Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1231: Which of the following is true about Hepatitis A virus?

A. Causes chronic hepatitis
B. Helps HDV replication
C. Causes cirrhosis
D. Common cause of hepatitis in children (Correct Answer)

Explanation: ***Common cause of hepatitis in children*** - **Hepatitis A virus (HAV)** infection is often acquired in childhood, particularly in areas with poor sanitation, and many infections are **asymptomatic** or mild in children [1]. - Due to their developing immune systems and often exposure in daycare or school settings, children are a highly susceptible population for HAV transmission [1]. *Causes cirrhosis* - **HAV infection** is an **acute self-limiting illness** and typically does not lead to chronic liver disease or cirrhosis [1]. - **Cirrhosis** is primarily associated with chronic viral hepatitis (e.g., HBV, HCV), alcohol-related liver disease, or certain autoimmune conditions. *Helps HDV replication* - **Hepatitis D virus (HDV)** is a **defective virus** that requires the presence of **Hepatitis B virus (HBV)** surface antigen (HBsAg) for its replication and assembly [1]. - **HAV** has no role in the replication or pathogenesis of **HDV** [1]. *Causes chronic hepatitis* - **HAV infection** results in an **acute inflammatory response** in the liver that resolves spontaneously in most cases [1]. - Unlike **HBV** and **HCV**, **HAV** does not establish a persistent infection and, therefore, does not cause chronic hepatitis [1].

Question 1232: 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.

Question 1233: Which of the following statements about polio is false?

A. 99% non paralytic
B. Aseptic meningitis
C. Flaccid paralysis
D. Increased tendon reflexes (Correct Answer)

Explanation: ***Increased tendon reflexes*** - Polio causes **lower motor neuron damage**, specifically to the anterior horn cells of the spinal cord [1]. - This damage leads to **flaccid paralysis** and **decreased or absent deep tendon reflexes**, not increased reflexes [3]. *99% non paralytic* - The vast majority of poliovirus infections (approximately 95-99%) are **asymptomatic** or cause only mild, non-specific symptoms. - Only a small percentage of infected individuals develop the more severe paralytic form of the disease. *Flaccid paralysis* - Poliovirus directly attacks and destroys **motor neurons** in the anterior horn of the spinal cord [1]. - This damage results in **muscle weakness** and loss of muscle tone, leading to **flaccid paralysis** [3]. *Aseptic meningitis* - About 1-5% of poliovirus infections can manifest as **aseptic meningitis**, characterized by symptoms like fever, headache, neck stiffness, and vomiting without bacterial infection [2]. - This form of meningitis is typically **self-limiting** and does not lead to paralysis [2].

Question 1234: Which part of the aorta is most commonly involved in syphilitic aneurysms?

A. Abdominal aorta (proximal to renal arteries)
B. Aortic arch (Correct Answer)
C. Thoracic aorta (descending)
D. Abdominal aorta (distal to renal arteries)

Explanation: ***Aortic arch*** - Syphilitic aneurysms typically result from **tertiary syphilis**, which causes **vasa vasorum endarteritis** in the aorta, leading to weakened vessel walls. - The **aortic arch** is most frequently affected due to its rich supply of vasa vasorum, predisposing it to damage in this stage of the disease. *Thoracic aorta (descending)* - While other parts of the thoracic aorta can be affected, the **descending thoracic aorta** is less commonly involved in syphilitic aneurysms compared to the aortic arch or ascending aorta. - Aneurysms in this segment are more often associated with **atherosclerosis** rather than syphilis. *Abdominal aorta (proximal to renal arteries)* - Aneurysms of the **abdominal aorta** are overwhelmingly due to **atherosclerosis**, not syphilis [1]. - These are typically located distal to the renal arteries and are less associated with the characteristic inflammatory changes seen in syphilis. *Abdominal aorta (distal to renal arteries)* - The vast majority of **abdominal aortic aneurysms (AAAs)** occur in the segment **distal to the renal arteries** and are primarily caused by **atherosclerosis** [1]. - **Syphilitic aneurysms** rarely affect the abdominal aorta, as the vasa vasorum supply, and thus the inflammatory process, predominantly targets the proximal great vessels.

