Internal Medicine
2 questionsPseudomembranous colitis, all are true except:
Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 551: Pseudomembranous colitis, all are true except:
- A. Blood in stools is a common feature (Correct Answer)
- B. Toxin A is responsible for clinical manifestation
- C. Summit lesions are early histopathological findings
- D. Toxin B is responsible for clinical manifestation
Explanation: ***Blood in stools is a common feature*** - While diarrhea is a hallmark of **pseudomembranous colitis**, **bloody stools** are uncommon and, if present, suggest severe disease or an alternative diagnosis [1]. - The typical presentation involves **watery diarrhea**, abdominal cramps, and fever, not usually overt bleeding [1]. *Toxin A is responsible for clinical manifestation* - **Toxin A (TcdA)** is one of the primary exotoxins produced by *Clostridioides difficile* and contributes significantly to the **inflammation** and fluid secretion seen in pseudomembranous colitis. - It acts as an **enterotoxin**, causing fluid secretion and mucosal damage in the colon [1]. *Summit lesions are early histopathological findings* - **Summit lesions**, also known as "summit pseudomembranes" or **"volcano lesions"**, refer to characteristic histological findings where inflammatory exudates effuse from the tips of damaged crypts. - These are typical early findings in pseudomembranous colitis, demonstrating the focal nature of the **mucosal injury**. *Toxin B is responsible for clinical manifestation* - **Toxin B (TcdB)** is another key exotoxin produced by *Clostridioides difficile*, and it is considered even more **cytotoxic** than Toxin A [1]. - It causes significant **cell damage** and **apoptosis**, playing a crucial role in the development of the pseudomembranes and clinical symptoms [1].
Question 552: Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?
- A. Meningitis
- B. Otic polypoid mass (Correct Answer)
- C. Pneumonia
- D. Ophthalmic choroid lesion
Explanation: ***Otic polypoid mass*** - While *Pneumocystis jirovecii* (formerly *carinii*) can cause **extrapulmonary disease** in immunocompromised patients, an **otic polypoid mass** is an extremely rare and atypical presentation. - Extrapulmonary manifestations usually involve organs with rich vascular supply, but ear involvement in this form is not a characteristic feature. *Pneumonia* - **Pneumocystis pneumonia (PCP)** is the **most common opportunistic infection** and AIDS-defining illness caused by *Pneumocystis jirovecii* in individuals with AIDS [1]. - It typically manifests as **fever, cough, and dyspnea** with characteristic imaging findings [1]. *Ophthalmic choroid lesion* - **Choroid lesions** due to *Pneumocystis jirovecii* are a recognized, albeit less common, **extrapulmonary manifestation** in immunocompromised patients, particularly those with AIDS. - These lesions are usually **asymptomatic** and discovered incidentally on funduscopic examination. *Meningitis* - Although *Pneumocystis jirovecii* causing **meningitis** is rare, it has been reported in severely immunocompromised individuals with AIDS, often as part of disseminated disease. - Central nervous system involvement signifies **widespread dissemination** and advanced immunosuppression.
Microbiology
7 questionsWhich gene of Hepatitis B virus (HBV) is most commonly associated with mutations causing antiviral drug resistance?
Which of the following statements about malaria transmission is correct?
Amoebic liver abscess can be diagnosed by demonstrating-
Who discovered the bacterium Treponema pallidum?
Who discovered the bacterium Mycobacterium tuberculosis, which causes tuberculosis?
Which of the following bacteria does not exhibit bipolar staining?
Which of the following bacteria is not capsulated?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 551: Which gene of Hepatitis B virus (HBV) is most commonly associated with mutations causing antiviral drug resistance?
- A. X gene
- B. S gene
- C. C gene
- D. P gene (Correct Answer)
Explanation: ***P gene*** - The **P gene** (polymerase gene) of HBV encodes the viral reverse transcriptase which is essential for viral replication. - Mutations in the P gene can lead to **antiviral drug resistance**, particularly to nucleos(t)ide analogues. *X gene* - The **X gene** encodes the X protein (HBx), a **transcriptional transactivator** involved in viral replication and pathogenesis. - While important for viral function, it is not the primary target for antiviral therapy, and mutations are less frequently associated with drug resistance. *S gene* - The **S gene** encodes the **surface antigens (HBsAg)**, which are crucial for viral entry and immune evasion. - Mutations in the S gene can lead to **vaccine escape mutants** or alter HBsAg detection, but not directly responsible for antiviral resistance. *C gene* - The **C gene** encodes the **core protein (HBcAg)** and the precore protein (HBeAg). - These proteins are involved in **viral particle assembly** and immune modulation, but mutations in this gene are not typically associated with resistance to antiviral drugs.
Question 552: Which of the following statements about malaria transmission is correct?
