Infectious Diseases Practice Questions

Q: Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?

Otic polypoid mass. ***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.

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: 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 is NOT a common pathogen causing pneumonia in COPD patients?

Legionella spp. ***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.

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: 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: Which species of malaria is associated with nephrotic syndrome?

P. malariae. ***P. malariae*** - *P. malariae* infection is classically associated with **quartan fever** and can lead to **nephrotic syndrome**, particularly in children [1]. - The mechanism involves the deposition of immune complexes in the glomeruli, causing **membranoproliferative glomerulonephritis**. *P. vivax* - *P. vivax* is known for causing **benign tertian malaria** and frequently leads to **relapses** due to hypnozoites in the liver [1]. - While it can cause renal dysfunction, **nephrotic syndrome** is not a characteristic complication. *P. falciparum* - *P. falciparum* is responsible for the most severe form of malaria, often complicated by **cerebral malaria**, **acute renal failure**, and **blackwater fever** [1]. - Renal complications typically present as **acute tubular necrosis** rather than nephrotic syndrome. *P. ovale* - *P. ovale* causes **mild tertian malaria** similar to *P. vivax* and is also known for **relapses** due to hypnozoites [1]. - It is the least common form of malaria and is not typically associated with **nephrotic syndrome**.

Q: HIV post exposure prophylaxis should be started within?

72 hrs. ***72 hrs*** - **Post-exposure prophylaxis (PEP)** aims to prevent HIV infection after potential exposure and should ideally be initiated as soon as possible, but no later than **72 hours** after exposure [1]. - Starting PEP within this window significantly increases its effectiveness in preventing HIV seroconversion. *1-2 hrs* - While initiating PEP as soon as possible is crucial, stating it must be within **1-2 hours** can be misleading as the window of effectiveness extends beyond this. - This timeframe might be an ideal, but not the absolute crucial limit for efficacy. *14 hrs* - This timeframe is **too restrictive** for the recommended window for PEP initiation. - Missing the opportunity within **14 hours** does not negate the effectiveness of PEP if started within the broader 72-hour window. *18 hrs* - Similar to **14 hours**, **18 hours** is an unnecessarily strict limit for PEP initiation. - Guidelines universally support starting PEP up to **72 hours** post-exposure for optimal benefit [1].

Q: Tabes dorsalis is seen in -

Tertiary syphilis. ***Tertiary syphilis*** - **Tabes dorsalis** is a neurological manifestation of **tertiary syphilis**, characterized by demyelination and degeneration of the posterior columns of the spinal cord [1]. - This leads to symptoms such as **ataxia**, **loss of proprioception**, **lightning pains**, and **Argyll-Robertson pupils**. *Primary syphilis* - Characterized by the presence of a **chancre**, a painless ulcer, at the site of infection [1]. - This stage typically occurs 3-90 days after exposure and is not associated with neurological complications of tabes dorsalis. *Latent syphilis* - This is a period during which there are **no clinical signs or symptoms** of syphilis, although the infection persists. - It can be early or late, but it is not the stage where overt neurological complications like tabes dorsalis arise [1]. *Secondary syphilis* - This stage typically presents with a **generalized mucocutaneous rash**, **lymphadenopathy**, and **condylomata lata** [1]. - While it can involve various organ systems, it does not typically include the severe neurological degeneration seen in tabes dorsalis.

Q: Meningitis with rash is seen in -

Neisseria meningitidis. **Neisseria meningitidis** - **Meningococcal meningitis** is classically associated with an acute onset of fever, headache, stiff neck, and a characteristic **petechial or purpuric rash** [1]. - The rash is due to widespread **vasculitis** and disseminated intravascular coagulation (DIC) caused by the bacteria. *H. influenzae* - While *H. influenzae* type b (Hib) was a major cause of bacterial meningitis before vaccination, it typically does not cause a *rash*. - Meningitis caused by *H. influenzae* presents with fever, headache, stiff neck, and altered mental status without dermatological manifestations. *Strepto. agalactiae* - *Streptococcus agalactiae* (Group B Strep) is a common cause of meningitis in **neonates** and infants. - It usually presents with non-specific symptoms like fever, lethargy, and poor feeding, and a rash is not a typical feature of GBS meningitis. *Pneumococcus* - *Streptococcus pneumoniae* (Pneumococcus) is another leading cause of bacterial meningitis in adults and children [1]. - Symptoms include fever, headache, stiff neck, and altered mental status, but a cutaneous rash is not characteristic of pneumococcal meningitis [1].

Question 1

Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?

Accepted Answer

Otic polypoid mass

Answer

Meningitis

Answer

Pneumonia

Answer

Ophthalmic choroid lesion

Question 2

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

Accepted Answer

>10mm

Answer

>5mm

Answer

>7mm

Answer

>2mm

Question 3

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 4

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

Accepted Answer

Legionella spp

Answer

Klebsiella pneumoniae

Answer

Pseudomonas aeruginosa

Answer

Haemophilus influenzae

Question 5

Most common symptom of genitourinary TB

Accepted Answer

Hematuria

Answer

Increased frequency

Answer

Renal colic

Answer

Painful micturition

Question 6

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

Accepted Answer

Dorsolumbar

Answer

Sacral

Answer

Lumbosacral

Answer

Cervical

Question 7

Which species of malaria is associated with nephrotic syndrome?

Accepted Answer

P. malariae

Answer

P. vivax

Answer

P. falciparum

Answer

P. ovale

Question 8

HIV post exposure prophylaxis should be started within?

Accepted Answer

72 hrs

Answer

1-2 hrs

Answer

14 hrs

Answer

18 hrs

Question 9

Tabes dorsalis is seen in -

Accepted Answer

Tertiary syphilis

Answer

Primary syphilis

Answer

Latent syphilis

Answer

Secondary syphilis

Question 10

Meningitis with rash is seen in -

Accepted Answer

Neisseria meningitidis

Answer

H. influenzae

Answer

Strepto. agalactae

Answer

Pneumococcus

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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