Question 1235: What is the most reliable method for diagnosing septic arthritis?

A. X-ray imaging to detect joint abnormalities
B. Ultrasound (USG) imaging to detect effusion
C. MRI for detailed joint imaging
D. Joint aspiration for synovial fluid analysis (Correct Answer)

Explanation: Direct examination of the **synovial fluid** is crucial for identifying the causative organism and confirming septic arthritis [1]. Key diagnostic features from synovial fluid include **leukocyte count** (usually >50,000 cells/mm³ with >75% neutrophils), **Gram stain** for bacteria, and **culture** for definitive organism identification. Joint aspiration should be performed as part of emergency management, often using a large-bore needle [1]. *X-ray imaging to detect joint abnormalities* - X-rays may show **joint effusions** or **soft tissue swelling** in early septic arthritis, but these are nonspecific findings. - **Bony erosions** or **joint space narrowing** typically appear only in **later stages** of the disease and are not diagnostic early on [2]. *Ultrasound (USG) imaging to detect effusion* - Ultrasound is effective for detecting and guiding aspiration of **joint effusions**, which are common in septic arthritis. - However, it does not confirm the **presence of infection** or identify the **causative agent**, making it a supportive, not primary diagnostic, tool. *MRI for detailed joint imaging* - MRI offers detailed imaging of **soft tissues**, cartilage, and bone, and can show **synovial enhancement**, **bone marrow edema**, and early **cartilage destruction** in septic arthritis. - While sensitive, MRI is **expensive** and **time-consuming**, and ultimately does not provide **microbiological confirmation**, which is essential for definitive diagnosis and treatment.

Question 1236: Which of the following medications is not typically used in the treatment of malignant malaria?

A. Doxycycline
B. Artesunate
C. Quinine
D. Quinolone (Correct Answer)

Explanation: ***Quinolone*** - **Quinolone** antibiotics, while broad-spectrum, are not typically used as primary antimalarial agents due to limited efficacy against *Plasmodium falciparum* and potential for resistance. - Their use in malaria treatment is generally restricted to specific co-infections rather than direct antimalarial efficacy. *Quinine* - **Quinine** has been a cornerstone of severe malaria treatment for many years, especially in regions with limited access to newer artemisinin derivatives. - It works by interfering with the parasite's ability to detoxify heme, thus killing the parasites. *Doxycycline* - **Doxycycline** is an effective antimalarial, particularly as a prophylactic agent and in combination therapy for uncomplicated malaria or as an alternative for severe malaria when other agents are contraindicated. - It inhibits **protein synthesis** in the parasite. *Artesunate* - **Artesunate** is the recommended first-line treatment for severe malaria due to its rapid action and potent parasiticidal effects. - It is an **artemisinin derivative** that produces free radicals toxic to the parasite.

Question 1237: What is the first symptom of leprosy?

A. Decreased vibration & position sense
B. Decreased pain (Correct Answer)
C. Decreased temperature
D. Decreased light touch

Explanation: Decreased pain - Leprosy primarily targets Schwann cells in peripheral nerves, leading to sensory loss [1]. - The sensation of pain is typically affected earliest, often presenting as areas of numbness [1]. Decreased vibration & position sense - These sensations are typically carried by larger myelinated fibers, which tend to be affected later in the disease progression of leprosy. - While eventually involved, they are not usually the first symptom of sensory loss. Decreased temperature - Temperature sensation is also an early modality affected in leprosy, as it's carried by small, unmyelinated or thinly myelinated fibers [1]. - However, pain is often cited as the very first sensory loss, even preceding temperature changes in some cases. Decreased light touch - Light touch sensation is generally an early loss, similar to pain and temperature, due to damage to nerve fibers in the skin. - But, when distinguishing the absolute first symptom, pain perception often shows impairment even before light touch in affected areas.

