Infectious Diseases Practice Questions

Q: A patient with large, penetrating vegetations on his mitral and aortic valves develops severe headaches. Funduscopic examination reveals papilledema. CT scan of the brain demonstrates a ring-enhancing lesion. Which of the following organisms is the most likely cause of the patient's disorder?

Staphylococcus aureus. ***Staphylococcus aureus*** - This organism is a common cause of **infective endocarditis**, particularly in patients with intravenous drug use, and is known for producing **large, destructive vegetations** that can readily embolize [2]. - The development of **severe headaches**, **papilledema**, and a **ring-enhancing brain lesion** strongly suggests a **septic embolism** leading to a **brain abscess**, a known complication of infective endocarditis caused by virulent organisms like *S. aureus* [1], [2]. *Herpesvirus* - Herpesvirus infections, such as **HSV-1**, can cause **encephalitis**, which might present with headaches and neurological signs, but they are not typically associated with **infective endocarditis** or the formation of **septic emboli** from heart valves. - While herpes encephalitis can cause ring-enhancing lesions in specific brain regions (e.g., temporal or frontal lobes), the primary presentation here points to a systemic embolic source from the heart. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* can cause endocarditis, though it is less common than *Staphylococcus aureus* and often occurs in patients with pre-existing valvular disease. - While septic emboli can occur, *S. pneumoniae* endocarditis is not as frequently associated with **large, destructive vegetations** and subsequent brain abscess formation as *S. aureus* [2]. *Mycobacterium tuberculosis* - **Tuberculous meningitis** can cause severe headaches, papilledema, and ring-enhancing lesions (tuberculomas) in the brain. - However, **tuberculous_endocarditis** is extremely rare and typically does not manifest with large, destructive vegetations or, more importantly, with a primary infectious source from the heart valves as indicated by the "large, penetrating vegetations."

Q: Which of the following is the leading cause of death in brucellosis?

Endocarditis. ***Endocarditis*** - **Endocarditis** is the most common cause of death in brucellosis, particularly when involving the **aortic valve** [1]. - It often requires a combination of prolonged **antibiotic therapy** and **surgical intervention**. *Pneumonia* - While pulmonary involvement can occur in brucellosis, including **bronchitis** and **pneumonia**, it is rarely the leading cause of death. - Respiratory symptoms are generally mild and respond well to treatment. *Suppurative abscesses* - **Focal abscesses** can form in various organs in brucellosis, such as the liver or spleen [1]. - However, while serious, they are not as frequent a cause of mortality as endocarditis. *Mycotic aneurysms* - Though rare, **vascular complications** like mycotic aneurysms can occur in brucellosis, potentially leading to rupture and death. - However, their incidence is much lower compared to the mortality associated with brucella endocarditis.

Q: Which of the following is not a complication of infective endocarditis?

Myocardial infarction. ***Myocardial infarction*** - While infective endocarditis can lead to various cardiac complications, **myocardial infarction** due to direct coronary artery occlusion by emboli from vegetations is **rare** and not considered a typical complication. [1] - Myocardial infarction is more commonly associated with **atherosclerotic coronary artery disease**. *Myocardial ring abscess* - This is a common and severe local complication of infective endocarditis, often occurring in cases involving **virulent organisms** or **prosthetic valves**. [1] - An abscess can extend into the **myocardium**, conduction system, or pericardium, leading to heart block or valvular dehiscence. *Focal and diffuse glomerulonephritis* - These are **immune-mediated renal complications** of infective endocarditis, caused by the deposition of immune complexes in the glomeruli. [1] - Often presents with **hematuria**, proteinuria, and renal impairment, reflecting the systemic inflammatory response. [1] *Suppurative pericarditis* - This can occur if the infection from the endocarditic vegetation extends into the **pericardial space**, either directly or via a myocardial abscess. - It involves **purulent inflammation** of the pericardium, leading to chest pain, fever, and potentially tamponade.

Q: The following parasitic infections predispose to malignancies: A) Paragonimus westermani B) Guinea worm infection C) Clonorchiasis D) Schistosomiasis

C and D. ***C and D*** - **Clonorchiasis**, caused by *Clonorchis sinensis*, is strongly linked to **cholangiocarcinoma**, cancer of the bile ducts. - **Schistosomiasis**, particularly infection with *Schistosoma haematobium*, is a significant risk factor for **bladder cancer** [1]. *A and B* - **Paragonimus westermani** (lung fluke) can cause chronic inflammation and fibrosis in the lungs but is not directly associated with malignancy. - **Guinea worm infection** (*Dracunculus medinensis*) causes painful ulcers but does not predispose to cancer. *B and D* - **Guinea worm infection** does not cause cancer. - While **Schistosomiasis** does predispose to malignancy [1], the pairing with Guinea worm makes this option incorrect overall. *A and C* - **Paragonimus westermani** is not known to cause malignancy. - **Clonorchiasis** is linked to malignancy, but its pairing with an incorrect option makes this choice wrong.

