Infectious Diseases Practice Questions

Q: A 65-year-old woman undergoes a kidney transplant for CKD. Six weeks after the transplant, she develops CMV infection characterized by fever, malaise, and myalgias. Which of the following is a potential sequela of CMV infection?

GI ulcers and hemorrhage. **Explanation:** Cytomegalovirus (CMV) is the most common opportunistic viral infection in solid organ transplant recipients, typically manifesting within the first 1–6 months post-transplant due to peak immunosuppression. **Why Option D is Correct:** CMV has a particular tropism for vascular endothelial cells. In the gastrointestinal tract, it causes **endothelial damage and vasculitis**, leading to mucosal ischemia and subsequent **ulceration**. These ulcers are typically "punched-out" and can occur anywhere from the esophagus to the colon, leading to symptoms of odynophagia, abdominal pain, and significant **GI hemorrhage**. In renal transplant patients, CMV is also a major cause of graft dysfunction and "CMV syndrome" (fever and cytopenias). **Why Other Options are Incorrect:** * **Options A & B:** Intra-abdominal abscesses and pyelonephritis are typically **bacterial** complications (e.g., *E. coli*, *Klebsiella*). While transplant patients are at risk for these, they are not specific sequelae of CMV infection. * **Option C:** While CMV can rarely cause acalculous cholecystitis in advanced AIDS patients, it is not a classic or common sequela in the post-transplant period compared to GI involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for **"Owl’s eye" inclusion bodies** (large intranuclear inclusions with a clear halo). * **Diagnosis:** **pp65 antigenemia** assay or **PCR** for CMV DNA are the preferred diagnostic methods. * **Treatment:** **Ganciclovir** is the drug of choice; Valganciclovir is used for prophylaxis. * **Congenital CMV:** Most common cause of non-syndromic sensorineural hearing loss and periventricular calcifications.

Q: A 37-year-old female presents to the emergency room with a fever. Chest x-ray shows multiple patchy infiltrates in both lungs. Echocardiography and blood cultures suggest a diagnosis of acute bacterial endocarditis limited to the tricuspid valve. Which of the following is the most probable etiology?

Illicit drug use. The clinical presentation of **fever, multiple patchy lung infiltrates, and tricuspid valve endocarditis** is a classic triad for **Right-Sided Infective Endocarditis (RSIE)**. **1. Why Illicit Drug Use is Correct:** Intravenous drug use (IVDU) is the most significant risk factor for right-sided endocarditis [2]. When non-sterile needles are used, bacteria (most commonly *Staphylococcus aureus*) enter the venous system and first encounter the tricuspid valve [3]. The "patchy infiltrates" on the chest X-ray represent **septic pulmonary emboli**, which occur when infected vegetations break off the tricuspid valve and travel through the pulmonary artery into the lungs [1]. **2. Why Other Options are Incorrect:** * **Congenital Heart Disease (CHD):** While CHD (e.g., VSD, PDA) predisposes patients to endocarditis, it typically affects the left side or specific pressure-gradient sites. It is a less common cause of isolated tricuspid involvement compared to IVDU. * **Rheumatic Fever:** Chronic rheumatic heart disease predominantly affects the **Mitral valve** (most common) followed by the Aortic valve. Isolated tricuspid involvement is extremely rare in rheumatic cases. * **Rheumatoid Arthritis:** While RA can cause sterile valvular nodules or pericarditis, it is not a recognized cause of acute bacterial endocarditis. **3. NEET-PG High-Yield Pearls:** * **Most common organism in IVDU:** *Staphylococcus aureus* (often MRSA) [3]. * **Most common valve involved in IVDU:** Tricuspid Valve. * **Most common valve involved overall (Non-IVDU):** Mitral Valve. * **Radiological Hallmark:** Multiple peripheral wedge-shaped opacities or cavitary lesions (septic emboli) [1]. * **Clinical Sign:** A systolic murmur that increases with inspiration (**Carvallo’s sign**) suggests tricuspid regurgitation [2].

