Infectious Diseases Practice Questions

Q: In chronic Hepatitis B (HBV) infection, the presence of HBeAg suggests which of the following?

Ongoing viral replication. **Explanation:** The **Hepatitis B e-antigen (HBeAg)** is a soluble protein derived from the precore region of the HBV genome [1]. It serves as a qualitative marker of **active viral replication** and high infectivity [1]. 1. **Why Option A is Correct:** HBeAg is secreted by hepatocytes only when the virus is actively replicating. Its presence in the serum correlates with high levels of HBV DNA and indicates that the patient is highly contagious [1]. The transition from HBeAg-positive to anti-HBe (seroconversion) usually signals a reduction in viral load and a transition to a lower replicative state [1]. 2. **Why Other Options are Incorrect:** * **Option B (Resolving infection):** Resolution is characterized by the disappearance of HBsAg and the appearance of **Anti-HBs** [1]. HBeAg persistence indicates chronicity, not resolution. * **Option C & D (Cirrhosis/Hepatoma):** While chronic HBV is a major risk factor for cirrhosis and Hepatocellular Carcinoma (HCC), HBeAg is a marker of replication, not a direct marker of structural liver damage or malignancy [1]. Notably, HCC can occur in "HBeAg-negative" patients if they have high viral DNA or have integrated the virus into their genome. **NEET-PG High-Yield Pearls:** * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. The only marker present is **Anti-HBc IgM** [1]. * **Precore Mutant:** A condition where the patient has high HBV DNA and active liver disease but is **HBeAg negative** (due to a mutation in the precore region that prevents HBeAg secretion) [1]. * **Best indicator of HBV infectivity:** HBV DNA levels (quantitative) or HBeAg (qualitative) [1]. * **First marker to appear:** HBsAg [1].

Q: What is the most common pulmonary manifestation in AIDS?

Pneumonia. **Explanation:** The correct answer is **Pneumonia**. In patients with HIV/AIDS, the lung is the most common site of opportunistic infections. Among all pulmonary complications, **Bacterial Pneumonia** (specifically caused by *Streptococcus pneumoniae*) is the most frequent manifestation overall [3]. While *Pneumocystis jirovecii* pneumonia (PCP) is a classic AIDS-defining illness [2], pyogenic bacterial pneumonia occurs at a higher frequency across all CD4 counts [1]. **Analysis of Options:** * **A. Tuberculosis (TB):** TB is the most common **opportunistic infection** and the leading cause of death in HIV patients in developing countries like India [1]. However, in terms of general pulmonary "manifestations" or occurrences, bacterial pneumonia remains more frequent. * **C. Bronchiectasis:** This is a chronic structural complication resulting from recurrent infections (like TB or bacterial pneumonia) but is not the most common primary manifestation [3]. * **D. Mycobacterium avium complex (MAC):** This typically presents as a late-stage disseminated disease when CD4 counts drop below 50 cells/µL [4]. It is less common than both TB and bacterial pneumonia. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of community-acquired pneumonia in HIV:** *Streptococcus pneumoniae* [3]. * **Most common opportunistic infection (OI) in India:** Tuberculosis [1]. * **Most common AIDS-defining illness (globally):** *Pneumocystis jirovecii* pneumonia (PCP) [2]. * **Radiology Tip:** Bacterial pneumonia usually presents with focal lobar consolidation, whereas PCP typically shows bilateral perihilar ground-glass opacities [1]. * **CD4 Thresholds:** TB can occur at any CD4 level; PCP usually occurs at <200 cells/µL; MAC occurs at <50 cells/µL [4].

Q: Which of the following laboratory markers characterizes the recumbent stage of Hepatitis B?

Anti HBc. ### Explanation The "recumbent stage" (also known as the **Window Period**) of Hepatitis B is a critical diagnostic phase where HBsAg has disappeared from the blood, but Anti-HBs antibodies have not yet reached detectable levels [1]. **1. Why Anti-HBc is Correct:** During the window period, the only reliable serological marker of a recent HBV infection is **Anti-HBc IgM** (Antibody to Hepatitis B core antigen) [1]. Since HBsAg is negative and Anti-HBs is not yet present, testing for Anti-HBc is the only way to diagnose an acute infection during this gap [1]. **2. Why the Other Options are Incorrect:** * **Anti-HBs Ag:** This antibody appears during the **recovery/convalescence phase** and signifies immunity (either via natural infection or vaccination) [1]. In the recumbent stage, it is still below detectable limits. * **Anti-HBe Ag:** This indicates a decrease in viral replication and infectivity. While it may appear early, it is not the definitive marker used to define the window period. * **Anti-HBV:** This is a non-specific term. Diagnostic protocols specifically look for antibodies against specific components (Surface, Core, or e-antigen) rather than a generic "Anti-HBV." **3. NEET-PG High-Yield Pearls:** * **Window Period Markers:** HBsAg (-), Anti-HBs (-), **Anti-HBc IgM (+)** [1]. * **HBsAg:** The first marker to appear in blood (as early as 1–2 weeks post-exposure) [1]. * **Anti-HBs:** The only marker present in a **vaccinated** individual (Anti-HBc will be negative in vaccinated persons) [1]. * **Chronic Infection:** Defined by the persistence of HBsAg for >6 months [1]. * **HBeAg:** Indicates high viral replication and maximum infectivity.