- A. Individuals harboring gametocytes can transmit malaria. (Correct Answer)
- B. P. vivax always completely fills the infected RBC with schizonts.
- C. Malaria can only be transmitted through blood transfusions.
- D. All stages of P. falciparum are commonly seen in peripheral blood smears.
Explanation: ***Individuals harboring gametocytes can transmit malaria.*** - **Gametocytes** are the sexual stage of the malaria parasite that circulate in the human bloodstream and are infectious to mosquitos. - When an *Anopheles* mosquito feeds on an infected human, it ingests these gametocytes, allowing the parasite's life cycle to continue in the mosquito vector, leading to transmission. *P. vivax always completely fills the infected RBC with schizonts.* - While *P. vivax* does infect **reticulocytes** (young RBCs) and can enlarge them, the **schizonts** typically occupy a significant portion but not always completely fill the host cell. - The infected RBCs are often enlarged to about 1.5 to 2 times their normal size and contain numerous **Schüffner's dots**. *Malaria can only be transmitted through blood transfusions.* - The primary mode of malaria transmission is through the bite of an **infected female *Anopheles* mosquito**. - While **blood transfusions** can transmit malaria, it is a less common and secondary route compared to vector-borne transmission. *All stages of P. falciparum are commonly seen in peripheral blood smears.* - In *P. falciparum* infections, only the **ring forms** and **gametocytes** are commonly observed in the peripheral blood smear. - The more mature asexual stages (trophozoites and schizonts) typically sequester in the capillaries of internal organs, where they are not readily visible in peripheral circulation.
Question 553: Amoebic liver abscess can be diagnosed by demonstrating-
- A. Trophozoites in the pus (Correct Answer)
- B. Trophozoites in the feces
- C. Cysts in the pus
- D. Cysts in the liver
Explanation: ***Trophozoites in the pus*** - **Amoebic liver abscesses** are caused by the invasive **trophozoite stage** of *Entamoeba histolytica*. - Demonstrating **trophozoites** in the characteristic **'anchovy paste' pus** aspirated from the abscess cavity is diagnostic. *Cysts in the pus* - **Cysts** are the **infective stage** of *Entamoeba histolytica* and are typically found in the **feces**, not in an abscess. - Cysts are responsible for transmission and survival outside the host, but they do not cause invasive disease. *Cysts in the liver* - The disease in the liver is caused by **trophozoites**, which invade the intestinal wall and then spread to the liver. - **Cysts** are never found within the liver parenchyma or abscesses. *Trophozoites in the feces* - While **trophozoites** can be found in the feces during acute amoebic dysentery, their presence alone does not confirm a liver abscess. - Furthermore, **trophozoites** are fragile and often difficult to detect in stool samples, especially once the stool has cooled.
Question 554: Who discovered the bacterium Treponema pallidum?
- A. Robert Koch
- B. Twort
- C. Ellerman
- D. Fritz Schaudinn and Erich Hoffmann (Correct Answer)
Explanation: ***Fritz Schaudinn and Erich Hoffmann*** - **Fritz Schaudinn** was a German zoologist, and **Erich Hoffmann** was a German dermatologist; they jointly discovered **Treponema pallidum** in **1905**. - Their discovery of the spirochete was a crucial step in understanding the etiology of **syphilis**. *Robert Koch* - **Robert Koch** is renowned for identifying the causative agents of **tuberculosis**, **cholera**, and **anthrax**. - He developed Koch's postulates, a fundamental set of criteria for establishing the causal relationship between a microbe and a disease. *Twort* - **Frederick Twort** was a British bacteriologist who is credited with the discovery of **bacteriophages** in **1915**. - His work involved examining transparent areas in bacterial cultures, leading to the identification of lytic viruses that infect bacteria. *Ellerman* - **Vilhelm Ellerman** was a Danish pathologist known for his work in **hematology** and **virology**. - Alongside **Olaf Bang**, he demonstrated that avian leukemia (erythroleukemia) could be transmitted by a filterable agent, indicating a viral etiology for some cancers.
Question 555: Who discovered the bacterium Mycobacterium tuberculosis, which causes tuberculosis?
- A. Jenner
- B. Louis Pasteur
- C. Robert Koch (Correct Answer)
- D. Lister
Explanation: ***Robert Koch*** - **Robert Koch** discovered the bacterium *Mycobacterium tuberculosis* in **1882**, identifying its role as the causative agent of tuberculosis. - His work was crucial in establishing the germ theory of disease and earned him the Nobel Prize in Physiology or Medicine in 1905. *Louis Pasteur* - **Louis Pasteur** was a pioneer in microbiology, known for his work on **pasteurization**, **vaccinations** (e.g., rabies and anthrax), and disproving spontaneous generation. - While he made significant contributions to understanding infectious diseases, he did not discover *Mycobacterium tuberculosis*. *Lister* - **Joseph Lister** was a British surgeon who revolutionized surgery by introducing **antiseptic techniques** using carbolic acid to prevent infections. - His contributions were fundamental to reducing mortality rates from surgical infections, but he did not discover the tuberculosis bacterium. *Jenner* - **Edward Jenner** is famous for developing the **smallpox vaccine**, which was a groundbreaking achievement in immunology and public health. - His work, though vital for preventing infectious diseases, predates and is unrelated to the discovery of *Mycobacterium tuberculosis*.