Q: What is true about miliary tuberculosis?

Commonly affects liver, kidney and spleen. **Explanation:** Miliary tuberculosis (TB) is a form of disseminated tuberculosis resulting from the **hematogenous (blood-borne) spread** of *Mycobacterium tuberculosis* [1]. **Why Option D is Correct:** When TB bacilli enter the bloodstream, they are filtered by the reticuloendothelial system. This leads to the formation of tiny, discrete foci of infection (1–2 mm granulomas resembling millet seeds) across multiple organs. The **liver, spleen, bone marrow, kidneys, and lungs** are the most frequently involved sites [1]. Clinical findings often include hepatosplenomegaly and lymphadenopathy [1]. **Analysis of Incorrect Options:** * **Options A, B, and C:** Miliary TB is not exclusive to a specific phase of the disease. It can occur during **primary infection** (early hematogenous spread before cell-mediated immunity is fully established) or as a result of **reactivation** of a latent focus (secondary TB) [1]. Because it can occur in both scenarios—and even as a result of direct iatrogenic vascular erosion—stating it occurs "following" only one specific type of reactivation is restrictive and technically inaccurate in this context. **High-Yield Clinical Pearls for NEET-PG:** * **Chest X-ray:** Shows a classic "millet seed" pattern (uniform 1–2 mm nodules) throughout both lung fields [1]. * **Choroid Tubercles:** Pathognomonic yellowish lesions on the retina (fundoscopy) are seen in ~30% of cases [1]. * **Diagnosis:** Gold standard is often a biopsy (liver or bone marrow) showing granulomas, or culture of body fluids. * **Auregnostic sign:** In elderly patients, "cryptic miliary TB" can present as a fever of unknown origin (FUO) without classic radiologic findings.

Q: Clinical features of anicteric Leptospirosis are all EXCEPT:

High mortality. **Explanation:** Leptospirosis is a zoonotic infection caused by *Leptospira interrogans*. It typically presents in two clinical forms: **Anicteric leptospirosis** (mild, 90% of cases) and **Icteric leptospirosis** (Weil’s disease, severe, 5–10% of cases). **Why "High Mortality" is the correct answer:** Anicteric leptospirosis is generally a self-limiting, mild disease with an **excellent prognosis and very low mortality**. High mortality (5–15% or higher) is characteristic of the **Icteric form (Weil’s disease)**, which involves hepatic failure (jaundice), renal failure, and pulmonary hemorrhage. **Analysis of Incorrect Options:** * **Option A (Influenza-like illness):** The septicemic phase of anicteric leptospirosis mimics the flu, presenting with sudden onset fever, chills, headache, and occasionally hepatosplenomegaly. * **Option B (Muscle pain):** Myalgia is a hallmark of leptospirosis, typically involving the calves, thighs, and lumbar region. It is often severe and associated with muscle tenderness. * **Option C (Conjunctival suffusion):** This is the **most characteristic and common physical finding**. It involves redness of the conjunctiva without inflammatory exudate (distinguishing it from viral/bacterial conjunctivitis). **High-Yield Clinical Pearls for NEET-PG:** 1. **Biphasic Nature:** Anicteric leptospirosis has two phases: the *Septicemic phase* (Leptospira in blood/CSF) and the *Immune phase* (Leptospira in urine; may present as aseptic meningitis). 2. **Weil’s Disease Triad:** Jaundice, Renal failure, and Hemorrhage. 3. **Diagnosis:** **MAT (Microscopic Agglutination Test)** is the Gold Standard. 4. **Treatment:** Doxycycline is the drug of choice for mild cases; IV Penicillin G for severe cases. Doxycycline is also used for prophylaxis.

Q: A 6-year-old child presents with perianal pruritus, skin excoriation, and nocturnal enuresis, and is found to be infected with a parasite capable of autoinfection. What is the infective form of this parasite for humans?