Q: WHO AIDS defining illnesses are all EXCEPT:

Persistent generalized lymphadenopathy. ***Persistent generalized lymphadenopathy*** - While associated with HIV infection, **persistent generalized lymphadenopathy** itself is not classified as an **AIDS-defining illness** by the WHO or CDC, but rather a common manifestation of chronic HIV infection (Stage 1 or 2) [1]. - AIDS-defining illnesses are typically severe opportunistic infections or cancers that occur when the immune system is severely compromised (CD4 count below 200 cells/µL). *P. carinii pneumonia* - **P. carinii pneumonia** (now known as **Pneumocystis jirovecii pneumonia** or **PJP**) is a classic and common **AIDS-defining opportunistic infection**. - Its presence indicates severe immunosuppression, often with CD4 counts below 200 cells/µL. *CMV retinitis* - **Cytomegalovirus (CMV) retinitis** is a severe opportunistic infection, particularly of the eye, that is recognized as an **AIDS-defining illness**. - It signifies profound immunodeficiency, typically with CD4 counts below 50 cells/µL. *Oropharyngeal candidiasis* - While common in HIV-infected individuals, **oropharyngeal candidiasis** (thrush) alone is generally not considered an **AIDS-defining illness** [1]. - It is classified as an HIV Stage 2 condition, indicating moderate immune compromise rather than severe, AIDS-defining immunosuppression [1].

Q: Tom-smith arthritis results from

Staphylococcus aureus infection. ***Staphylococcus aureus infection*** - **Tom-smith arthritis** (more commonly known as **septic arthritis** or infectious arthritis) is most frequently caused by **Staphylococcus aureus**, especially in adults and older children [1]. - The bacteria can enter the joint directly via trauma, surgery, or spread hematogenously from a distant infection, leading to rapid joint destruction if untreated [1]. *Streptococcus pyogenes infection* - While **Streptococcus pyogenes** can cause infectious arthritis, it is a less common cause than **Staphylococcus aureus** [1]. - It is more classically associated with **rheumatic fever** following pharyngitis, which involves migratory polyarthritis but is an immunologically mediated process, not direct bacterial infection of the joint in the same way. *Haemophilus influenzae infection* - **Haemophilus influenzae type b (Hib)** was once a common cause of septic arthritis in unvaccinated children but is now rare due to widespread vaccination. - In adults, other bacterial causes are more prevalent for septic arthritis. *Escherichia coli infection* - **Escherichia coli** can cause septic arthritis, particularly in neonates, immunocompromised individuals, or following genitourinary tract infections or intra-abdominal sepsis. - However, it is less common than **Staphylococcus aureus** as the primary cause of acute septic arthritis in otherwise healthy adults.

Q: In the management of leprosy, Lepromin test is most useful for:-

Prognosis. Prognosis - A positive Lepromin test indicates a strong cell-mediated immune response to Mycobacterium leprae, which is associated with the tuberculoid form of leprosy and a better prognosis [1]. - A negative test suggests a poor immune response, seen in lepromatous leprosy [1], which is associated with a more severe, disseminated disease and worse prognosis. Epidemiological investigations - While it reflects immune status, the Lepromin test is not primarily used for identifying active cases or tracking disease transmission in the general population. - Its utility in population-level studies is limited as it doesn't distinguish between past exposure, subclinical infection, or present disease. Treatment - The Lepromin test does not guide the choice of specific medications or the duration of multi-drug therapy (MDT) for leprosy. - Treatment regimens are determined by the classification of leprosy (paucibacillary or multibacillary) based on clinical and bacteriological findings. Herd immunity - Herd immunity applies to vaccine-preventable diseases where a high percentage of the population is immune, indirectly protecting susceptible individuals. - Leprosy is not typically controlled through herd immunity, and the Lepromin test does not assess population-level protection.

