Infectious Diseases Practice Questions

Q: What is the drug of choice for cytomegalovirus retinitis in HIV patients?

Ganciclovir. **Explanation:** **Cytomegalovirus (CMV) Retinitis** is the most common opportunistic ocular infection in HIV patients, typically occurring when the CD4 count falls below **50 cells/mm³**. It is characterized by "pizza-pie" or "cheese and ketchup" fundoscopic appearances (hemorrhage with yellowish-white exudates). **Why Ganciclovir is the Correct Answer:** Ganciclovir is a nucleoside analogue that inhibits viral DNA polymerase [1]. It is the **drug of choice** for CMV retinitis because it has high efficacy against CMV compared to other antivirals as it allows preferential phosphorylation by protein kinases of cytomegalovirus [1]. It can be administered intravenously, orally (Valganciclovir), or via intravitreal implants [1]. Valganciclovir (the prodrug) is now often preferred for induction and maintenance therapy due to its excellent oral bioavailability. **Why Other Options are Incorrect:** * **Acyclovir:** Primarily used for Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV) [1]. It lacks significant activity against CMV because CMV does not produce the enzyme *thymidine kinase* required to activate Acyclovir [1]. * **Ribavirin:** Used mainly for Hepatitis C (in combination) and Respiratory Syncytial Virus (RSV). It is not effective against CMV. * **Vidarabine:** An older antiviral previously used for HSV keratitis; it is rarely used today due to systemic toxicity and the availability of superior agents like Ganciclovir. **High-Yield Clinical Pearls for NEET-PG:** 1. **Side Effects:** The major dose-limiting side effect of Ganciclovir is **bone marrow suppression** (neutropenia and thrombocytopenia). 2. **Alternative Drugs:** If Ganciclovir resistance occurs (UL97 mutation), **Foscarnet** or **Cidofovir** are used. Note that Foscarnet is highly nephrotoxic. 3. **Prevention:** The best long-term prevention for CMV retinitis is the restoration of the immune system via **Highly Active Antiretroviral Therapy (HAART)**.

Q: Which of the following conditions is characterized by a double rise of temperature within a 24-hour period?

Kala Azar. The correct answer is **Kala Azar (Visceral Leishmaniasis)**. **Why Kala Azar is correct:** Kala Azar is classically associated with a **"double peak" of fever** (bimodal fever) within a single 24-hour period [1]. This occurs due to the rapid multiplication of *Leishmania donovani* within the reticuloendothelial system. While not present in every case, it is a highly characteristic clinical sign often tested in exams. **Analysis of Incorrect Options:** * **Malaria:** Characterized by periodic paroxysms (chills, fever, and sweating). Depending on the species, the fever occurs every 48 hours (*P. vivax/falciparum* - Tertian) or 72 hours (*P. malariae* - Quartan), but not twice daily. * **Tuberculosis:** Typically presents with an **evening rise of temperature** (low-grade fever) accompanied by night sweats [1]. * **Hodgkin’s Lymphoma:** Classically associated with **Pel-Ebstein fever**, where bouts of high fever alternate with afebrile periods lasting days to weeks [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Kala Azar Triad:** Massive splenomegaly (often crossing the midline), hepatomegaly, and pancytopenia [1]. * **Skin Changes:** The name "Kala Azar" (Black Fever) comes from the hyperpigmentation of the skin (especially on the forehead and hands) seen in Indian patients. * **Diagnosis:** The gold standard is a splenic aspirate (highest yield), but bone marrow aspiration is safer [1]. Look for **LD bodies** (Amastigote form) in macrophages. * **Drug of Choice:** Liposomal Amphotericin B is currently the preferred treatment.

Q: Kala azar is which of the following types of leishmaniasis?

