Infectious Diseases Practice Questions

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: 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].

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: Which type of malaria is most commonly associated with renal failure?

Falciparum. ***Falciparum*** - **Plasmodium falciparum** is notorious for its ability to cause severe and complicated malaria, including **renal failure** due to its high parasitic biomass and tendency to block microvasculature [1]. - The parasite causes red blood cells to become **sticky**, leading to sequestration in capillaries of vital organs, including the kidneys, resulting in acute tubular necrosis [1]. *Vivax* - **Plasmodium vivax** typically causes milder forms of malaria, though it can occasionally lead to severe manifestations, **renal complications are rare** compared to P. falciparum [1]. - While it can cause some organ dysfunction, it generally does not cause the severe multi-organ involvement, particularly **acute renal failure**, that P. falciparum is known for [1]. *Malariae* - **Plasmodium malariae** is associated with a chronic form of malaria and is known to cause **nephrotic syndrome** (specifically malarial nephropathy) due to immune complex deposition, rather than acute renal failure [1]. - The renal pathology in P. malariae infection is typically a **glomerulonephritis** that develops after repeated infections, which is distinct from the acute renal failure seen with P. falciparum [1]. *Ovale* - **Plasmodium ovale** is the least common type of malaria and causes a benign form of the disease, similar to P. vivax [1]. - It rarely, if ever, causes severe complications like **renal failure** [1].

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: Serological testing of patient shows HBsAg, IgM anti-HBc and HBeAg positive. The patient has -

Acute hepatitis B with high infectivity. ***Acute hepatitis B with high infectivity*** - The presence of **HBsAg** (hepatitis B surface antigen) indicates active infection, while **IgM anti-HBc** (IgM antibody to hepatitis B core antigen) is a marker of recent or acute infection [1]. - **HBeAg** (hepatitis B e-antigen) positivity signifies active viral replication and a high likelihood of infectivity [1]. *Chronic hepatitis B with low infectivity (not acute)* - **Chronic hepatitis B** is characterized by the presence of **HBsAg for more than six months**, but **IgM anti-HBc** would typically be negative; instead, **IgG anti-HBc** would be positive [1]. - **Low infectivity** would be indicated by the absence of **HBeAg**, replaced by **anti-HBe** (antibody to HBeAg) [1]. *Chronic hepatitis with high infectivity* - This diagnosis would show positive **HBsAg and HBeAg**, but the absence of **IgM anti-HBc** (presence of **IgG anti-HBc** instead) would distinguish it from acute infection [1]. - The presence of **IgM anti-HBc** is a crucial marker for an acute phase of hepatitis B rather than chronic. *Acute on chronic hepatitis* - This scenario would involve a patient with pre-existing **chronic hepatitis B** (positive HBsAg, IgG anti-HBc) experiencing a new acute flare-up, which could involve a resurgence of **HBeAg** or a new acute viral insult. - While **HBsAg** and **HBeAg** would be positive, the key differentiator would be the presence of both **IgM anti-HBc** (indicating the acute component) and **IgG anti-HBc** (indicating the chronic component), which is not fully described here to confirm acute on chronic.

Q: What is the most significant risk factor for transitional cell carcinoma of the bladder?

Schistosomiasis. ***Schistosomiasis*** - Schistosomiasis, especially caused by *Schistosoma haematobium*, is strongly associated with the development of **transitional cell carcinoma** of the bladder. - The inflammation and chronic irritation of the bladder epithelium by the parasite lead to increased risk of **malignant transformation**. *None* - This option implies that there are **no known causes**, which is incorrect, as there are well-established associations, particularly with schistosomiasis. - Transitional cell carcinoma of the bladder has **known risk factors** and associations, contrary to this option's suggestion. *Ascariasis* - Ascariasis is primarily an **intestinal infection** caused by *Ascaris lumbricoides* and is not linked to bladder cancer. - It is more associated with **pulmonary symptoms** or intestinal obstruction rather than urothelial malignancies. *Malaria* - Malaria is caused by *Plasmodium* species and typically results in **fever** and **splenomegaly**, not bladder cancer. - There is no significant association between malaria infections and the development of **transitional cell carcinoma**.