Embryonated egg. ### Explanation **Diagnosis:** The clinical presentation of **perianal pruritus** (worse at night), skin excoriation, and **nocturnal enuresis** in a child is classic for **Enterobius vermicularis** (Pinworm/Seatworm). **1. Why the Correct Answer is Right:** The life cycle of *E. vermicularis* begins when the gravid female migrates to the perianal skin at night to deposit eggs. These eggs become **embryonated (infective)** within 4 to 6 hours. Infection occurs via the fecal-oral route when these embryonated eggs are ingested. The parasite is unique because it can cause **retro-infection** (larvae hatch on the perianal skin and migrate back into the colon) and **autoinfection** (hand-to-mouth transfer due to scratching), both of which involve the embryonated egg as the starting point of the cycle. **2. Why Incorrect Options are Wrong:** * **A. Filariform larvae:** This is the infective stage for *Strongyloides stercoralis*, *Ancylostoma duodenale*, and *Necator americanus* [1]. While *Strongyloides* also causes autoinfection, it presents with "larva currens" (transient itchy linear weals) and respiratory/GI symptoms rather than isolated perianal pruritus [1]. * **C & D. Adult female/male:** Adult worms live in the cecum and appendix. While the migrating female causes the symptoms, the adult stage is not the mode of transmission or the infective form for humans. **3. NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** NIH Swab or **Scotch Tape Test** (Cellophane tape test) performed early in the morning. Eggs are typically not found in routine stool exams. * **Morphology:** Eggs are characteristic **"D-shaped"** (planoconvex) and possess a double-layered shell. * **Treatment:** Albendazole or Mebendazole (single dose, repeated after 2 weeks). **Treat the entire family** to prevent reinfection. * **Associated Condition:** Pinworms are a known (though rare) cause of acute appendicitis in children.

Q: A laboratory technician was accidentally exposed to an HIV-seropositive serum sample. What is the role of zidovudine in the post-exposure prophylaxis for this patient?

To prevent acquisition of HIV infection.. ### Explanation **Correct Option: A (To prevent acquisition of HIV infection)** The primary goal of Post-Exposure Prophylaxis (PEP) is to prevent the establishment of a systemic viral infection following accidental exposure [1]. When a person is exposed to HIV, the virus takes time to disseminate from the site of entry to the regional lymph nodes and eventually the bloodstream [2]. Administering antiretroviral drugs like **Zidovudine** (an NRTI) inhibits viral replication during this critical "window period," effectively preventing the virus from integrating into the host genome and establishing a permanent infection. **Analysis of Incorrect Options:** * **Option B:** Seronegativity refers to the absence of antibodies. While PEP prevents infection (and thus prevents the patient from ever becoming seropositive), the *purpose* of the drug is to stop the virus, not to manipulate antibody test results. * **Option C:** Delaying disease progression is the goal of Highly Active Antiretroviral Therapy (HAART) in patients who are **already** HIV-positive. In the context of PEP, the aim is "prevention," not "management" of a chronic state. **NEET-PG High-Yield Pearls:** 1. **Timing:** PEP should be started as soon as possible, ideally within **2 hours**, and no later than **72 hours** post-exposure [1]. 2. **Duration:** The standard duration for PEP is **28 days**. 3. **Current Regimen:** While Zidovudine was historically the mainstay, current NACO/WHO guidelines prefer a three-drug regimen (e.g., **Tenofovir + Lamivudine + Dolutegravir**). 4. **Risk of Transmission:** The average risk of HIV transmission after a percutaneous needle-stick injury is approximately **0.3%** [2].

Q: A patient presents with high-grade fever and altered sensorium, and is diagnosed with meningococcal meningitis. Which of the following is the most appropriate empirical treatment?

