Infectious Diseases Practice Questions

Q: Cryptococcal meningitis is most common in which of the following patient populations?

Renal transplant recipients. **Explanation:** **1. Why Renal Transplant Recipients is Correct:** *Cryptococcus neoformans* is an opportunistic encapsulated yeast that primarily affects patients with **defective cell-mediated immunity (CMI)** [1]. Renal transplant recipients are at high risk because their immunosuppressive regimen (e.g., corticosteroids, calcineurin inhibitors) specifically targets T-cell function. Among solid organ transplant recipients, *Cryptococcus* is the third most common invasive fungal infection and has a high predilection for the Central Nervous System (CNS) [1]. **2. Why Other Options are Incorrect:** * **B & D (Agammaglobulinemia and IgA deficiency):** These are **humoral (B-cell) immunity** defects. While antibodies play a minor role in opsonization, the primary defense against *Cryptococcus* is macrophage activation by T-helper cells (Th1 response). Patients with B-cell defects are more prone to sinopulmonary infections by encapsulated bacteria (e.g., *S. pneumoniae*). * **C (Neutropenia):** Neutrophils are the primary defense against molds like *Aspergillus* and *Mucor*. While neutrophils do participate in the early response to fungi, *Cryptococcus* is classically associated with T-cell deficits (HIV/AIDS, transplants, lymphomas) rather than isolated neutropenia. **Clinical Pearls for NEET-PG:** * **Most Common Cause:** *Cryptococcus* is the most common cause of fungal meningitis worldwide. * **Diagnosis:** The most sensitive screening test is the **Cryptococcal Antigen (CrAg)** in CSF or serum (Lateral Flow Assay). * **Microscopy:** **India Ink** preparation shows a "halolike" unstained capsule. * **Culture:** Grows on **Sabouraud Dextrose Agar (SDA)**; colonies appear creamy/mucoid. It is urease positive. * **Treatment:** Induction with **Amphotericin B + Flucytosine**, followed by maintenance with Fluconazole. * **CSF Finding:** Characteristically shows high opening pressure and low glucose.

Q: Which of the following conditions are associated with Hepatitis C Virus (HCV)?

Scleroderma. **Explanation:** Hepatitis C Virus (HCV) is unique among viral hepatitides for its strong association with various **extrahepatic manifestations**. **1. Why Scleroderma is the Correct Answer:** While HCV is classically associated with several autoimmune and rheumatological conditions, **Scleroderma (Systemic Sclerosis) is NOT typically associated with HCV.** In the context of this specific question (likely a "Which of the following is NOT associated" or "Except" style question common in NEET-PG), Scleroderma stands out as the outlier. Most literature focuses on HCV's link to Sjögren’s syndrome or Lichen Planus rather than Scleroderma. **2. Analysis of Other Options:** * **Cryoglobulinemia (Option C):** This is the **most common** extrahepatic manifestation of HCV. Specifically, **Mixed Cryoglobulinemia (Type II and III)** occurs in up to 50% of HCV patients, leading to vasculitis, glomerulonephritis, and palpable purpura. * **Anti-LKM-1 antibody (Option A):** Anti-Liver Kidney Microsomal type 1 antibodies are the hallmark of **Autoimmune Hepatitis (Type 2)**. However, they are also found in a subset of patients with chronic HCV, making it a recognized association. * **Polyarteritis nodosa (Option D):** While PAN is classically and more strongly associated with **Hepatitis B (HBV)**, it has been documented in rare cases of HCV. However, in most competitive exams, if both HBV and HCV are options for PAN, HBV is the primary association. **High-Yield Clinical Pearls for NEET-PG:** * **HCV + Skin:** Porphyria Cutanea Tarda (PCT) and Lichen Planus [1]. * **HCV + Kidney:** Membranoproliferative Glomerulonephritis (MPGN). * **HCV + Endocrine:** Type 2 Diabetes Mellitus and Autoimmune Thyroiditis. * **HCV + Hematology:** B-cell Non-Hodgkin Lymphoma. * **Key Distinction:** Remember **PAN = HBV** and **Cryoglobulinemia = HCV**.

Q: All of the following are features of tetanus, except?

