Infectious Diseases Practice Questions

Q: Ibalizumab was approved by the FDA in April 2018 for which condition?

HIV. **Explanation:** **Ibalizumab** is a breakthrough medication in the management of **Human Immunodeficiency Virus (HIV)**. It is a humanized monoclonal antibody that acts as a **post-attachment inhibitor**. Unlike other entry inhibitors (like Maraviroc), Ibalizumab binds to the extracellular domain 2 of the **CD4+ T-cell receptor** [1]. This binding creates a conformational change that prevents the HIV-1 gp120 molecule from interacting with co-receptors (CCR5 or CXCR4), thereby blocking viral entry into the host cell. It was FDA-approved in 2018 specifically for **multidrug-resistant (MDR) HIV-1** in treatment-experienced adults failing their current antiretroviral regimen [1]. **Analysis of Incorrect Options:** * **Tuberculosis (TB):** TB is caused by *Mycobacterium tuberculosis* and is treated with antibiotics (RIPE regimen). Monoclonal antibodies are not currently a standard of care for TB. * **Leprosy:** Caused by *Mycobacterium leprae*, it is managed with Multi-Drug Therapy (MDT) involving Rifampicin, Dapsone, and Clofazimine. * **Malaria:** Caused by *Plasmodium* parasites, treatment involves antimalarials like Artemisinin-based combination therapies (ACTs) or Chloroquine. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Administration:** Ibalizumab is administered **intravenous (IV)** every 14 days, making it unique among HIV medications. * **Mechanism:** It does not cause immunosuppression because it does not interfere with MHC II molecule binding or CD4-mediated immune responses. * **Indication:** Reserved for "Salvage Therapy" in patients with limited options due to extensive drug resistance [1]. * **Other Entry Inhibitors:** Remember **Enfuvirtide** (Fusion inhibitor - binds gp41) and **Maraviroc** (CCR5 antagonist) [1].

Q: Which statement is not true regarding dengue hemorrhagic fever?

Shock. **Explanation:** The diagnosis of **Dengue Hemorrhagic Fever (DHF)** is defined by a specific triad of clinical and laboratory findings. According to the WHO criteria, DHF is characterized by fever, bleeding manifestations, **thrombocytopenia**, and evidence of **plasma leakage** [1]. **Why Option A is the Correct Answer:** While shock is a severe complication of dengue, it is the defining feature of **Dengue Shock Syndrome (DSS)**, not DHF. DHF is categorized into four grades (I to IV). Grades I and II represent DHF without shock, while Grades III and IV represent DSS [1]. Therefore, shock is not a mandatory requirement for a diagnosis of DHF. **Analysis of Incorrect Options:** * **B. Thrombocytopenia:** This is a mandatory criterion for DHF. A platelet count of ** 20% rise in hematocrit, pleural effusion, or ascites. **High-Yield Clinical Pearls for NEET-PG:** * **Critical Phase:** Usually occurs during days 3–7 of illness (defervescence), which is when plasma leakage and shock are most likely to develop [1]. * **Tourniquet Test:** A positive test (≥10 petechiae per square inch) suggests capillary fragility, common in DHF [1]. * **Most common cause of death:** Hypovolemic shock due to plasma leakage. * **Vector:** *Aedes aegypti* (Day biter).

Q: One day after a casual sexual encounter with a bisexual man recently diagnosed as antibody-positive for human immunodeficiency virus (HIV), a patient is concerned about whether she may have become infected. A negative antibody titer is obtained. To test for seroconversion, when is the earliest repeat antibody testing should be scheduled after the sexual encounter?

