intestinal schistosomiasis, characterized by the presence of **spined eggs** in the stool. - The parasite's life cycle involves **freshwater snails** as intermediate hosts, and a **larval stage (cercariae)** that penetrates human skin, but larvae are not typically found in human stool.

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.

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.

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."

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.

Q: 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?

UTI. ***UTI*** - The isolation of a **coagulase-negative, novobiocin-resistant Staphylococcus** in a patient with UTI symptoms suggests **_Staphylococcus saprophyticus_**, a common cause of UTIs in young women. - A bacterial count of **>10^4 CFU/mL** is generally considered significant for diagnosing a UTI, indicating active infection rather than contamination. - _S. saprophyticus_ accounts for 10-20% of UTIs in sexually active young women and is the second most common cause after _E. coli_. *Commensal* - While some coagulase-negative staphylococci can be commensals, **_S. saprophyticus_** is an important pathogen, especially in UTIs. - The combination of **novobiocin resistance** and a significant bacterial count in a symptomatic patient strongly points away from a commensal role. *Contamination* - **Contamination** usually involves lower bacterial counts ( 10^4 CFU/mL** of a pure culture of a known urinary pathogen (_S. saprophyticus_) in a symptomatic patient makes contamination unlikely. *Repeat culture needed* - Repeat cultures are indicated when initial results are equivocal (e.g., low counts, mixed flora, or asymptomatic bacteriuria). - For symptomatic UTI with **>10^4 CFU/mL** of a known pathogen, a single culture is sufficient for diagnosis and treatment initiation. - Multiple consecutive samples are primarily used for diagnosing **bacteremia** or **endocarditis**, not routine UTI.

Q: Which viral infection is most likely responsible for triggering this aplastic crisis in the patient?

Parvovirus B19. ***Parvovirus B19*** - **Parvovirus B19** specifically targets and destroys **red blood cell precursors** in the bone marrow, leading to a temporary cessation of erythropoiesis [1]. - In patients with underlying hemolytic anemias (e.g., **sickle cell disease**, **hereditary spherocytosis**), this temporary aplasia can trigger a severe **aplastic crisis** due to their already shortened red blood cell lifespan [2]. *Epstein-Barr Virus (EBV)* - While EBV can cause various hematologic complications, including some myelosuppression, it is not typically associated with triggering acute **aplastic crises** due to direct erythroid precursor destruction [3]. - EBV is primarily known for causing **infectious mononucleosis** and is linked to lymphoproliferative disorders [3]. *Hepatitis B Virus (HBV)* - HBV infection primarily affects the **liver** and is not a common cause of acute **aplastic crisis** by directly targeting bone marrow hematopoietic cells. - Chronic HBV infection can rarely be associated with **aplastic anemia**, but not usually with an acute crisis. *Cytomegalovirus (CMV)* - CMV can cause myelosuppression, especially in **immunocompromised individuals**, and may lead to pancytopenia. - However, CMV does not typically induce the sudden and severe **erythroid aplasia** characteristic of an aplastic crisis in hemolytic anemia patients, as seen with Parvovirus B19 [1].

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

Flagella. **Flagella** - The "H" in bacterial designations like *Escherichia coli* O157:H7 refers to the **H antigen**, which is associated with bacterial **flagella**. - Flagellar antigens are important for serotyping bacteria, identifying different strains based on their unique flagellar protein compositions. *Lipopolysaccharide (LPS)* - The "O" in bacterial designations like *E. coli* O157 refers to the **O antigen**, which is part of the **lipopolysaccharide (LPS)** layer on the outer membrane of Gram-negative bacteria. - LPS is a major component of the bacterial outer membrane and acts as an **endotoxin**. *Capsule* - The "K" in some bacterial serotypes (e.g., *Klebsiella pneumoniae* K1) refers to the **K antigen**, which is associated with the **capsule**. - The capsule is a protective layer surrounding some bacteria that helps them evade phagocytosis. *Fimbriae* - **Fimbriae** (also known as pili) are short, hair-like appendages on the surface of some bacteria that aid in **adhesion** to host cells. - While fimbriae have their own antigenic properties, they are not typically designated by the "H" prefix in standard serotyping, which specifically refers to flagellar antigens.

Question 1

A patient presents with painful vesicles as shown in the image. What is the diagnosis?

Accepted Answer

Herpes

Answer

Chancroid

Answer

Syphilis

Answer

Candidiasis

Question 2

A 40-year-old farmer presents with fever, calf tenderness, conjunctival suffusion, retro-orbital pain, and hypokalemia. What is the diagnosis?

Accepted Answer

Leptospira

Answer

Malaria

Answer

Dengue

Answer

Influenza

Answer

Typhoid fever

Question 3

A patient living with HIV presents with foulsmelling stools. Microscopic examination of the stool reveals no cysts or ova, but a 200-micrometer larva is observed. What is the most likely pathogen?

Accepted Answer

Strongyloides stercoralis

Answer

Ascaris lumbricoides

Answer

Ancylostoma duodenale

Answer

Schistosoma mansoni

Question 4

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 5

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 6

Desert rheumatism is caused by:

Accepted Answer

Coccidioides immitis

Answer

Paracoccidioides brasiliensis

Answer

Candida albicans

Answer

Cryptococcus neoformans

Question 7

Broad-based budding yeasts are seen in:

Accepted Answer

Blastomycosis

Answer

Histoplasmosis

Answer

Candidiasis

Answer

Coccidioidomycosis

Question 8

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 9

Which viral infection is most likely responsible for triggering this aplastic crisis in the patient?

Accepted Answer

Parvovirus B19

Answer

Epstein-Barr Virus (EBV)

Answer

Hepatitis B Virus (HBV)

Answer

Cytomegalovirus (CMV)

Question 10

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

NEET-PG 2024

Dermatology

Internal Medicine

Microbiology