Visceral leishmaniasis. **Explanation:** **Kala-azar**, also known as "Black Fever," is the most severe form of leishmaniasis caused by the protozoan parasite *Leishmania donovani* complex (primarily *L. donovani* and *L. infantum*) [1]. It is classified as **Visceral Leishmaniasis (Option D)** because the parasites migrate to the internal (visceral) organs, specifically the reticuloendothelial system, including the liver, spleen, and bone marrow [1]. **Analysis of Options:** * **Visceral Leishmaniasis (Correct):** Characterized by systemic involvement. The hallmark clinical triad includes prolonged irregular fever, massive splenomegaly (often "huge" or "dragging" sensation), and significant weight loss/anemia [1]. * **Cutaneous Leishmaniasis (B):** This form is limited to the skin, causing ulcers at the site of the sandfly bite [2]. It is typically caused by *L. tropica* or *L. major*. * **Oriental Sore (C):** This is simply a synonym for Old World Cutaneous Leishmaniasis [2]. * **Mucocutaneous Leishmaniasis (A):** Primarily seen in the New World (caused by *L. braziliensis*), this form involves the destruction of the mucous membranes of the nose, mouth, and throat [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Transmitted by the bite of the female **Phlebotomus sandfly** [1]. * **Infective Stage:** Promastigote; **Diagnostic Stage:** Amastigote (LD bodies) [1]. * **Gold Standard Diagnosis:** Bone marrow or splenic aspirate showing **LD bodies** (Amastigotes in macrophages) [1]. * **Drug of Choice:** **Liposomal Amphotericin B** is currently the preferred treatment. * **Post-Kala-azar Dermal Leishmaniasis (PKDL):** A sequel where skin lesions appear after the apparent cure of visceral leishmaniasis; it acts as an important reservoir for the disease [2].

Q: Kernig's sign is seen in which of the following conditions?

Acute bacterial meningitis. **Explanation:** **Kernig’s sign** is a classic clinical indicator of **meningeal irritation** [1]. It is elicited with the patient lying supine; the hip and knee are flexed to 90 degrees, and the examiner then attempts to passively extend the knee. The sign is positive if there is resistance or pain in the lower back/posterior thigh, preventing full extension [1]. This occurs because the maneuver stretches the inflamed spinal nerve roots and hypersensitive meninges. * **Acute Bacterial Meningitis (Correct):** This condition involves inflammation of the leptomeninges (arachnoid and pia mater) [1]. The resulting meningismus leads to protective spinal muscle spasms, making Kernig’s sign a hallmark physical finding, alongside Brudzinski’s sign and nuchal rigidity [1]. * **Pneumonia:** This is a localized infection of the lung parenchyma. While severe pneumonia can cause systemic illness, it does not involve the meninges and therefore does not produce Kernig’s sign. * **Mental Retardation & Cerebral Palsy:** These are neurodevelopmental/static encephalopathic conditions. While cerebral palsy may present with spasticity, it lacks the acute inflammatory process of the meninges required to trigger a positive Kernig’s sign. **Clinical Pearls for NEET-PG:** * **Brudzinski’s Sign:** Passive flexion of the neck leads to involuntary flexion of the hips and knees [1]. * **Sensitivity vs. Specificity:** Both Kernig’s and Brudzinski’s signs have **low sensitivity** (often absent in elderly or infants) but **high specificity** for meningitis. * **Jolt Accentuation Maneuver:** Asking the patient to turn their head horizontally 2-3 times per second; worsening of headache is the most sensitive clinical sign for meningitis.

Q: A patient presents with acute onset high-grade fever, chills, productive cough with rusty-colored sputum, and pleuritic chest pain. The chest X-ray is shown below. What is the most likely diagnosis?

Pneumococcal Pneumonia. ***Pneumococcal Pneumonia*** - **Lobar consolidation** on chest X-ray is the classic radiographic pattern for **Streptococcus pneumoniae** pneumonia. - Most common cause of **community-acquired pneumonia** in immunocompetent adults, presenting with homogeneous consolidation affecting an entire lobe. *Tuberculosis* - Typically presents with **upper lobe involvement** and **cavitation** on chest imaging, not lobar consolidation. - Associated with **night sweats**, **weight loss**, and **chronic cough** over weeks to months. *Klebsiella pneumonia* - Usually causes **upper lobe consolidation** with **bulging fissure sign** and potential **cavitation**. - More commonly seen in **alcoholics** and **diabetics**, with thick, bloody sputum production. *Pneumocystis pneumonia* - Characterized by **bilateral interstitial infiltrates** or **ground-glass opacities**, not lobar consolidation. - Occurs almost exclusively in **immunocompromised patients** (HIV, organ transplant recipients).

