Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1231: Most important feature to diagnose severe pneumonia?

A. Nasal flaring
B. Fast breathing
C. Cyanosis
D. Chest indrawing (Correct Answer)

Explanation: ***Chest indrawing*** - **Chest indrawing** is a critical sign of severe respiratory distress in pneumonia, indicating increased effort needed for breathing as the body attempts to draw in more air. - This symptom suggests that the affected individual's respiratory muscles are working harder than normal to overcome airway obstruction or reduced lung compliance, often leading to **hypoxia**. *Cyanosis* - While a serious sign of **hypoxemia**, **cyanosis** is often a late manifestation and not visible until oxygen saturation drops significantly. - It indicates advanced **respiratory failure** and may not be the earliest or most sensitive indicator of severe pneumonia. *Nasal flaring* - **Nasal flaring** is a sign of increased respiratory effort seen more commonly in infants and young children. - While it indicates **respiratory distress**, it is less specific for the severity of pneumonia compared to chest indrawing, which suggests more pronounced ventilatory compromise. *Fast breathing* - **Fast breathing** (tachypnea) is a common sign of pneumonia across all severities, as the body tries to compensate for reduced oxygen exchange. - However, it is not specific enough on its own to diagnose **severe pneumonia**, and other signs of increased respiratory effort like chest indrawing are needed to indicate severe disease [1].

Question 1232: Which of the following characteristics can be used to differentiate the rash of chickenpox from the rash of smallpox?

A. Deep-seated
B. Pleomorphic (Correct Answer)
C. Centrifugal
D. Multilocular

Explanation: ***Pleomorphic*** - The rash of **chickenpox** is **pleomorphic**, meaning lesions at various stages of development (macules, papules, vesicles, scabs) are present simultaneously in the same body area. - In contrast, a **smallpox** rash is **monomorphic**, with all lesions in a given area appearing at the same stage of development. *Centrifugal* - A **centrifugal distribution** (lesions more concentrated on the face and extremities) is characteristic of **smallpox**. - **Chickenpox** typically has a **centripetal distribution**, with lesions more concentrated on the trunk. *Deep-seated* - **Smallpox** lesions are described as **deep-seated** and feel like "shot under the skin," often associated with significant scarring. - **Chickenpox** lesions are superficial and less likely to cause scarring unless secondarily infected. *Multilocular* - **Smallpox** vesicles and pustules are typically **multilocular**, meaning they have internal septations and do not collapse when punctured. - **Chickenpox** vesicles are unilocular, appearing as a single compartment, and collapse when punctured.

Question 1233: Which of the following symptoms is commonly associated with giardiasis?

A. Steatorrhea and flatulence (Correct Answer)
B. All of the options
C. Nausea and vomiting
D. Abdominal pain

Explanation: ***Steatorrhea and flatulence*** - **Giardiasis** is an intestinal infection caused by the parasite *Giardia lamblia*, leading to malabsorption and characteristic symptoms [1]. - The parasite attaches to the intestinal lining, interfering with fat absorption, which results in **steatorrhea** (fatty, foul-smelling stools) and increased gas production causing **flatulence** [1]. *Nausea and vomiting* - While **nausea** can occur in giardiasis, **vomiting** is less common as a primary or dominant symptom. - These symptoms are more characteristic of other gastrointestinal infections like **viral gastroenteritis**. *Abdominal pain* - **Abdominal pain** is a general symptom that can occur with many gastrointestinal issues, including giardiasis [1]. - However, it's not as specific or as clinically defining for giardiasis as **steatorrhea** and **flatulence**, which are direct consequences of the parasite's impact on fat absorption. *All of the options* - Although some patients with giardiasis may experience nausea and abdominal pain, **steatorrhea** and **flatulence** are the most direct and specific indicators of the malabsorption caused by *Giardia lamblia* [1]. - Choosing "all of the above" would imply that all listed symptoms are equally common and specific, which is not the case for giardiasis.

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: 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.

Question 1236: Tuberculosis of the spine; what is the most common site affected?

A. Sacral
B. Dorsolumbar (Correct Answer)
C. Lumbosacral
D. Cervical

Explanation: ***94ed055d-c7da-4d18-a2fd-52720dfe8b6e*** - The **dorsolumbar (thoracolumbar)** region is the most common site of **spinal tuberculosis (Pott's disease)** [1] due to its high vascularity, facilitating hematogenous spread. - **Spinal tuberculosis** typically affects the vertebral bodies, leading to their destruction, kyphosis (angular deformity), and potentially neurological deficits [1]. *aebdfe6c-98dc-4073-892f-bb24d047bab4* - The **sacral** region can be affected by **tuberculosis**, but it is considerably less common than the thoracolumbar region. - Involvement of the sacrum is often associated with **direct extension** from adjacent structures, such as the sacroiliac joint, rather than primary vertebral involvement. *15c1feef-e3ca-496f-a180-127d52b77bfa* - **Cervical spine tuberculosis** is relatively rare, accounting for a small percentage of all spinal tuberculosis cases. - While possible, it presents with specific challenges due to the proximity of vital neurological and vascular structures. *d05d4d13-bb83-4f26-aa2d-c9c0203d299c* - The **lumbosacral region** (L5-S1) can be involved in **tuberculosis**, but it is less frequently affected than the thoracolumbar region. - While the lumbar spine is a common site, the entire lumbosacral region as a single entity is not the most common spot for spinal TB.

Question 1237: 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 1238: 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 1239: 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 1240: 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.

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Principles of Antimicrobial Therapy

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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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