Infectious Diseases Practice Questions

Q: A 26-year-old man is positive for HBsAg but negative for HBeAg. His AST and ALT levels are within normal limits. What is the next step in the management of this patient?

Serial monitoring. ### Explanation The patient is in the **Inactive HBsAg Carrier State** (also known as the Immune Control phase). This is characterized by the presence of HBsAg for >6 months, HBeAg negativity, anti-HBe positivity, and persistently normal ALT/AST levels. **1. Why Serial Monitoring is Correct:** In the inactive carrier state, the viral load is typically very low (HBV DNA <2,000 IU/mL) and there is minimal to no hepatic inflammation or fibrosis. According to AASLD and EASL guidelines, these patients do **not** require immediate antiviral therapy. Instead, they require **serial monitoring** (ALT every 3–6 months and HBV DNA periodically) to detect potential reactivation or progression to HBeAg-negative chronic hepatitis. **2. Why the Other Options are Incorrect:** * **Options B, C, & D:** Antiviral therapy (Interferon or Nucleoside analogs) is indicated only when there is evidence of active liver disease, characterized by **elevated ALT** (≥2x upper limit of normal) or **high viral load** (HBV DNA >2,000 IU/mL for HBeAg-negative patients) with significant fibrosis. * **Lamivudine Monotherapy (B):** Even if treatment were indicated, Lamivudine is no longer a first-line agent due to its high rate of resistance. Tenofovir or Entecavir are preferred. **Clinical Pearls for NEET-PG:** * **HBsAg (+):** Indicates infection (Acute or Chronic). * **HBeAg (+):** Indicates high infectivity and active viral replication. * **Normal ALT + HBsAg (+):** Usually implies either the "Immune Tolerant" phase (HBeAg positive, very high DNA) or the "Inactive Carrier" phase (HBeAg negative, low DNA). Neither typically requires immediate treatment. * **Goal of Monitoring:** To catch the transition to **HBeAg-negative Chronic Hepatitis**, where ALT rises and DNA levels increase despite being HBeAg negative (often due to precore/core promoter mutations).

Q: What is the immediate treatment of choice for severe hypotension in Dengue shock syndrome?

Intravenous crystalloids. ### Explanation **Correct Option: A. Intravenous crystalloids** The primary pathophysiology of Dengue Shock Syndrome (DSS) is **increased vascular permeability** leading to plasma leakage. This results in profound hypovolemia and hemoconcentration. The immediate treatment of choice is rapid volume replacement with **Isotonic Crystalloids** (e.g., Normal Saline or Ringer’s Lactate). The goal is to restore effective circulating volume and improve tissue perfusion. According to WHO guidelines, fluid resuscitation should be titrated based on the patient's clinical response and hematocrit levels. **Why Incorrect Options are Wrong:** * **B. Dexamethasone:** Steroids have no proven role in the management of Dengue or DSS. They do not reduce plasma leakage or improve survival and may increase the risk of gastrointestinal bleeding. * **C & D. Noradrenaline/Dopamine:** Inotropes and vasopressors are not the first-line treatment for DSS. The hypotension is **hypovolemic**, not cardiogenic or distributive. Using vasopressors in an "empty" vascular bed can worsen tissue ischemia. They are only considered in refractory shock after adequate fluid resuscitation has failed. **High-Yield Clinical Pearls for NEET-PG:** * **Critical Period:** The risk of DSS is highest during the **defervescence phase** (when the fever drops), usually between days 3–7 of illness. * **Fluid Choice:** Isotonic crystalloids are first-line. **Colloids** (e.g., Dextran 40 or Starch) are reserved for patients with refractory shock or those who do not respond to initial crystalloid boluses. * **Warning Signs:** Abdominal pain, persistent vomiting, mucosal bleed, lethargy, and a sudden increase in hematocrit with a rapid decrease in platelet count. * **Narrow Pulse Pressure:** A pulse pressure of **≤ 20 mmHg** is a hallmark sign of impending shock in Dengue.

Q: A male patient is HBsAg positive, HBeAg negative, and anti-HBe antibody positive. HBV DNA copies are 100,000/mL, and SGOT and SGPT are elevated to 6 times the upper limit of normal. What is the likely diagnosis?