6 to 12 weeks. ### Explanation **Correct Option: C (6 to 12 weeks)** The primary concept here is the **"Window Period."** This is the interval between the initial HIV infection and the time when the body produces enough antibodies to be detected by standard screening tests (ELISA) [1]. While modern 4th-generation assays (which detect both p24 antigen and antibodies) can detect infection as early as 2–3 weeks, the traditional **antibody-only seroconversion** typically occurs within **6 to 12 weeks** in the vast majority of patients. By 3 months (12 weeks), more than 95% of individuals will have detectable antibodies [3]. Therefore, to reliably confirm or rule out seroconversion via antibody testing, the earliest recommended window starts at 6 weeks [3]. **Analysis of Incorrect Options:** * **A (1 to 2 weeks):** This is too early for an antibody response. Only HIV-RNA (viral load) via PCR might be detectable at this stage [2]. * **B (3 to 4 weeks):** While a 4th-generation p24 antigen test might be positive, an **antibody-only** titer (as specified in the question) is often still negative during this period. * **D (12 to 15 weeks):** While testing at this stage is highly accurate, it is not the *earliest* time to schedule a repeat test. 6 to 12 weeks is the standard diagnostic window [3]. **NEET-PG High-Yield Pearls:** 1. **Order of Detection:** Viral RNA (10–12 days) → p24 Antigen (14–16 days) → Antibodies (3–12 weeks). 2. **Screening Test:** ELISA (High sensitivity) [1]. 3. **Confirmatory Test:** Western Blot (detects antibodies to specific proteins like gp41, gp120, p24) [1]. *Note: Newer algorithms use HIV-1/2 differentiation assays.* 4. **Post-Exposure Prophylaxis (PEP):** Must be started within **72 hours** of exposure and continued for 28 days (Tenofovir + Emtricitabine + Dolutegravir/Raltegravir).

Q: What is the topical antifungal used in the treatment of Tinea corporis?

Tolnaftate. **Explanation:** **Tinea corporis** (ringworm) is a superficial dermatophyte infection of the glabrous skin [1]. The primary goal of treatment for localized, non-extensive lesions is the use of **topical antifungal agents** [1][2]. **1. Why Tolnaftate is Correct:** **Tolnaftate** is a topical thiocarbamate antifungal. It works by inhibiting the enzyme **squalene epoxidase**, which is essential for ergosterol synthesis in fungal cell membranes. It is highly effective against dermatophytes (Trichophyton, Microsporum, and Epidermophyton) and is a standard over-the-counter topical treatment for uncomplicated Tinea corporis. **2. Why the Other Options are Incorrect:** * **Itraconazole (B) and Fluconazole (C):** These are systemic triazoles [2]. While highly effective, they are reserved for extensive disease, tinea capitis, tinea unguium (onychomycosis), or cases refractory to topical therapy [2]. In the context of "topical antifungal used," these do not fit as they are primarily administered orally [2]. * **Griseofulvin (D):** This is an oral fungistatic agent that binds to tubulin, interfering with microtubule function. It is never used topically and is primarily indicated for Tinea capitis in children. **Clinical Pearls for NEET-PG:** * **First-line Topical Agents:** Terbinafine (Allylamine) is often considered more effective than Tolnaftate or Azoles due to its fungicidal properties. * **Steroid Warning:** Avoid topical steroids (e.g., Clobetasol) in Tinea; it leads to **Tinea Incognito**, where the classic annular morphology is lost, but the infection worsens [1]. * **Diagnosis:** The gold standard for bedside diagnosis is **KOH mount**, showing translucent, septate branching hyphae. * **Drug of Choice (Systemic):** Oral Terbinafine is currently the preferred systemic agent for dermatophytosis over Griseofulvin.

Q: What is the cornerstone treatment for dengue fever with warning signs, in the absence of shock or hemorrhage?