Q: What is the true statement regarding the treatment of hepatic amoebiasis?

Mostly treated conservatively. **Explanation:** Amoebic Liver Abscess (ALA), caused by *Entamoeba histolytica*, is the most common extra-intestinal manifestation of amoebiasis. **Why Option C is correct:** The mainstay of treatment for ALA is **medical management**. Over 90-95% of patients respond dramatically to nitroimidazoles (e.g., **Metronidazole** 750 mg TID for 7-10 days). Surgical intervention or aspiration is rarely required and is reserved for specific complications like imminent rupture, lack of clinical response within 48-72 hours, or very large left-lobe abscesses. **Why other options are incorrect:** * **Option A:** ALA is significantly **more common in males** (ratio approx. 10:1), likely due to the protective effect of menstrual blood loss (iron deficiency inhibits amoebic growth) and higher alcohol consumption in men. * **Option B:** In approximately 70-80% of cases, ALA presents as a **solitary lesion**, most commonly located in the **right lobe** (posterosuperior segment) due to the bulk of the liver and the streaming effect of portal blood flow. * **Option C:** Jaundice is **uncommon** in uncomplicated ALA. If present, it usually indicates a massive abscess compressing the biliary tree or secondary bacterial infection. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** Fever with right upper quadrant pain and "anchovy sauce" (chocolate brown) pus on aspiration. * **Diagnosis:** Ultrasound is the initial investigation; Serology (IHA/ELISA) is highly sensitive. * **Indications for Aspiration:** Large size (>10 cm), failure of medical therapy, left lobe abscess (risk of rupture into the pericardium), or to rule out a pyogenic abscess.

Q: A 55-year-old diabetic female patient presented with facial pain, numbness, conjunctival suffusion, and blurring of vision for 6 days. She was managed conservatively and discharged. After a week, she presented again with bilateral proptosis, chemosis, vision loss, and ophthalmoplegia, along with a characteristic lesion on the nose. A smear was prepared from the nasal lesion. What is the most appropriate initial management for a suspected fungal infection causing these symptoms?

Amphotericin B. ### Explanation **Diagnosis: Rhino-Orbito-Cerebral Mucormycosis (ROCM)** The clinical presentation of a diabetic patient with facial pain, proptosis, ophthalmoplegia, and a "characteristic lesion on the nose" (likely a black eschar) is classic for **Mucormycosis** [1]. This is an aggressive, angioinvasive fungal infection caused by fungi of the order Mucorales [1]. #### 1. Why Amphotericin B is Correct **Liposomal Amphotericin B** is the drug of choice and the first-line medical management for Mucormycosis [1]. It acts by binding to ergosterol in the fungal cell membrane, creating pores that lead to cell death. In ROCM, rapid initiation of high-dose Amphotericin B, along with aggressive surgical debridement and control of underlying risk factors (like diabetic ketoacidosis), is life-saving [1]. #### 2. Why Other Options are Incorrect * **B. Posaconazole:** While active against Mucorales, it is typically used as **salvage therapy** for patients intolerant to Amphotericin B or as step-down maintenance therapy. It is not the initial drug of choice for acute, fulminant disease. * **C. Itraconazole:** This azole has **no significant activity** against Mucorales. It is primarily used for Histoplasmosis, Blastomycosis, or Sporotrichosis. * **D. Caspofungin:** Echinocandins have **no activity** against Mucorales (which lack the target 1,3-β-D-glucan in their cell walls) [2]. They are used for Candida and Aspergillus infections [2]. #### 3. NEET-PG High-Yield Pearls * **Risk Factors:** Uncontrolled Diabetes Mellitus (especially DKA), neutropenia, and iron overload (deferoxamine use) [1]. * **Microscopy:** Look for **broad, ribbon-like, aseptate hyphae** with **right-angle (90°) branching**. * **Black Eschar:** Caused by tissue infarction due to the fungus invading blood vessels (angioinvasion) [1]. * **Radiology:** "Reverse Halo Sign" on chest CT is highly suggestive of pulmonary involvement.