Q: The oral lesion called mucous patches is usually multiple, grayish white plaques associated with what?

No pain. **Explanation:** The correct answer is **B. No pain**. **Mucous patches** are a classic clinical manifestation of **Secondary Syphilis**, caused by the spirochete *Treponema pallidum*. These lesions are highly infectious, slightly elevated, grayish-white, or "snail-track" erosions that appear on the oral mucosa, tongue, or tonsils [1]. A hallmark feature of syphilitic lesions (both the primary chancre and secondary mucous patches) is that they are characteristically **painless** [1]. This lack of pain is a crucial diagnostic differentiator from other ulcerative oral conditions. **Analysis of Incorrect Options:** * **A. Pain:** Unlike aphthous ulcers or herpetic stomatitis, which are exquisitely painful [2], syphilitic mucous patches do not cause significant discomfort. * **C. Itching:** Pruritus (itching) is rarely a feature of mucosal syphilis. While the secondary syphilis skin rash (maculopapular) is famously non-itchy [1], the mucosal lesions are also asymptomatic. * **D. Burning sensation:** This is typically associated with conditions like oral candidiasis (thrush) or lichen planus, rather than syphilis. **High-Yield Clinical Pearls for NEET-PG:** * **Secondary Syphilis** is known as the "Great Imitator." It typically presents with a generalized maculopapular rash (including palms and soles), generalized lymphadenopathy, and mucous patches [1]. * **Condyloma Lata:** These are moist, wart-like, painless papules found in intertriginous areas (like the anogenital region), also characteristic of secondary syphilis [1]. * **Diagnosis:** Screening is done via non-specific treponemal tests (**VDRL/RPR**), and confirmation is via specific tests (**FTA-ABS/TPHA**). * **Treatment:** The drug of choice for all stages of syphilis remains **Benzathine Penicillin G**.

Q: Which of the following pneumonias is caused by contaminated air conditioners?

Legionella. **Explanation:** **Legionella pneumophila** is the correct answer because it is an aerobic, Gram-negative rod that thrives in aquatic environments. It colonizes man-made water systems such as **air conditioning cooling towers**, humidifiers, whirlpool spas, and showerheads [1]. Transmission occurs via the **inhalation of contaminated aerosols** (mists) produced by these systems. It does not spread person-to-person . **Analysis of Incorrect Options:** * **A. Pneumococci (*S. pneumoniae*):** The most common cause of community-acquired pneumonia (CAP). It is part of the normal nasopharyngeal flora and spreads via respiratory droplets, not environmental water systems. * **B. Staphylococci (*S. aureus*):** Typically causes post-viral pneumonia (e.g., after Influenza) or hematogenous spread (e.g., IV drug users) [1]. It is associated with skin flora and hospital environments. * **C. E. coli:** An enteric Gram-negative organism. It primarily causes pneumonia in neonates or via aspiration in debilitated/ICU patients; it is not associated with aerosolized water from AC units. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Look for "atypical pneumonia" features—high fever, **diarrhea** (GI symptoms), and **hyponatremia** (low sodium). * **Diagnosis:** The **Urinary Antigen Test** is the rapid test of choice. Culture requires **Buffered Charcoal Yeast Extract (BCYE) agar** supplemented with L-cysteine and iron. * **Treatment:** Macrolides (Azithromycin) or Fluoroquinolones (Levofloxacin). It is inherently resistant to Beta-lactams because it is an intracellular pathogen. * **Pontiac Fever:** A milder, flu-like illness caused by *Legionella* without pneumonia.