Q: All of the following provide protection against malaria except which of the following?

PNH. ***PNH*** - Paroxysmal Nocturnal Hemoglobinuria (PNH) does not provide any **protection against malaria**; it is an acquired bone marrow disorder. - While it leads to increased hemolysis and thrombosis, it does not affect **malaria susceptibility** directly. *Duffy blood group* - The Duffy blood group has specific antigens that are a **receptor for Plasmodium vivax**, making individuals with a Duffy-negative phenotype resistant to this type of malaria. - Therefore, Duffy blood group status can indeed serve as a protective factor against certain malaria strains. *Hereditary spherocytosis* - This condition results in **spherical red blood cells** [1], causing hemolytic anemia, but it does not confer protection against malaria. - People with hereditary spherocytosis do not have a lower prevalence of malaria and may still be susceptible to infection. *Sickle cell anemia* - Individuals with sickle cell anemia often exhibit **increased resistance to malaria**, especially against Plasmodium falciparum [2]. - The sickling of red blood cells under low oxygen conditions creates an unfavorable environment for the malarial parasites to thrive [2, 3].

Q: Procalcitonin is considered a marker for:

Sepsis. **Sepsis** - **Procalcitonin** (PCT) levels significantly rise in response to bacterial infections and **sepsis**, making it a useful diagnostic and prognostic marker. - Its levels correlate with the severity of bacterial infection and can help differentiate bacterial from viral etiologies. *Medullary thyroid carcinoma* - **Medullary thyroid carcinoma** (MTC) is characterized by the production of **calcitonin**, a different hormone from procalcitonin, by the parafollicular C cells of the thyroid. - While calcitonin is a tumor marker for MTC, **procalcitonin** is not. *Vitamin D resistant rickets* - **Vitamin D resistant rickets** (also known as X-linked hypophosphatemia) is a genetic disorder characterized by impaired phosphate reabsorption in the kidneys [1]. - It is associated with low phosphate levels and bone deformities, but not with elevated procalcitonin [1]. *Parathyroid adenoma* - A **parathyroid adenoma** leads to primary hyperparathyroidism, characterized by excessive production of **parathyroid hormone (PTH)** [1]. - This results in hypercalcemia and hypophosphatemia, with no direct link to procalcitonin levels [1].

Question 1

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 2

Meningitis with rash is seen in -

Accepted Answer

Neisseria meningitidis

Answer

H. influenzae

Answer

Strepto. agalactae

Answer

Pneumococcus

Question 3

HIV post exposure prophylaxis should be started within?

Accepted Answer

72 hrs

Answer

1-2 hrs

Answer

14 hrs

Answer

18 hrs

Question 4

Tabes dorsalis is seen in -

Accepted Answer

Tertiary syphilis

Answer

Primary syphilis

Answer

Latent syphilis

Answer

Secondary syphilis

Question 5

Which type of malaria is most commonly associated with renal failure?

Accepted Answer

Falciparum

Answer

Vivax

Answer

Malariae

Answer

Ovale

Question 6

Which species of malaria is associated with nephrotic syndrome?

Accepted Answer

P. malariae

Answer

P. vivax

Answer

P. falciparum

Answer

P. ovale

Question 7

Serological testing of patient shows HBsAg, IgM anti-HBc and HBeAg positive. The patient has -

Accepted Answer

Acute hepatitis B with high infectivity

Answer

Chronic hepatitis with high infectivity

Answer

Acute on chronic hepatitis

Answer

Chronic hepatitis B with low infectivity (not acute)

Question 8

What is the most significant risk factor for transitional cell carcinoma of the bladder?

Accepted Answer

Schistosomiasis

Answer

Ascariasis

Answer

Malaria

Answer

None of the options

Question 9

All of the following provide protection against malaria except which of the following?

Accepted Answer

PNH

Answer

Sickle cell anemia

Answer

Hereditary spherocytosis

Answer

Duffy blood group

Question 10

Procalcitonin is considered a marker for:

Accepted Answer

Sepsis

Answer

Medullary thyroid carcinoma

Answer

Parathyroid adenoma

Answer

Vitamin D resistant rickets

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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