Intravenous fluids. The cornerstone of management for dengue fever with warning signs is **Intravenous (IV) fluid therapy**. The pathophysiology of severe dengue is characterized by increased capillary permeability leading to plasma leakage. This results in hemoconcentration and potential hypovolemic shock [1]. Administering isotonic crystalloids (like Normal Saline or Ringer’s Lactate) counteracts this leakage, maintains intravascular volume, and prevents progression to Dengue Shock Syndrome (DSS) [1]. **Analysis of Incorrect Options:** * **A. Platelet transfusion:** This is not indicated based on platelet count alone. It is reserved for patients with significant bleeding or very low counts (<10,000/mm³) with high risk of hemorrhage. Prophylactic transfusion does not improve outcomes. * **C. Cryoglobulins:** These have no role in the management of dengue. Cryoprecipitate may be used in rare cases of disseminated intravascular coagulation (DIC), but it is not a primary treatment. * **D. Antivirals:** There are currently no approved or effective antiviral drugs for the treatment of Dengue virus; management remains purely supportive. **High-Yield Clinical Pearls for NEET-PG:** * **Warning Signs:** Abdominal pain/tenderness, persistent vomiting, mucosal bleed, lethargy, liver enlargement >2cm, and a rapid increase in Hct with a rapid decrease in platelet count. * **Fluid Choice:** Isotonic crystalloids are the first choice. Colloids are reserved for refractory shock. * **Critical Period:** Usually occurs between days 3–7 of illness during the "defervescence" phase (when fever drops) [1]. This is when plasma leakage is most severe. * **Avoid:** NSAIDs (like Aspirin/Ibuprofen) due to the risk of bleeding; use Paracetamol for fever.

Q: Which of the following is a chronic complication of malaria?

Both nephrotic syndrome and splenomegaly. The correct answer is Both nephrotic syndrome and splenomegaly because chronic or repeated exposure to malaria parasites leads to persistent immune activation and structural organ changes. 1. Nephrotic Syndrome: This is a classic chronic complication specifically associated with Plasmodium malariae. It results from the deposition of immune complexes in the glomerular basement membrane (Quartan Malarial Nephropathy). Unlike the acute kidney injury seen in P. falciparum, this is a chronic, progressive condition that often responds poorly to antimalarial therapy. 2. Splenomegaly: Chronic or recurrent malaria leads to persistent congestion and hyperplasia of the reticuloendothelial system [1]. A specific chronic manifestation is Hyperreactive Malarial Splenomegaly (HMS), formerly known as Tropical Splenomegaly Syndrome. It is characterized by massive splenomegaly, high titers of anti-malarial antibodies, and hypergammaglobulinemia (IgM). Why other options are incorrect: * Pneumonia: While pulmonary edema and ARDS are severe acute complications of P. falciparum malaria, pneumonia is typically a secondary bacterial superinfection rather than a direct chronic complication of the malaria parasite itself. High-Yield Clinical Pearls for NEET-PG: * HMS Treatment: Long-term antimalarial chemoprophylaxis (e.g., Proguanil or Chloroquine) is the treatment of choice for Hyperreactive Malarial Splenomegaly. * Blackwater Fever: An acute complication involving massive intravascular hemolysis and hemoglobinuria, usually associated with P. falciparum and quinine use. * Recrudescence vs. Relapse: P. falciparum causes recrudescence (sub-optimal treatment) [1], while P. vivax and P. ovale cause relapse due to hypnozoites in the liver [1].

Q: A 32-year-old woman seeking to become pregnant visits her physician for a pre-pregnancy examination. Routine prenatal laboratory testing demonstrates the following profile: HBsAg (-), anti-HBsAg (+), anti-HBcAg (-), anti-HBeAg (-), and HBV DNA (-). Which of the following likely represents the status of the patient?