Q: Mulberry molars are characteristic features of which condition?

Congenital syphilis. **Explanation:** **Congenital Syphilis (Correct Answer):** Mulberry molars are a pathognomonic dental abnormality caused by the transplacental transmission of *Treponema pallidum*. The infection leads to inflammation of the tooth germ during the morphodifferentiation stage of development. This results in the permanent first molars having multiple, poorly developed rudimentary cusps and a narrowed occlusal surface, giving them a bumpy, "mulberry-like" appearance. **Analysis of Incorrect Options:** * **Severe Fluorosis:** Characterized by "mottling" of enamel, presenting as chalky white patches or brownish discoloration and pitting, but it does not produce the specific multi-cusped morphology of mulberry molars. * **Trauma at birth:** While trauma can cause localized enamel hypoplasia (Turner’s tooth), it typically affects a single tooth and does not result in the symmetrical, multi-cusped pattern seen in syphilis. * **Chronic suppurative abscess:** Localized infection (Turner’s hypoplasia) usually affects the permanent successor of a primary tooth (like a premolar) due to apical periodontitis of the deciduous tooth, rather than systemic developmental changes. **NEET-PG High-Yield Pearls:** * **Hutchinson’s Triad:** A classic triad of Congenital Syphilis consisting of: 1. **Hutchinson’s teeth:** Notched, peg-shaped permanent incisors. 2. **Interstitial keratitis:** Leading to corneal scarring. 3. **Sensorineural hearing loss:** Due to 8th cranial nerve involvement. * **Other Skeletal Signs:** Saddle nose deformity, Saber shins (anterior bowing of the tibia), and Clutton’s joints (painless symmetrical knee swelling). * **Early vs. Late:** Mulberry molars are considered a "stigmata" or late manifestation (appearing after age 2).

Question 1

What is the drug of choice for cytomegalovirus retinitis in HIV patients?

Accepted Answer

Ganciclovir

Answer

Acyclovir

Answer

Ribavarin

Answer

Vidarabine

Question 2

Which of the following conditions is characterized by a double rise of temperature within a 24-hour period?

Accepted Answer

Kala Azar

Answer

Malaria

Answer

Tuberculosis

Answer

Hodgkin's lymphoma

Question 3

Kala azar is which of the following types of leishmaniasis?

Accepted Answer

Visceral leishmaniasis

Answer

Mucocutaneous leishmaniasis

Answer

Cutaneous leishmaniasis

Answer

Oriental sore

Question 4

Seizures may be the presenting feature in all of the following, except?

Accepted Answer

Entamoeba histolytica

Answer

Cryptococcus meningitis

Answer

Toxoplasmosis

Answer

CMV

Question 5

Kernig's sign is seen in which of the following conditions?

Accepted Answer

Acute bacterial meningitis

Answer

Pneumonia

Answer

Mental retardation

Answer

Cerebral palsy

Question 6

A patient presents with acute onset high-grade fever, chills, productive cough with rusty-colored sputum, and pleuritic chest pain. The chest X-ray is shown below. What is the most likely diagnosis?

Accepted Answer

Pneumococcal Pneumonia

Answer

Tuberculosis

Answer

Klebsiella pneumonia

Answer

Pneumocystis pneumonia

Question 7

What represents a medical emergency in an asplenic patient?

Accepted Answer

Dog bite

Answer

Cat bite

Answer

Fish bite

Answer

Human bite

Question 8

The oral lesion called mucous patches is usually multiple, grayish white plaques associated with what?

Accepted Answer

No pain

Answer

Pain

Answer

Itching

Answer

Burning sensation

Question 9

Which of the following pneumonias is caused by contaminated air conditioners?

Accepted Answer

Legionella

Answer

Pneumococci

Answer

Staphylococci

Answer

E. coli

Question 10

Mulberry molars are characteristic features of which condition?

Accepted Answer

Congenital syphilis

Answer

Severe fluorosis

Answer

Trauma at the time of birth

Answer

Chronic suppurative abscess in overlying gingival tissue

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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