Q: Fever, clubbing, and Osler's nodes are characteristic findings in which of the following conditions?

Infective endocarditis. **Explanation:** The correct answer is **Infective Endocarditis (IE)**. This condition involves an infection of the endocardial surface of the heart, typically the valves [1]. The clinical presentation is a triad of systemic infection, valvular destruction, and immunological/embolic phenomena [1]. * **Why it is correct:** **Fever** is the most common presenting symptom [2]. **Clubbing** is a classic sign of subacute IE (though less common in the antibiotic era) [1]. **Osler’s nodes** are painful, pea-sized, erythematous nodules found on the pads of fingers and toes; they are an **immunological phenomenon** caused by immune complex deposition in the skin [1]. **Analysis of Incorrect Options:** * **A. Typhoid Fever:** Characterized by "step-ladder" fever, bradycardia (Faget’s sign), and Rose spots. It does not cause clubbing or Osler’s nodes. * **B. Rheumatic Fever:** Presents with migratory polyarthritis, carditis, and subcutaneous nodules (painless, over bony prominences). While it involves the heart, Osler’s nodes are specific to IE [3]. * **C. Leptospirosis:** Typically presents with fever, conjunctival suffusion (redness without discharge), and calf tenderness. In severe cases (Weil’s disease), it involves jaundice and renal failure. **High-Yield Clinical Pearls for NEET-PG:** * **Duke’s Criteria:** Used for diagnosis. Major criteria include positive blood cultures and echocardiographic evidence of vegetation [4]. * **Peripheral Stigmata of IE:** * **Janeway Lesions:** Painless, hemorrhagic macules on palms/soles (Embolic). * **Roth Spots:** Retinal hemorrhages with pale centers (Immunological). * **Splinter Hemorrhages:** Linear streaks under the nails. * **Most common valve involved:** Mitral valve (except in IV drug users, where the **Tricuspid valve** is most common) [5]. * **Most common organism:** *Staphylococcus aureus* (Acute/IVDU) and *Viridans streptococci* (Subacute) [5].

Q: A 40-year-old man presents with fever, weight loss, and cough. His Mantoux test result is 18 x 19 mm, and sputum cytology is negative for Acid-Fast Bacilli (AFB). What is the most likely condition?

Pulmonary Tuberculosis. **Explanation:** The clinical presentation of fever, weight loss, and chronic cough in a 40-year-old male is a classic "constitutional" triad highly suggestive of **Pulmonary Tuberculosis (PTB)** [1]. 1. **Why the correct answer is right:** The **Mantoux test (TST)** result of 18 x 19 mm is strongly positive (induration >10 mm is significant in endemic areas like India) [2]. While a negative sputum smear for AFB does not rule out TB, it simply indicates a "paucibacillary" state or poor sample quality [3]. In clinical practice, if the clinical suspicion is high and the Mantoux is strongly positive, PTB remains the most likely diagnosis, often requiring further evaluation via Sputum CBNAAT (GeneXpert) or culture. 2. **Why other options are incorrect:** * **Pneumococcal Pneumonia:** Typically presents with acute onset high-grade fever, productive cough with rusty sputum, and leukocytosis, rather than chronic weight loss. * **Cryptococcal Infection:** Usually seen in immunocompromised patients (e.g., HIV/AIDS). While it can cause weight loss, it is far less common than TB in the general population. * **Viral Infection:** These are usually self-limiting, acute illnesses (lasting 1–2 weeks) and would not cause significant weight loss or a strongly positive Mantoux test. **Clinical Pearls for NEET-PG:** * **Mantoux Interpretation:** An induration of **≥15 mm** is considered positive in individuals with no known risk factors; **≥10 mm** is positive in high-prevalence areas or healthcare workers. * **Sputum Smear Sensitivity:** Conventional Ziehl-Neelsen (ZN) staining requires roughly 5,000–10,000 bacilli/ml to be positive [3]. A negative smear **never** excludes TB. * **Gold Standard:** Sputum culture (Liquid culture/MGIT) remains the gold standard for diagnosis, while **CBNAAT** is the preferred initial diagnostic test under NTEP guidelines.

Q: A 35-year-old male patient with a known case of HIV on Antiretroviral Therapy complains of fever, dyspnea, dry cough, and weight loss for the past 3 months. The chest X-ray of the patient is as below. What is your diagnosis?