Immunized against hepatitis B. ### Explanation The patient’s serological profile indicates immunity acquired through **vaccination**. **1. Why the Correct Answer is Right:** The presence of **anti-HBsAg (+)** in the absence of other markers is the hallmark of successful immunization. * **HBsAg (-):** Indicates no active infection [1]. * **Anti-HBsAg (+):** Indicates protective immunity. * **Anti-HBcAg (-):** This is the "crucial differentiator." Anti-HBc (Antibody to Core antigen) is only produced in response to an actual viral infection (natural infection). Since vaccines contain only the recombinant surface protein (HBsAg) and no core components, a vaccinated person will be **Anti-HBc negative** [1]. **2. Why the Other Options are Wrong:** * **Option A (Carrier):** A chronic carrier would be **HBsAg (+)** for more than 6 months and **Anti-HBc (+)** (IgG) [1]. * **Option C (Window Period):** During the "window period," HBsAg has disappeared but Anti-HBs has not yet appeared. The only marker typically positive is **Anti-HBc IgM** [1]. * **Option D (Highly Transmissible):** High infectivity is characterized by the presence of **HBsAg (+)** and **HBeAg (+)**, along with high levels of **HBV DNA**. **3. NEET-PG High-Yield Pearls:** * **Natural Infection (Recovered):** HBsAg (-), **Anti-HBc (+)**, Anti-HBs (+) [1]. * **Vaccinated:** HBsAg (-), **Anti-HBc (-)**, Anti-HBs (+). * **HBeAg:** Represents active viral replication and high infectivity. * **Anti-HBs Titer:** A level of **≥10 mIU/mL** after a 3-dose vaccine series is considered protective. * **Isolated Anti-HBc (+):** Can represent a "resolved" infection where Anti-HBs has waned, a "window period," or a false positive.

Question 1

Ibalizumab was approved by the FDA in April 2018 for which condition?

Accepted Answer

HIV

Answer

Tuberculosis (TB)

Answer

Leprosy

Answer

Malaria

Question 2

Which statement is not true regarding dengue hemorrhagic fever?

Accepted Answer

Shock

Answer

Thrombocytopenia

Answer

Hepatomegaly

Answer

Plasma leakage

Question 3

One day after a casual sexual encounter with a bisexual man recently diagnosed as antibody-positive for human immunodeficiency virus (HIV), a patient is concerned about whether she may have become infected. A negative antibody titer is obtained. To test for seroconversion, when is the earliest repeat antibody testing should be scheduled after the sexual encounter?

Accepted Answer

6 to 12 weeks

Answer

1 to 2 weeks

Answer

3 to 4 weeks

Answer

12 to 15 weeks

Question 4

What is the prophylactic antifungal drug commonly used in HIV patients?

Accepted Answer

Itraconazole

Answer

Posaconazole

Answer

Terconazole

Answer

Voriconazole

Question 5

What is the topical antifungal used in the treatment of Tinea corporis?

Accepted Answer

Tolnaftate

Answer

Itraconazole

Answer

Fluconazole

Answer

Griseofulvin

Question 6

A man from Mexico presents with a clinical finding that, upon biopsy, reveals the presence of gram-negative bacilli. What is the most likely causative agent?

Accepted Answer

Klebsiella rhinoscleromatis

Answer

Mycobacterium leprae

Answer

Acinetobacter baumannii

Answer

Treponema pallidum

Question 7

What is the cornerstone treatment for dengue fever with warning signs, in the absence of shock or hemorrhage?

Accepted Answer

Intravenous fluids

Answer

Platelet transfusion

Answer

Cryoglobulins

Answer

Antivirals

Question 8

Which of the following is a chronic complication of malaria?

Accepted Answer

Both nephrotic syndrome and splenomegaly

Answer

Pneumonia

Answer

Nephrotic syndrome

Answer

Splenomegaly

Question 9

Serology of a young man shows HBsAg, but HBeAg is negative with normal levels of AST and ALT. He is asymptomatic. What is the next line of management?

Accepted Answer

Wait and watch

Answer

Antiviral therapy

Answer

Immunoglobulins

Answer

Liver transplant

Question 10

A 32-year-old woman seeking to become pregnant visits her physician for a pre-pregnancy examination. Routine prenatal laboratory testing demonstrates the following profile: HBsAg (-), anti-HBsAg (+), anti-HBcAg (-), anti-HBeAg (-), and HBV DNA (-). Which of the following likely represents the status of the patient?

Accepted Answer

Immunized against hepatitis B

Answer

Hepatitis B carrier

Answer

Infected and within the window period

Answer

Infected with hepatitis B and highly transmissible

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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