Ceftriaxone. **Explanation:** **Ceftriaxone (Option A)** is the drug of choice for the empirical treatment of meningococcal meningitis. The primary reason is its **excellent cerebrospinal fluid (CSF) penetration**, even when meninges are inflamed, and its high potency against *Neisseria meningitidis*. Unlike Penicillin, Ceftriaxone has a long half-life (allowing once or twice-daily dosing) and covers potential co-pathogens like *Streptococcus pneumoniae* and *Haemophilus influenzae*. **Why other options are incorrect:** * **Penicillin (Option C):** While historically the drug of choice for confirmed sensitive strains, it is no longer used **empirically** due to the global rise of penicillin-resistant *S. pneumoniae* and the requirement for frequent intravenous dosing. * **Piperacillin-Tazobactam (Option B):** This is a broad-spectrum antipseudomonal penicillin. However, it has **poor CNS penetration** and is not indicated for community-acquired meningitis. * **Cotrimoxazole (Option D):** It is not a first-line agent for acute bacterial meningitis due to inferior bactericidal activity compared to third-generation cephalosporins. **High-Yield Clinical Pearls for NEET-PG:** * **Chemoprophylaxis:** For close contacts of a patient with meningococcal meningitis, the drug of choice is **Rifampicin** (alternatives: Ciprofloxacin or Ceftriaxone). * **Steroid Adjunct:** Dexamethasone should be administered **before or with the first dose of antibiotics** to reduce neurological complications (especially in *H. influenzae* and *S. pneumoniae*). * **Waterhouse-Friderichsen Syndrome:** A dreaded complication of meningococcemia involving adrenal hemorrhage and shock.

Q: What is the most common disease caused by CMV in post-renal transplant patients?

Pneumonia. **Explanation:** Cytomegalovirus (CMV) is the most significant viral pathogen in the post-transplant period, typically manifesting between 1 to 6 months after transplantation [1]. In the context of **renal transplant recipients**, while CMV can affect multiple organ systems, **Pneumonia (Interstitial Pneumonitis)** is considered the most common and serious tissue-invasive manifestation. It presents with fever, dry cough, and dyspnea, often showing bilateral interstitial infiltrates on chest X-ray. **Analysis of Options:** * **Option A (Pyelonephritis):** This is usually caused by bacterial pathogens (like *E. coli*) or Polyomavirus (BK virus) which causes nephropathy, but it is not a classic manifestation of CMV. * **Option B (Meningitis):** CMV rarely involves the CNS in transplant patients. CNS involvement is more common in HIV patients (as encephalitis) rather than transplant recipients. * **Option D (Gastrointestinal ulceration):** While CMV is a common cause of GI ulcers and colitis in immunocompromised states, in the specific hierarchy of post-renal transplant complications, pulmonary involvement (Pneumonia) takes precedence as the most common invasive disease. **High-Yield Pearls for NEET-PG:** * **Risk Factor:** The highest risk for CMV disease is in **Seronegative recipients receiving an organ from a Seropositive donor (D+/R-)** [2]. * **Diagnosis:** **pp65 antigenemia** assay or **Quantitative PCR** for CMV DNA are the preferred diagnostic methods [1]. * **Histology:** Look for **"Owl’s Eye" appearance** (large intranuclear inclusion bodies with a clear halo). * **Treatment:** **Valganciclovir** is used for prophylaxis, while **IV Ganciclovir** is the drug of choice for established CMV disease [2]. Foscarnet is used in ganciclovir-resistant cases.

Q: A 27-year-old man develops bilateral parotid gland swelling and orchitis, and is generally ill with fever of 102°F. Which of the following substances is most likely to be significantly elevated in the patient's serum?

Amylase. ### Explanation The clinical presentation of bilateral parotid swelling, fever, and orchitis in a young male is classic for **Mumps**, a viral infection caused by the *Rubulavirus* (Paramyxoviridae family). **Why Amylase is the Correct Answer:** Serum amylase is significantly elevated in mumps due to involvement of the **salivary glands** (parotitis). While amylase is commonly associated with the pancreas, it is also produced by the salivary glands (S-type isoenzyme). In mumps, inflammation and damage to the parotid acinar cells lead to the leakage of amylase into the bloodstream. Additionally, if the patient develops **mumps pancreatitis** (a known complication), the pancreatic isoenzyme (P-type) will also contribute to the elevation. **Why Other Options are Incorrect:** * **ALT and AST (Options A & C):** These are markers of hepatocellular injury. While some viral infections cause hepatitis, mumps typically spares the liver. Therefore, transaminases remain within normal limits. * **Ceruloplasmin (Option D):** This is a copper-binding protein and an acute-phase reactant. While it might rise slightly during general inflammation, it is not a specific or significant marker for mumps. It is primarily used in the diagnosis of Wilson’s disease. **NEET-PG High-Yield Pearls:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Unilateral Orchitis (can lead to testicular atrophy, but rarely causes infertility). * **Most common cause of sensorineural hearing loss in children:** Mumps (typically unilateral and permanent). * **Diagnosis:** Primarily clinical; confirmed by IgM antibodies or PCR from oral swabs/urine. * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain is most common).