HBV precore mutant. The clinical presentation describes a patient with active chronic hepatitis B who lacks the HBeAg marker. This is the classic profile of an **HBV Precore Mutant** infection [1]. 1. **Why the correct answer is right:** In "wild-type" HBV infection, the presence of HBeAg signifies high viral replication. However, a mutation in the **precore region** (most commonly a G-to-A substitution at nucleotide 1896) creates a stop codon that prevents the synthesis of HBeAg. Despite the absence of HBeAg and the presence of anti-HBe antibodies, the virus continues to replicate efficiently [1]. This is evidenced here by the high **HBV DNA (100,000 copies/mL)** and significant liver injury (**ALT/AST 6x normal**). 2. **Why the incorrect options are wrong:** * **HBV Surface Mutant:** This involves mutations in the 'a' determinant of HBsAg (e.g., G145R). It allows the virus to escape detection by standard HBsAg assays or vaccine-induced antibodies, but it does not specifically explain the HBeAg-negative/DNA-high discordance. * **Wild HBsAg:** In a typical wild-type active infection, high viral DNA and elevated enzymes would almost always be accompanied by a **positive HBeAg**. * **Inactive HBV Carrier:** While these patients are HBeAg negative and anti-HBe positive, they must have **low HBV DNA** ( 2,000 IU/mL and transaminases are elevated. * **Core Promoter Mutant:** Another variant (A1762T, G1764A) that decreases HBeAg production but increases viral replication. * **Treatment:** Precore mutants often have a more severe clinical course and higher rates of progression to cirrhosis compared to HBeAg-positive patients [1].

Q: What is the drug of choice for cerebral malaria?

Artesunate. **Explanation:** **1. Why Artesunate is the Correct Answer:** Intravenous (IV) **Artesunate** is currently the **Drug of Choice (DOC)** for severe malaria, including cerebral malaria, as recommended by both the WHO and National Guidelines (NVBDCP). It belongs to the Artemisinin class, which acts by releasing free radicals that damage the parasite's membrane. Artesunate is preferred over Quinine because it: * Acts faster on all erythrocytic stages (including younger ring forms). * Reduces parasite biomass more rapidly. * Has a better safety profile (lower risk of hypoglycemia and QT prolongation compared to Quinine). **2. Why the Other Options are Incorrect:** * **Chloroquine (A):** Historically the DOC for uncomplicated malaria, but it is no longer used for cerebral malaria due to widespread *Plasmodium falciparum* resistance. * **Primaquine (C):** This is used for the radical cure of *P. vivax* and *P. ovale* (to kill hypnozoites in the liver) or as a gametocidal agent. It has no role in the acute management of cerebral malaria. * **Sulfadoxine (D):** Usually combined with Pyrimethamine (S/P), it is a slow-acting antimalarial used in ACT combinations for uncomplicated malaria, not for life-threatening severe cases. **3. High-Yield Clinical Pearls for NEET-PG:** * **Loading Dose:** IV Artesunate is given at 2.4 mg/kg at 0, 12, and 24 hours, then once daily. * **Transition:** Once the patient can tolerate oral medication, a full 3-day course of **ACT (Artemisinin-based Combination Therapy)** must be completed. * **Side Effect:** Watch for **Delayed Hemolytic Anemia** (Post-Artesunate Hemolysis) 1–3 weeks after treatment. * **Pregnancy:** IV Artesunate is the DOC for severe malaria in **all trimesters** of pregnancy.

Q: Which statement is FALSE regarding Tuberculosis in an HIV-positive individual?

Cavitation lesions in the lungs as shown by chest X-ray.. **Explanation:** The presentation of Tuberculosis (TB) in HIV-positive patients is heavily dependent on the degree of immunosuppression (CD4 count). **Why Option D is the Correct (False) Statement:** Cavitation is a result of a robust cell-mediated immune response where the body attempts to wall off the infection, leading to caseous necrosis and tissue destruction. In HIV-positive individuals, especially those with low CD4 counts, the immune system is too weak to mount this hypersensitivity response. Consequently, **atypical chest X-ray findings** are common; patients often show lower lobe infiltrates, hilar lymphadenopathy, or even normal X-rays, while **cavitation is characteristically absent.** **Analysis of Other Options:** * **Option A (True):** Sputum smears are frequently negative because the lack of cavitation means fewer bacilli are discharged into the airways. * **Option B (True):** The Tuberculin Skin Test (TST/Mantoux) relies on a Delayed-Type Hypersensitivity (DTH) response. Due to T-cell depletion in HIV, patients often exhibit **anergy**, leading to false-negative results. * **Option C (True):** As immunity declines, the body fails to contain the primary infection, leading to hematogenous spread. This results in a much higher incidence of extrapulmonary (e.g., lymph nodes, CNS) and disseminated (miliary) TB. **NEET-PG High-Yield Pearls:** 1. **Diagnosis:** Since smear microscopy is often negative, **CBNAAT (GeneXpert)** is the preferred initial diagnostic test for TB in HIV patients. 2. **IRIS:** Starting ART in a TB patient can lead to **Immune Reconstitution Inflammatory Syndrome**, where the recovering immune system causes an exaggerated inflammatory response to TB antigens. 3. **Treatment:** Rifampicin is a potent inducer of CYP450; therefore, Efavirenz is the preferred NNRTI as it has fewer interactions compared to Protease Inhibitors.

Q: A patient with HIV and a CD4 count of 160 cells/µL presents with fever, cough, and shortness of breath for 3 weeks. Chest X-ray and silver staining of bronchoalveolar lavage are shown. What is the drug of choice for the causative organism?