Q: The probable interval between throat infection and onset of rheumatic fever is:

2-4 weeks. ***2-4 weeks*** - The latency period between a **streptococcal pharyngeal infection** (strep throat) and the onset of acute rheumatic fever is typically 2 to 4 weeks [1]. - This interval is necessary for the immune response to the *Streptococcus pyogenes* infection to develop and cross-react with host tissues, leading to the autoimmune manifestations of rheumatic fever [1]. *2-4 months* - An interval of 2-4 months is generally too long for the typical presentation of **acute rheumatic fever** following a strep throat [1]. - Such a prolonged period would make the direct immunological link less probable for the initial acute event. *2-4 hours* - An interval of 2-4 hours is far too short for the development of **acute rheumatic fever**, which is an autoimmune complication. - Autoimmune responses require time for antigen presentation, lymphocyte activation, and antibody production. *2-4 days* - An interval of 2-4 days is generally too short for the immune system to mount a sufficient **autoimmune response** leading to the clinical manifestations of acute rheumatic fever. - While other post-streptococcal conditions like **scarlet fever** may manifest within this timeframe, rheumatic fever takes longer.

Q: NOT a good prognostic factor for TB spine

Rapid onset. ***Rapid onset*** - A **rapid onset** of symptoms in TB spine can indicate aggressive disease progression and may be associated with a poorer prognosis [1]. - This suggests the infection is advancing quickly, potentially leading to more severe neurological deficits or bone destruction before effective treatment can be initiated [1]. *Young age* - **Young age** is generally considered a good prognostic factor for TB spine, as younger patients often have better bone healing capacity and immune responses. - They tend to respond more effectively to antitubercular treatment and have a lower incidence of severe complications compared to older adults. *Good immunity* - A **robust immune system** is crucial for controlling *Mycobacterium tuberculosis* infection and is a key factor in achieving a favorable outcome in TB spine. - Patients with good immunity are more likely to clear the infection, prevent widespread dissemination, and experience less severe bone and neurological damage. *Early diagnosis* - **Early diagnosis** allows for prompt initiation of appropriate antitubercular therapy, which is essential for preventing disease progression and minimizing complications. - **Timely treatment** reduces the risk of spinal deformities, neurological deficits, and the need for extensive surgical intervention, leading to a better prognosis.

Question 1

A patient with large, penetrating vegetations on his mitral and aortic valves develops severe headaches. Funduscopic examination reveals papilledema. CT scan of the brain demonstrates a ring-enhancing lesion. Which of the following organisms is the most likely cause of the patient's disorder?

Accepted Answer

Staphylococcus aureus

Answer

Herpesvirus

Answer

Streptococcus pneumoniae

Answer

Mycobacterium tuberculosis

Question 2

Which of the following is the leading cause of death in brucellosis?

Accepted Answer

Endocarditis

Answer

Pneumonia

Answer

Suppurative abscesses

Answer

Mycotic aneurysms

Question 3

Which of the following is not a complication of infective endocarditis?

Accepted Answer

Myocardial infarction

Answer

Focal and diffuse glomerulonephritis

Answer

Myocardial ring abscess

Answer

Suppurative pericarditis

Question 4

The typical CSF profile in cases of viral meningitis after 48 hours of onset is -

Accepted Answer

Lymphocytic pleocytosis, normal glucose level, normal or slightly elevated protein level

Answer

Neutrophilic pleocytosis, raised glucose level, normal protein level

Answer

Lymphocytic pleocytosis, low glucose level, low protein level

Answer

Neutrophilic pleocytosis, normal glucose level, elevated protein level

Question 5

The following parasitic infections predispose to malignancies: A) Paragonimus westermani B) Guinea worm infection C) Clonorchiasis D) Schistosomiasis

Accepted Answer

C and D

Answer

A and B

Answer

B and D

Answer

A and C

Question 6

WHO AIDS defining illnesses are all EXCEPT:

Accepted Answer

Persistent generalized lymphadenopathy

Answer

P. carinii pneumonia

Answer

CMV retinitis

Answer

Oropharyngeal candidiasis

Question 7

Tom-smith arthritis results from

Accepted Answer

Staphylococcus aureus infection

Answer

Streptococcus pyogenes infection

Answer

Haemophilus influenzae infection

Answer

Escherichia coli infection

Question 8

In the management of leprosy, Lepromin test is most useful for:-

Accepted Answer

Prognosis

Answer

Epidemiological investigations

Answer

Treatment

Answer

Herd immunity

Question 9

The probable interval between throat infection and onset of rheumatic fever is:

Accepted Answer

2-4 weeks

Answer

2-4 months

Answer

2-4 hours

Answer

2-4 days

Question 10

NOT a good prognostic factor for TB spine

Accepted Answer

Rapid onset

Answer

Young age

Answer

Good immunity

Answer

Early diagnosis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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