Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1361: Roth spots are specifically associated with which condition?

A. Papilledema
B. Diabetes
C. Infective endocarditis (Correct Answer)
D. Hypertension

Explanation: ***Infective endocarditis*** - **Roth spots** are retinal hemorrhages with a pale center, typically caused by **immune complex deposition** or **embolism** from infective endocarditis. - Their presence is a classic **ophthalmologic sign** associated with this serious infection of the heart valves. *Papilledema* - This condition involves **optic disc swelling** due to increased intracranial pressure, not retinal hemorrhages with pale centers. - It would typically manifest with visual disturbances like transient vision loss, not specific vascular lesions. *Diabetes* - **Diabetic retinopathy** involves microaneurysms, hemorrhages, and exudates, but Roth spots are not a characteristic feature. - Retinal changes in diabetes are primarily due to **microvascular damage** from chronic hyperglycemia. *Hypertension* - **Hypertensive retinopathy** can cause retinal hemorrhages, cotton wool spots, and arteriolar narrowing. - However, the specific appearance of Roth spots with a pale center is not characteristic of hypertensive retinopathy.

Question 1362: A man presents with fever, weight loss, and cough; the Mantoux test reads an induration of 17 x 19 mm, and sputum cytology is negative for acid-fast bacilli. What is the most likely diagnosis?

A. Pulmonary tuberculosis (Correct Answer)
B. Histoplasmosis
C. Influenza
D. Bacterial pneumonia

Explanation: ***Pulmonary tuberculosis*** - The combination of **fever**, **weight loss**, and **cough** are classic symptoms of tuberculosis [1]. - A **Mantoux induration of 17x19 mm** indicates a significant cell-mediated immune response to *Mycobacterium tuberculosis*, supporting the diagnosis even with initial negative sputum cytology [2]. *Histoplasmosis* - While it can cause fever, weight loss, and cough, a **positive Mantoux test** is not characteristic of histoplasmosis. - Diagnosis typically involves fungal cultures, serology, or antigen detection, not tuberculin skin testing. *Influenza* - Influenza is an **acute viral infection** presenting with sudden onset of fever, cough, and myalgia, but **chronic weight loss** is not a typical feature. - The **Mantoux test** being positive does not point towards influenza. *Bacterial pneumonia* - This typically presents with an **acute onset** of fever, productive cough, and dyspnea, while **weight loss** and a **positive Mantoux test** are not typical findings. - It rapidly responds to antibiotics, unlike the more chronic presentation suggested here.

Question 1363: All the following statements about primary tuberculosis are true except

A. Fibrocasseous lesion
B. Phlyctenular conjunctivitis
C. Cavitary lesion (Correct Answer)
D. Pleural effusion

Explanation: ***Cavitary lesion*** - **Cavitary lesions** are typically associated with **post-primary (reactivation) tuberculosis**, which occurs when dormant primary infection reactivates, usually in immunocompromised individuals [3]. - In primary tuberculosis, initial infection often leads to **Ghon complexes** or calcified granulomas, but not typically cavitary disease at the primary stage [1]. *Pleural effusion* - **Pleural effusions** can occur in **primary tuberculosis** as a hypersensitivity reaction to mycobacterial antigens or due to direct extension of infection into the pleural space [2]. - They are often seen in younger patients and usually resolve with anti-TB treatment. *Fibrocaseous lesion* - **Fibrocaseous lesions** represent the typical pathology of primary tuberculosis, where granuloma formation with central **caseous necrosis** and fibrous encapsulation occurs [1]. - This lesion may eventually heal with calcification (forming a Ghon focus) or progress [1]. *Phlyctenular conjunctivitis* - **Phlyctenular conjunctivitis** is an immune-mediated hypersensitivity reaction to tuberculoproteins, often occurring during or after primary tuberculosis. - It presents as small, raised nodules on the conjunctiva or cornea and is a recognized ophthalmic manifestation of TB exposure.

Question 1364: Which of the following statements is true about infective endocarditis in IV drug abusers?

A. Candida is a common cause.
B. Pulmonary valve is commonly involved
C. Tricuspid valve is most commonly involved (Correct Answer)
D. Staphylococcus aureus is rarely the commonest organism.

Explanation: ***Tricuspid valve is most commonly involved*** - In **IV drug abusers**, the **tricuspid valve** is most often affected due to direct inoculation of pathogens through contaminated needles. - This results in **right-sided endocarditis**, commonly associated with **Staphylococcus aureus** infections [2], [3]. *Staphylococcus aureus is the most common organism.* - While **Staphylococcus aureus** is prevalent [3], [4], it is **not the only organism**; other bacteria can also cause infective endocarditis in this population. - The statement is somewhat misleading as it does not emphasize the broader range of organisms involved. *Pulmonary valve is commonly involved* - The **pulmonary valve** is typically not affected in infective endocarditis related to IV drug use; the focus is primarily on the **tricuspid valve**. - Right-sided endocarditis predominantly affects the **tricuspid valve** due to the route of infection, making this statement incorrect. *Candida is a common cause of infective endocarditis.* - **Candida** is a rare cause of infective endocarditis compared to bacterial causes, especially in IV drug users [1]. - This fungal organism is more associated with **compromised immunity** and not common in standard settings of IV drug abuse, though it can occur via contamination of lemon juice [1].