Loss of consciousness occurs in moderately advanced cases. The correct answer is **D**. In Tetanus, the sensorium remains **completely clear** until the very end [1]. The toxin, tetanospasmin, acts on the inhibitory interneurons (Renshaw cells) in the spinal cord and brainstem, but it does not affect the cerebral cortex. Therefore, patients remain fully conscious and alert, which adds to the distress of the painful muscle spasms. Loss of consciousness is not a feature of tetanus unless it occurs as a secondary complication of hypoxia or severe sedation. **Analysis of other options:** * **Option A (Vertebral fractures):** These are a known complication of generalized tetanus. The intense, violent muscular contractions (opisthotonus) can be powerful enough to cause compression fractures of the thoracic vertebrae. * **Option B (Recovery in 4 weeks):** Tetanospasmin binds irreversibly to neuronal receptors. Recovery requires the growth of new axonal nerve terminals, a process that typically takes **3 to 4 weeks**. Survivors usually recover completely unless secondary complications occur. * **Option C (Clinical Diagnosis):** Tetanus is a **clinical diagnosis**. *Clostridium tetani* is rarely recovered from the wound site (only 33% of cases), and its presence does not prove the disease [1]. Serum antitoxin levels are also not helpful for acute diagnosis. **Clinical Pearls for NEET-PG:** * **Pathogenesis:** Retrograde axonal transport of tetanospasmin; cleaves **SNARE proteins** (Synaptobrevin). * **Earliest Sign:** Trismus (Lockjaw) due to masseter spasm. * **Risus Sardonicus:** Characteristic "sneering" grin due to facial muscle spasm. * **Autonomic Dysfunction:** A major cause of death in modern ICUs (labile hypertension, tachycardia, hyperpyrexia). * **Management:** Metronidazole is the preferred antibiotic; Penicillin is avoided as it is a GABA antagonist and may worsen spasms.

Q: Procalcitonin is used as a marker of which condition?

Sepsis. **Explanation:** **Procalcitonin (PCT)** is a peptide precursor of the hormone calcitonin. In healthy individuals, it is produced by the C-cells of the thyroid gland and is present in negligible amounts in the blood (<0.1 ng/mL). **Why Sepsis is the Correct Answer:** In response to **systemic bacterial infections** and sepsis, PCT levels rise rapidly (within 2–4 hours). This occurs because inflammatory cytokines (like IL-6 and TNF-α) and bacterial endotoxins trigger the extra-thyroidal synthesis of PCT in various parenchymal tissues (liver, kidney, muscle). Crucially, PCT levels remain low during viral infections because Interferon-gamma (IFN-γ), produced in response to viruses, inhibits PCT synthesis. This makes it a highly specific marker for differentiating bacterial sepsis from non-infectious inflammation or viral illnesses. **Analysis of Incorrect Options:** * **Option A (Cardiac dysfunction):** Markers like **Troponins (I and T)** and **CK-MB** are used for myocardial infarction, while **BNP/NT-proBNP** are markers for cardiac failure. * **Option B (Menstrual periodicity):** This is regulated by the cyclical fluctuations of **FSH, LH, Estrogen, and Progesterone**. * **Option C (Pituitary function):** This is assessed using specific trophic hormones such as **ACTH, GH, TSH, and Prolactin**. **High-Yield Clinical Pearls for NEET-PG:** * **Half-life:** PCT has a half-life of approximately **24–35 hours**, making it useful for monitoring response to antibiotics. * **Antibiotic Stewardship:** Falling PCT levels are used clinically to decide when to de-escalate or stop antibiotic therapy. * **Prognostic Value:** Higher levels of PCT correlate with the severity of sepsis and increased mortality risk.

Q: All of the following are seen in active chronic hepatitis B except?

IgM against core antigen. In Hepatitis B serology, the presence of specific markers distinguishes between acute, chronic, and past infections. This is a high-yield topic for NEET-PG. **Explanation of the Correct Answer:** **Option A (IgM anti-HBc)** is the correct answer because it is a marker of **acute infection** [1]. It appears shortly after HBsAg and persists for about 6 months (the "window period") [1]. In **chronic hepatitis B** (defined by the persistence of HBsAg for >6 months), the immune response shifts from IgM to **IgG** [1]. Therefore, IgM anti-HBc is typically absent in chronic states, unless there is a severe acute flare-up. **Analysis of Incorrect Options:** * **Option B (Total core antibody):** This includes both IgM and IgG. Since IgG anti-HBc persists for life after exposure, total core antibody will be positive in both active chronic and recovered patients [1]. * **Option C (HBeAg):** This is a marker of active viral replication and high infectivity [1]. It is frequently seen in the "active" phase of chronic hepatitis B (HBeAg-positive chronic hepatitis) [1]. * **Option D (HBsAg):** This is the hallmark of any ongoing infection [1]. Its presence for more than 6 months is the defining diagnostic criterion for chronic hepatitis B [1]. **NEET-PG High-Yield Pearls:** 1. **Window Period:** The period where HBsAg and Anti-HBs are both negative; **IgM anti-HBc** is the only diagnostic marker [1]. 2. **Chronic Infection:** Defined by HBsAg (+) for >6 months [1]. 3. **Infectivity:** HBeAg correlates with high viral load and high risk of transmission [1]. 4. **Vaccination:** Only **Anti-HBs** will be positive; all other markers (Core/Envelope) will be negative [1].

Q: Which of the following antitubercular drugs is safe in hepatitis?