Question 1238: Most common symptom of genitourinary TB

A. Increased frequency
B. Renal colic
C. Painful micturition
D. Hematuria (Correct Answer)

Explanation: ***Hematuria*** - **Gross or microscopic hematuria** is the most common symptom of genitourinary tuberculosis, often occurring early in the disease course. - It results from the **inflammatory and destructive changes** caused by Mycobacterium tuberculosis in the urinary tract. *Renal colic* - Renal colic is typically associated with **acute obstruction of the ureter**, often by a renal stone. - While TB can cause strictures leading to obstruction, **colic** itself is not the most common initial symptom. *Increased frequency* - Increased urinary frequency is a common symptom in genitourinary TB, especially with **bladder involvement**. - However, it ranks below hematuria in terms of overall prevalence as the *most common* symptom. *Painful micturition* - **Dysuria** or painful micturition is frequently observed in genitourinary TB, particularly with **bladder or urethral inflammation**. - While common, it is generally less prevalent than hematuria as the presenting complaint.

Question 1239: Which of the following is NOT a common pathogen causing pneumonia in COPD patients?

A. Klebsiella pneumoniae
B. Legionella spp (Correct Answer)
C. Pseudomonas aeruginosa
D. Haemophilus influenzae

Explanation: ***Legionella spp*** - While *Legionella* can cause pneumonia, it is **not a common pathogen** specifically in COPD exacerbations or community-acquired pneumonia in these patients [1]. - *Legionella* pneumonia often presents with **extrapulmonary symptoms** like diarrhea and hyponatremia and is typically associated with contaminated water sources [1]. *Haemophilus influenzae* - This is a very common pathogen causing both **acute exacerbations of COPD (AECOPD)** and pneumonia in patients with underlying COPD [1]. - COPD patients often have **impaired mucociliary clearance** and altered airway microbiology, making them susceptible to *H. influenzae* colonization and infection [1]. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is an important pathogen in **severe COPD exacerbations**, especially in patients with frequent exacerbations, bronchiectasis, or prior antibiotic use. - Its presence often indicates a **more severe disease course** and requires specific antibiotic coverage. *Klebsiella pneumoniae* - *Klebsiella pneumoniae* is a significant cause of **pneumonia in immunocompromised individuals**, including those with COPD, diabetes, or alcoholism. - It often leads to **severe, necrotizing pneumonia**, particularly in the upper lobes, and can cause abscess formation.

Question 1240: Which of the following statements about lepromatous leprosy is true?

A. Thickened peripheral nerves are a common feature.
B. Erythema nodosum leprosum occurs in less than 50% of cases.
C. The lepromin test is usually negative or weakly positive.
D. Lepromatous leprosy typically presents with multiple cutaneous lesions. (Correct Answer)

Explanation: ***Lepromatous leprosy typically presents with multiple cutaneous lesions.*** - Lepromatous leprosy is characterized by **widespread skin involvement**, often manifesting as numerous, symmetrically distributed nodules, plaques, and macules [1]. - The high bacterial load in lepromatous leprosy leads to extensive skin infiltration due to the host's ineffective cellular immune response. *Thickened peripheral nerves are a common feature.* - While nerve thickening can occur in lepromatous leprosy, it is a **more prominent and early feature** of **tuberculoid leprosy** due to a more robust granulomatous inflammatory response within the nerve [2]. - In lepromatous leprosy, nerve damage is often more diffuse and less demarcated, leading to **insidious nerve loss** rather than clearly palpable thickening. *Erythema nodosum leprosum occurs in less than 50% of cases.* - **Erythema nodosum leprosum (ENL)** is a common type 2 leprosy reaction associated with lepromatous leprosy, estimated to occur in **approximately 30-50% of untreated patients** [1]. - It results from an immune complex deposition and is triggered by changes in bacillary load or drug therapy, and it is observed within the stated percentage range. *The lepromin test is usually negative or weakly positive.* - The lepromin test assesses **cell-mediated immunity** to *Mycobacterium leprae* antigens. - In lepromatous leprosy patients, there is a **deficient cell-mediated immune response**, making the lepromin test typically **negative**, indicating anergy.

Practice by Chapter

Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

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HIV/AIDS and Related Infections

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Tuberculosis and Mycobacterial Diseases

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Tropical and Parasitic Infections

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Viral Infections (Hepatitis, Herpes, etc.)

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Healthcare-Associated Infections

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Fungal Infections

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Sepsis and Septic Shock

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Infection in Immunocompromised Hosts

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Emerging and Re-emerging Infections

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Antimicrobial Resistance

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Vaccination Principles

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