Question 556: Which of the following bacteria does not exhibit bipolar staining?
- A. Haemophilus influenzae (Correct Answer)
- B. Yersinia pestis
- C. Calymmatobacterium granulomatis
- D. Francisella tularensis
Explanation: ***Haemophilus influenzae*** - *Haemophilus influenzae* is a **pleomorphic coccobacillus** that typically stains uniformly and does not exhibit characteristic **bipolar staining**. - Its presence is often identified by Gram stain showing small, Gram-negative rods, but without the distinctive safety pin appearance. *Calymmatobacterium granulomatis* - *Calymmatobacterium granulomatis* (now *Klebsiella granulomatis*) is known to exhibit **bipolar staining**, often described as a **"safety pin" appearance**, especially in tissue smears from granuloma inguinale lesions. - This characteristic staining is due to the concentration of stain at the ends of the rod-shaped bacteria. *Yersinia pestis* - *Yersinia pestis*, the causative agent of plague, is classically described as having **bipolar staining**, giving it a distinctive **"safety pin" appearance** under a microscope. - This finding is a key diagnostic feature, particularly when observed in Gram-stained smears of clinical samples. *Francisella tularensis* - *Francisella tularensis* is a small, Gram-negative coccobacillus that is known to exhibit **bipolar staining**, though it may be less prominent than in *Yersinia pestis*. - This characteristic can assist in the microscopic identification of the bacterium, which causes tularemia.
Question 557: Which of the following bacteria is not capsulated?
- A. Pneumococcus
- B. Klebsiella
- C. Meningococcus
- D. Proteus (Correct Answer)
Explanation: ***Proteus*** - *Proteus* species are **non-capsulated bacteria**; their primary virulence factor is urease production and motility via flagella. - While they can cause infections, the lack of a capsule means they do not evade phagocytosis in the same manner as the other listed options. *Pneumococcus* - **_Streptococcus pneumoniae_**, commonly known as pneumococcus, is a highly **capsulated bacterium**. - Its polysaccharide capsule is a major **virulence factor** that inhibits phagocytosis, contributing to its ability to cause pneumonia, meningitis, and other invasive diseases. *Klebsiella* - **_Klebsiella pneumoniae_** is a **heavily capsulated Gram-negative bacterium** with a prominent polysaccharide capsule. - The thick capsule gives colonies a **mucoid appearance** and serves as a major **virulence factor** that protects against phagocytosis, contributing to pneumonia, UTIs, and other infections. *Meningococcus* - **_Neisseria meningitidis_**, or meningococcus, is a **capsulated bacterium**. - Its **polysaccharide capsule** is vital for immune evasion and is the basis for serogrouping and vaccine development against meningococcal disease.
Pathology
1 questionsThe most common subtype of Non-Hodgkin's lymphoma in India is:
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 551: The most common subtype of Non-Hodgkin's lymphoma in India is:
- A. Diffuse small cell lymphocytic lymphoma
- B. Diffuse large B cell lymphoma (Correct Answer)
- C. Follicular lymphoma
- D. Burkitt's lymphoma
Explanation: ***Diffuse large B cell lymphoma*** - It is the most common subtype of **Non-Hodgkin's lymphoma** observed in India, reflecting a higher prevalence in the population. - Characterized by **aggressive clinical behavior** [1] and typically presents as a rapidly enlarging mass, often involving lymph nodes or extranodal sites. *Burkitt's lymphoma* - This subtype is known for its **high proliferation rate** and is more common in specific demographics, such as children and immunocompromised individuals. - It typically presents with **jaw lesions** or abdominal masses, which is not typical in the broader Indian population. *Diffuse small cell lymphocytic lymphoma* - More accurately classified as **chronic lymphocytic leukemia** (CLL), it is not the most common subtype of Non-Hodgkin's lymphoma. - Characterized by a **milder clinical course** and presents with lymphocytosis in peripheral blood, lacking aggressive features. *Follicular lymphoma* - This is usually a **low-grade lymphoma** associated with **indolent behavior** and may not be the most commonly diagnosed subtype in India. - It typically involves multiple lymph nodes and is characterized by **nodular patterns on histology**, making it less prevalent than diffuse large B cell lymphoma. Follicular lymphoma is rare in Asian populations [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 563-564. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 602-604.