Infectious Diseases Practice Questions

Q: What is the minimum induration measurement for a positive Tuberculin test?

>10mm. >10mm - A positive tuberculin skin test (TST) with an induration of **>10mm** is generally considered significant in the general population with no known risk factors for TB. - This cutoff helps identify individuals who have been infected with **Mycobacterium tuberculosis** and have developed a delayed-type hypersensitivity response. *>2mm* - An induration of **>2mm** is too small to be considered a positive TST result in any risk group. - Such a small reaction is typically interpreted as **negative** or non-specific. *>5mm* - An induration of **>5mm** is considered positive in specific high-risk groups, such as individuals with **HIV infection**, recent close contacts of TB cases, or those with **fibrotic changes** on chest X-ray consistent with prior TB. - It is not the general cutoff for a positive test in the broader population. *>7mm* - An induration of **>7mm** does not correspond to a standard interpretive cutoff for a positive TST in any established guideline. - It falls between the **>5mm** (high-risk) and **>10mm** (general population) criteria, making it an incorrect general threshold.

Q: Most important feature to diagnose severe pneumonia?

Chest indrawing. ***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].

Q: Which of the following conditions does not present with a rash?

Q fever. ***Q fever*** - **Q fever** is typically characterized by **fever, headache, chills, and myalgia,** but a skin rash is generally absent. - The disease is caused by *Coxiella burnetii* and can lead to pneumonia or hepatitis, without cutaneous manifestations. *Scrub typhus* - **Scrub typhus** characteristically presents with a **maculopapular rash** that may become generalized [1]. - A distinguishing feature is the presence of an **eschar** at the site of the chigger bite [1]. *Epidemic typhus* - **Epidemic typhus** often involves a **macular or maculopapular rash** that begins on the trunk and spreads peripherally, typically sparing the face, palms, and soles [1]. - This rash usually appears 4-7 days after the onset of fever [1]. *Endemic typhus* - **Endemic (murine) typhus** is also associated with a **maculopapular rash**, which tends to be less extensive and less prominent than that seen in epidemic typhus [1]. - The rash typically starts on the trunk and spreads, usually after 4-5 days of fever [1].

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

Aortic arch. ***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.

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

Quinolone. ***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.

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

Dorsolumbar. ***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.

Q: Most common symptom of genitourinary TB

Hematuria. ***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.

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

Joint aspiration for synovial fluid analysis. 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.

Q: What is the first symptom of leprosy?

Decreased pain. 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 1

What is the minimum induration measurement for a positive Tuberculin test?

Accepted Answer

>10mm

Answer

>5mm

Answer

>7mm

Answer

>2mm

Question 2

Most important feature to diagnose severe pneumonia?

Accepted Answer

Chest indrawing

Answer

Nasal flaring

Answer

Fast breathing

Answer

Cyanosis

Question 3

Which of the following conditions does not present with a rash?

Accepted Answer

Q fever

Answer

Scrub typhus

Answer

Epidemic typhus

Answer

Endemic typhus

Question 4

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

Accepted Answer

Aortic arch

Answer

Abdominal aorta (proximal to renal arteries)

Answer

Thoracic aorta (descending)

Answer

Abdominal aorta (distal to renal arteries)

Question 5

Which of the following statements about lepromatous leprosy is true?

Accepted Answer

Lepromatous leprosy typically presents with multiple cutaneous lesions.

Answer

Thickened peripheral nerves are a common feature.

Answer

Erythema nodosum leprosum occurs in less than 50% of cases.

Answer

The lepromin test is usually negative or weakly positive.

Question 6

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

Accepted Answer

Quinolone

Answer

Doxycycline

Answer

Artesunate

Answer

Quinine

Question 7

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

Accepted Answer

Dorsolumbar

Answer

Sacral

Answer

Lumbosacral

Answer

Cervical

Question 8

Most common symptom of genitourinary TB

Accepted Answer

Hematuria

Answer

Increased frequency

Answer

Renal colic

Answer

Painful micturition

Question 9

What is the most reliable method for diagnosing septic arthritis?

Accepted Answer

Joint aspiration for synovial fluid analysis

Answer

X-ray imaging to detect joint abnormalities

Answer

Ultrasound (USG) imaging to detect effusion

Answer

MRI for detailed joint imaging

Question 10

What is the first symptom of leprosy?

Accepted Answer

Decreased pain

Answer

Decreased vibration & position sense

Answer

Decreased temperature

Answer

Decreased light touch

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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