Question 1365: A patient with acute leukemia is admitted with febrile neutropenia. On day four of being treated with broad-spectrum antibiotics, his fever increases. Chest X-ray shows bilateral fluffy infiltrates. Which of the following should be the most appropriate next step in the management?

A. Add antifungal therapy (Correct Answer)
B. Add antiviral therapy
C. Add cotrimoxazole
D. Continue chemotherapy

Explanation: Correct: Add antifungal therapy - Increasing fever despite broad-spectrum antibiotics in a neutropenic patient with bilateral fluffy infiltrates on chest X-ray strongly indicates an underlying fungal infection [1], [3]. - Empirical antifungal therapy is a crucial next step in this high-risk population to prevent severe morbidity and mortality associated with invasive fungal infections [1]. Add antiviral therapy - While viral infections can occur in immunocompromised patients, the presentation of persistent fever despite antibiotics and fluffy infiltrates is less characteristic of a primary viral pneumonia requiring targeted antiviral therapy at this initial stage [2]. - The patient's clinical picture is more suggestive of a fungal etiology after failing antibacterial treatment. Add cotrimoxazole - Cotrimoxazole (trimethoprim/sulfamethoxazole) is primarily used for Pneumocystis jirovecii pneumonia (PCP) prophylaxis or treatment, or for certain bacterial infections. - The clinical scenario, particularly the bilateral fluffy infiltrates in a neutropenic patient failing broad-spectrum antibiotics, is less typical for a PCP presentation and doesn't point to a need for this specific antibiotic. Continue chemotherapy - The patient is currently experiencing febrile neutropenia [2], a life-threatening complication of chemotherapy. - Continuing chemotherapy would further exacerbate the neutropenia and potentially worsen the infection, without addressing the underlying cause of the persistent fever and infiltrates.

Question 1366: Which of the following statements about the Mantoux test is NOT true?

A. Result is seen after 3 weeks (Correct Answer)
B. > 9mm induration is taken as positive
C. Type IV Hypersensitivity
D. PPD RT-23 with tween 80 used as strain

Explanation: Result is seen after 3 weeks - The results of a Mantoux test, indicating the induration size, are read **48 to 72 hours** after the injection, not three weeks. - Waiting three weeks would lead to a missed or inaccurate reading, as the immune response would have waned. *PPD RT-23 with tween 80 used as strain* - The Mantoux test uses a **Purified Protein Derivative (PPD)**, often designated as **PPD RT-23**, derived from Mycobacterium tuberculosis. - **Tween 80** is commonly added to PPD preparations to stabilize the protein and prevent it from adhering to the container, ensuring accurate dosing. * > 9mm induration is taken as positive* - An induration of **greater than 9mm** (often 10mm or more, depending on risk factors) is generally considered a **positive result** in the Mantoux test. - The interpretation of induration size varies based on the individual's risk factors for tuberculosis and exposure history. *Type IV Hypersensitivity* - The Mantoux test elicits a **Type IV hypersensitivity reaction**, also known as a **delayed-type hypersensitivity (DTH)** reaction. - This reaction involves T-cells and macrophages, which migrate to the injection site, causing induration and erythema within 48 to 72 hours.

Question 1367: A pregnant woman from Bihar presents with hepatic encephalopathy. What is the likely diagnosis?

A. Acute fatty liver of pregnancy
B. Sepsis
C. Hepatitis E (Correct Answer)
D. Hepatitis B

Explanation: ***Hepatitis E*** - **Hepatitis E** is highly prevalent in **Bihar**, and its infection in pregnant women is associated with a severe course, including a high risk of **fulminant hepatic failure** and **hepatic encephalopathy**. - **Mortality rates** are significantly higher in pregnant women due to this virus, making it the most likely cause of their presentation. *Sepsis* - While sepsis can lead to **hepatic dysfunction**, it typically presents with other signs of systemic infection like **fever**, **tachycardia**, and **hypotension**, which are not mentioned as primary symptoms. - Sepsis-induced liver injury usually manifests as **cholestasis** or **ischemic hepatitis**, rather than primarily **hepatic encephalopathy** unless there's pre-existing liver disease. *Acute fatty liver of pregnancy* - This condition can cause **hepatic encephalopathy** but is often associated with symptoms like **nausea**, **vomiting**, **abdominal pain**, and **hypoglycemia** [2]. - While serious, its prevalence may be lower than infectious causes like Hepatitis E in endemic regions, and the geographical context strongly points towards Hepatitis E [2]. *Hepatitis B* - Although **Hepatitis B** can cause chronic liver disease and acute exacerbations leading to **hepatic encephalopathy**, it typically presents differently in acute infection or during chronic carriership [1]. - Acute Hepatitis B in pregnancy is less commonly associated with **fulminant hepatic failure** compared to Hepatitis E in endemic settings.