Question 1

A 65-year-old woman undergoes a kidney transplant for CKD. Six weeks after the transplant, she develops CMV infection characterized by fever, malaise, and myalgias. Which of the following is a potential sequela of CMV infection?

Accepted Answer

GI ulcers and hemorrhage

Answer

Intra-abdominal abscess

Answer

Pyelonephritis

Answer

Cholecystitis

Question 2

A 37-year-old female presents to the emergency room with a fever. Chest x-ray shows multiple patchy infiltrates in both lungs. Echocardiography and blood cultures suggest a diagnosis of acute bacterial endocarditis limited to the tricuspid valve. Which of the following is the most probable etiology?

Accepted Answer

Illicit drug use

Answer

Congenital heart disease

Answer

Rheumatic fever

Answer

Rheumatoid arthritis

Question 3

What is true about miliary tuberculosis?

Accepted Answer

Commonly affects liver, kidney and spleen

Answer

Occurs following primary reactivation

Answer

Occurs following secondary reactivation

Answer

Both primary and secondary reactivation

Question 4

Clinical features of anicteric Leptospirosis are all EXCEPT:

Accepted Answer

High mortality

Answer

Influenza-like illness (fever, nausea, headache, hepatosplenomegaly)

Answer

Muscle pain

Answer

Conjunctival suffusion is the most common finding on physical examination

Question 5

A 6-year-old child presents with perianal pruritus, skin excoriation, and nocturnal enuresis, and is found to be infected with a parasite capable of autoinfection. What is the infective form of this parasite for humans?

Accepted Answer

Embryonated egg

Answer

Filariform larvae

Answer

Adult female

Answer

Adult male

Question 6

A laboratory technician was accidentally exposed to an HIV-seropositive serum sample. What is the role of zidovudine in the post-exposure prophylaxis for this patient?

Accepted Answer

To prevent acquisition of HIV infection.

Answer

To make the patient seronegative.

Answer

To delay the progression of the disease.

Answer

None of the above.

Question 7

A patient presents with high-grade fever and altered sensorium, and is diagnosed with meningococcal meningitis. Which of the following is the most appropriate empirical treatment?

Accepted Answer

Ceftriaxone

Answer

Piperacillin-Tazobactam

Answer

Penicillin

Answer

Cotrimoxazole

Question 8

What is the standard treatment for a patient with recently diagnosed sputum-positive pulmonary tuberculosis?

Accepted Answer

Rifampicin + Isoniazid + Pyrazinamide + Ethambutol

Answer

Rifampicin + Isoniazid + Pyrazinamide

Answer

Rifampicin + Isoniazid + Pyrazinamide + Streptomycin

Answer

Rifampicin + Isoniazid + Ethambutol

Question 9

What is the most common disease caused by CMV in post-renal transplant patients?

Accepted Answer

Pneumonia

Answer

Pyelonephritis

Answer

Meningitis

Answer

Gastrointestinal ulceration

Question 10

A 27-year-old man develops bilateral parotid gland swelling and orchitis, and is generally ill with fever of 102°F. Which of the following substances is most likely to be significantly elevated in the patient's serum?

Accepted Answer

Amylase

Answer

Alanine aminotransferase (ALT)

Answer

Aspartate aminotransferase (AST)

Answer

Ceruloplasmin

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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