Ethambutol. ### Explanation The management of Tuberculosis in patients with pre-existing liver disease or drug-induced hepatitis requires a clear understanding of the metabolic pathways of Anti-Tubercular Treatment (ATT). [1] **1. Why Ethambutol is the Correct Answer:** Ethambutol is primarily excreted via the **kidneys (approx. 80%)** and does not undergo significant hepatic metabolism. Unlike other first-line drugs, it is **not hepatotoxic**. Therefore, it is considered the safest first-line agent to continue or initiate in patients with hepatitis or chronic liver disease. Streptomycin is the other first-line drug (injectable) that is safe in hepatitis as it is also renally excreted. **2. Why the Other Options are Incorrect:** The "Big Three" hepatotoxic drugs are: * **Pyrazinamide (C):** The **most hepatotoxic** drug among the first-line agents. It often causes prolonged or severe liver injury. * **Isoniazid (A):** Frequently causes a transient rise in transaminases; it is metabolized via acetylation in the liver. It is the second most hepatotoxic. [1] * **Rifampicin (B):** While it can cause hepatitis, it more commonly causes **asymptomatic cholestasis** (elevation of bilirubin) due to competition for excretion. It is the least hepatotoxic of these three but still contraindicated in acute hepatitis. **Clinical Pearls for NEET-PG:** * **Order of Hepatotoxicity:** Pyrazinamide > Isoniazid > Rifampicin. * **Safe Drugs in Liver Disease:** Ethambutol, Streptomycin, and Fluoroquinolones (like Levofloxacin). [1] * **Management Rule:** If AST/ALT levels are >3 times the upper limit of normal (with symptoms) or >5 times (without symptoms), hepatotoxic drugs must be stopped. [1] * **Reintroduction:** Once enzymes normalize, drugs are reintroduced one by one: Rifampicin first, followed by Isoniazid, and finally Pyrazinamide. [1]

Question 1

A 40-year-old male presented with altered mental status, seizures, and vomiting. He has no history of fever or neck stiffness. On CECT and MRI, a ring-enhancing lesion at the gray-white interface is seen. General hygiene was poor, and he has multiple dental caries. What is the next best step in the management of this patient?

Accepted Answer

Urgent parenteral antibiotics

Answer

Placement of ICP monitor

Answer

Lumbar puncture

Answer

Craniotomy

Question 2

Cryptococcal meningitis is most common in which of the following patient populations?

Accepted Answer

Renal transplant recipients

Answer

Patients with agammaglobulinemia

Answer

Patients with neutropenia

Answer

Patients with IgA deficiency

Question 3

Which of the following conditions are associated with Hepatitis C Virus (HCV)?

Accepted Answer

Scleroderma

Answer

Anti-LKM-1 antibody

Answer

Cryoglobulinemia

Answer

Polyarteritis nodosa

Question 4

All of the following are features of tetanus, except?

Accepted Answer

Loss of consciousness occurs in moderately advanced cases

Answer

Vertebral fractures

Answer

Survivors recover completely in 4 weeks

Answer

Diagnosis is clinical and no microbiological tests are required

Question 5

An elderly male develops fever 3 days after cholecystectomy. He becomes short of breath, and CXR shows a new right lower lobe infiltrate. Sputum Gram stain shows gram-positive cocci in clumps, and preliminary culture results suggest staphylococci. What is the initial antibiotic of choice?

Accepted Answer

Antibiotic therapy should be based on the incidence of methicillin-resistant staphylococci in that hospital

Answer

Nafcillin

Answer

Vancomycin

Answer

Quinolones are the drug of choice for pneumonia

Question 6

Procalcitonin is used as a marker of which condition?

Accepted Answer

Sepsis

Answer

Cardiac dysfunction in acute coronary syndrome

Answer

Menstrual periodicity

Answer

Pituitary function

Question 7

Kala-azar is not responding to primary treatment. What should be the next line of treatment?

Accepted Answer

Amphotericin-B

Answer

Double dose of antimony

Answer

Ketoconazole

Answer

Splenectomy

Question 8

All of the following are seen in active chronic hepatitis B except?

Accepted Answer

IgM against core antigen

Answer

Total core antibody

Answer

HbeAg

Answer

HbsAg

Question 9

A patient requires antibiotic treatment for culture-positive infective enterococcal endocarditis involving an artificial valve. The patient has a history of a severe anaphylactic reaction to penicillin G within the past year. What is the recommended treatment approach?

Accepted Answer

Vancomycin

Answer

Amoxicillin-clavulanic acid

Answer

Aztreonam

Answer

Cefazolin plus gentamicin

Question 10

Which of the following antitubercular drugs is safe in hepatitis?

Accepted Answer

Ethambutol

Answer

Isoniazid

Answer

Rifampicin

Answer

Pyrazinamide

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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