Question 1368: Which marker is typically not present during the acute phase of hepatitis B infection?

A. IgM Anti HBe Ag (Correct Answer)
B. HBV DNA
C. HBs Ag
D. IgM Anti HBc Ag

Explanation: ***IgM Anti HBe Ag*** - **IgM anti-HBe** is not a typical marker during acute hepatitis B because **HBeAg** itself is secreted early in infection, and antibodies against it (anti-HBe) usually develop during seroconversion from acute to chronic infection, or during resolution [1]. - The presence of **anti-HBe** signifies reduced infectivity and often indicates the beginning of viral clearance or a transition to a lower replication state, rather than the initial acute phase [1]. *HBV DNA* - **HBV DNA** is typically present during the acute phase of hepatitis B as it indicates active viral replication and is detectable in the blood soon after infection [1]. - High levels of HBV DNA correlate with high infectivity and active disease a hallmark of acute infection. *HBs Ag* - **HBsAg (Hepatitis B surface antigen)** is the *first detectable marker* of acute hepatitis B infection, appearing even before symptoms begin [1]. - Its presence indicates active infection, whether acute or chronic, and it remains detectable throughout the acute phase [1]. *IgM Anti HBc Ag* - **IgM anti-HBc (IgM antibody to hepatitis B core antigen)** is a reliable marker for *acute or recent hepatitis B infection* [1]. - It becomes detectable shortly after HBsAg and can persist for several months, indicating an ongoing or recent acute process [1].

Question 1369: Death in poliomyelitis is due to:

A. Severe neurogenic shock
B. Respiratory muscle failure (Correct Answer)
C. Secondary infection complications
D. Cardiac complications

Explanation: Respiratory muscle failure [1] - The poliovirus primarily targets and destroys motor neurons within the anterior horn cells of the spinal cord and brainstem. - When the motor neurons controlling the diaphragm and intercostal muscles are affected, it leads to paralysis and inability to breathe, resulting in death. *Severe neurogenic shock* - While poliomyelitis can affect the nervous system, neurogenic shock (characterized by hypotension and bradycardia due to loss of sympathetic tone) is not the primary mechanism of death. - The direct paralysis of respiratory muscles is a more immediate and common cause of fatality. *Secondary infection complications* - Secondary infections, such as pneumonia, can occur in severely ill polio patients due to prolonged immobility and compromised pulmonary function. - However, these are typically complications arising from the primary respiratory muscle paralysis, rather than the initial and direct cause of death. *Cardiac complications* - Although rare, some cases of poliomyelitis can involve myocarditis or other cardiac issues. - These are not the most common or direct cause of death; respiratory failure remains the overwhelming primary cause. [1]

Question 1370: After splenectomy, which is the most important vaccine that needs to be given?

A. Rotavirus
B. BCG
C. MMR
D. Pneumococcal (Correct Answer)

Explanation: ***Pneumococcal*** - The spleen plays a crucial role in clearing **encapsulated bacteria**, such as *Streptococcus pneumoniae* [1], [2]. - Patients who have undergone a **splenectomy** are at significantly increased risk of severe, life-threatening **pneumococcal infections**, making this vaccine essential [3]. *Rotavirus* - This vaccine protects against **rotavirus infections**, which primarily cause **severe gastroenteritis** in infants and young children. - There is no direct link between **splenectomy** and an increased susceptibility to severe rotavirus disease that would prioritize this vaccine over others. *BCG* - The **BCG (Bacillus Calmette-Guérin) vaccine** is used to prevent **tuberculosis**. - While immunocompromised individuals may be at higher risk for tuberculosis, **splenectomy** itself does not specifically increase susceptibility to *Mycobacterium tuberculosis* in a way that makes BCG the most critical post-splenectomy vaccine. *MMR* - The **MMR (Measles, Mumps, and Rubella) vaccine** protects against common viral diseases. - These are **viral infections**, and the absence of the spleen does not specifically predispose individuals to more severe outcomes from these diseases to the extent seen with encapsulated bacterial infections.

Practice by Chapter

Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

Practice Questions

HIV/AIDS and Related Infections

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Tuberculosis and Mycobacterial Diseases

Practice Questions

Tropical and Parasitic Infections

Practice Questions

Viral Infections (Hepatitis, Herpes, etc.)

Practice Questions

Healthcare-Associated Infections

Practice Questions

Fungal Infections

Practice Questions

Sepsis and Septic Shock

Practice Questions

Infection in Immunocompromised Hosts

Practice Questions

Emerging and Re-emerging Infections

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Antimicrobial Resistance

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Vaccination Principles

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