Pneumocystis pneumonia. ***Pneumocystis pneumonia*** - **Bilateral perihilar ground-glass opacities** on chest X-ray along with **subacute presentation** of fever, dry cough, and dyspnea in an **HIV patient** is classic for **Pneumocystis jirovecii pneumonia (PCP)**. - Typically occurs when **CD4 count falls below 200 cells/μL** and presents with **gradual onset** over weeks to months with **weight loss** and **exertional dyspnea**. *Staphylococcal pneumonia* - Usually presents with **acute onset** and **productive cough** with **purulent sputum**, unlike the dry cough described. - Chest X-ray typically shows **lobar consolidation** or **cavitating lesions**, not bilateral ground-glass opacities. *Viral pneumonia* - Generally has a **more acute presentation** with **upper respiratory symptoms** like rhinorrhea and sore throat. - Chest X-ray shows **diffuse bilateral infiltrates** but lacks the characteristic **perihilar distribution** seen in PCP. *None of the above* - The clinical presentation and **bilateral perihilar ground-glass pattern** in an **immunocompromised HIV patient** is pathognomonic for PCP. - The **subacute timeline** of 3 months with **weight loss** further supports this diagnosis over other pneumonias.

Question 1

In chronic Hepatitis B (HBV) infection, the presence of HBeAg suggests which of the following?

Accepted Answer

Ongoing viral replication

Answer

Resolving infection

Answer

Development of cirrhosis

Answer

Development of Hepatoma

Question 2

What is the most common pulmonary manifestation in AIDS?

Accepted Answer

Pneumonia

Answer

Tuberculosis

Answer

Bronchiectasis

Answer

Mycobacterium avium complex

Question 3

Which of the following laboratory markers characterizes the recumbent stage of Hepatitis B?

Accepted Answer

Anti HBc

Answer

Anti HBs Ag

Answer

Anti HBe Ag

Answer

Anti HBV

Question 4

What is the true statement regarding the treatment of hepatic amoebiasis?

Accepted Answer

Mostly treated conservatively

Answer

More common in females

Answer

Multiple lesions

Answer

Jaundice is common

Question 5

A 55-year-old diabetic female patient presented with facial pain, numbness, conjunctival suffusion, and blurring of vision for 6 days. She was managed conservatively and discharged. After a week, she presented again with bilateral proptosis, chemosis, vision loss, and ophthalmoplegia, along with a characteristic lesion on the nose. A smear was prepared from the nasal lesion. What is the most appropriate initial management for a suspected fungal infection causing these symptoms?

Accepted Answer

Amphotericin B

Answer

Posaconazole

Answer

Itraconazole

Answer

Caspofungin

Question 6

Fever, clubbing, and Osler's nodes are characteristic findings in which of the following conditions?

Accepted Answer

Infective endocarditis

Answer

Typhoid fever

Answer

Rheumatic fever

Answer

Leptospirosis

Question 7

A 40-year-old man presents with fever, weight loss, and cough. His Mantoux test result is 18 x 19 mm, and sputum cytology is negative for Acid-Fast Bacilli (AFB). What is the most likely condition?

Accepted Answer

Pulmonary Tuberculosis

Answer

Pneumococcal Pneumonia

Answer

Cryptococcal Infection

Answer

Viral Infection

Question 8

A 68-year-old woman presents with new symptoms of burning when voiding. She has no fever, chills, or back discomfort. Her urinalysis reveals numerous white cells and bacteria. Which of the following medical comorbidities is most likely to coexist in this patient?

Accepted Answer

diabetes mellitus

Answer

anemia

Answer

exercise

Answer

influenza

Question 9

A 35-year-old male patient with a known case of HIV on Antiretroviral Therapy complains of fever, dyspnea, dry cough, and weight loss for the past 3 months. The chest X-ray of the patient is as below. What is your diagnosis?

Accepted Answer

Pneumocystis pneumonia

Answer

Staphylococcal pneumonia

Answer

Viral pneumonia

Answer

None of the above

Question 10

A 22-year-old male military recruit complains of a headache and stiff neck. He is examined, blood is drawn, and a lumbar puncture is performed. The glucose in the CSF is 100 mg/dL and the serum glucose is 120 mg/dL. The CSF shows 3 lymphocytes and 0 neutrophils/microliter. Which of the following conclusions concerning the interpretation of these findings is most accurate?

Accepted Answer

There is no evidence for meningitis

Answer

The CSF glucose level suggests bacterial meningitis

Answer

The CSF glucose level suggests viral meningitis

Answer

The lymphocytes suggest bacterial meningitis

Infectious Diseases — MCQs

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