Cotrimoxazole. ***Cotrimoxazole*** - The clinical picture of **HIV patient** with **CD4 <200 cells/µL**, subacute respiratory symptoms, and **silver staining** showing characteristic **Pneumocystis jirovecii cysts** in BAL confirms **Pneumocystis pneumonia (PCP)**. - **Cotrimoxazole (TMP-SMX)** is the **first-line drug of choice** for both treatment and prophylaxis of PCP in immunocompromised patients. *Azithromycin* - This **macrolide antibiotic** is effective against **atypical bacteria** like Mycoplasma and Chlamydia, but has **no activity against Pneumocystis jirovecii**. - Commonly used for **community-acquired pneumonia** and **MAC prophylaxis** in HIV patients, but not for PCP treatment. *Vancomycin* - This **glycopeptide antibiotic** is specifically used for **gram-positive bacterial infections**, particularly **MRSA** and other resistant organisms. - Has **no antifungal activity** and is ineffective against **Pneumocystis jirovecii**, which is a fungal pathogen. *Gentamicin* - This **aminoglycoside antibiotic** is primarily effective against **gram-negative bacteria** and some gram-positive organisms. - Has **no antifungal properties** and would be completely ineffective against **Pneumocystis jirovecii** pneumonia.

Question 1

A 26-year-old man is positive for HBsAg but negative for HBeAg. His AST and ALT levels are within normal limits. What is the next step in the management of this patient?

Accepted Answer

Serial monitoring

Answer

Antiviral treatment with Lamivudine monotherapy

Answer

Antiviral treatment with Lamivudine and pulsed Interferon

Answer

Antiviral treatment with Interferon Alfa alone

Question 2

What is the immediate treatment of choice for severe hypotension in Dengue shock syndrome?

Accepted Answer

Intravenous crystalloids

Answer

Dexamethasone

Answer

Noradrenaline

Answer

Dopamine

Question 3

A male patient is HBsAg positive, HBeAg negative, and anti-HBe antibody positive. HBV DNA copies are 100,000/mL, and SGOT and SGPT are elevated to 6 times the upper limit of normal. What is the likely diagnosis?

Accepted Answer

HBV precore mutant

Answer

HBV surface mutant

Answer

Wild HBsAg

Answer

Inactive HBV carrier

Question 4

What is the recommended duration of Miltefosine treatment for kala azar?

Accepted Answer

4 weeks

Answer

1 week

Answer

2 weeks

Answer

3 weeks

Question 5

A patient presents with fever for 5 days, altered sensorium, increased JVP, maculopapular rash, and erythema on the back with black necrotic tissue. What is the appropriate initial treatment?

Accepted Answer

Aminoglycosides

Answer

Chloramphenicol

Answer

Tetracycline

Answer

Doxycycline

Question 6

A 67-year-old man presents with persistent shooting pains, lower limb ataxia, and bladder dysfunction. Physical examination reveals small, irregular pupils that constrict with accommodation but not in response to light. A VDRL test is positive. A CT scan of the spinal cord would most likely demonstrate atrophy of which of the following structures?

Accepted Answer

Dorsal column

Answer

Dorsal horn

Answer

Lateral column

Answer

Ventral column

Question 7

A 26-year-old woman presents with a 5-day history of fever. On physical examination, her temperature is 38.2°C, pulse is 100/min, respirations are 19/min, and blood pressure is 90/60 mm Hg. A cardiac murmur is heard on auscultation. Her sensorium is clouded, but there are no focal neurologic deficits. Laboratory findings include hemoglobin, 13.1 g/dL; platelet count, 233,300/mm³; and WBC count, 19,200/mm³. Blood cultures are positive for gram-positive bacteria. Urinalysis shows hematuria. An echocardiogram reveals 1.5-cm vegetation on the mitral valve. Which of the following complications is this patient most likely to develop?

Accepted Answer

Cerebral arterial mycotic aneurysm

Answer

Dilated cardiomyopathy

Answer

Myxomatous mitral valve degeneration

Answer

Pericardial effusion with tamponade

Question 8

What is the drug of choice for cerebral malaria?

Accepted Answer

Artesunate

Answer

Chloroquine

Answer

Primaquine

Answer

Sulfadoxine

Question 9

Which statement is FALSE regarding Tuberculosis in an HIV-positive individual?

Accepted Answer

Cavitation lesions in the lungs as shown by chest X-ray.

Answer

Frequent negative sputum smear.

Answer

False negative tuberculin test result.

Answer

Extrapulmonary tuberculosis is more common.

Question 10

A patient with HIV and a CD4 count of 160 cells/µL presents with fever, cough, and shortness of breath for 3 weeks. Chest X-ray and silver staining of bronchoalveolar lavage are shown. What is the drug of choice for the causative organism?

Accepted Answer

Cotrimoxazole

Answer

Azithromycin

Answer

Vancomycin

Answer

Gentamicin

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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