Infectious Diseases Practice Questions

Q: Which of the following is not related to kala azar?

Tropical splenomegaly syndrome. The correct answer is **D. Tropical splenomegaly syndrome**, as it is a distinct clinical entity unrelated to Visceral Leishmaniasis (Kala-azar). **1. Why Tropical Splenomegaly Syndrome (TSS) is the correct answer:** TSS, also known as **Hyper-reactive Malarial Splenomegaly (HMS)**, is an abnormal immunological response to chronic or repeated **Malaria** infections (usually *P. falciparum*). It is characterized by massive splenomegaly, high titers of anti-malarial antibodies, and elevated serum IgM. It is not caused by *Leishmania donovani*. **2. Analysis of incorrect options (Features of Kala-azar):** * **Pancytopenia:** Kala-azar causes bone marrow suppression and splenic sequestration, leading to anemia, leucopenia, and thrombocytopenia. [2] * **Oral Miltefosine:** This is the first effective **oral** treatment for Visceral Leishmaniasis. It is highly effective but contraindicated in pregnancy due to teratogenicity. * **Hyperpigmentation:** The name "Kala-azar" literally translates to "Black Fever." It refers to the characteristic dusky hyperpigmentation of the skin (especially on the forehead, hands, and abdomen) seen in Indian patients. **Clinical Pearls for NEET-PG:** * **Vector:** Sandfly (*Phlebotomus argentipes*). [1] * **Gold Standard Diagnosis:** Demonstration of **LD bodies** (Amastigotes) in splenic aspirate (highest sensitivity) or bone marrow biopsy. [2] * **Drug of Choice:** **Liposomal Amphotericin B** is currently the preferred treatment due to high cure rates and low resistance. * **PKDL:** Post-Kala-azar Dermal Leishmaniasis occurs in 5-10% of cases in India after the apparent cure of systemic disease, acting as a reservoir for infection.

Q: Mucosal invasion of the intestine causes which type of diarrhea?

Dysentery. **Explanation:** The correct answer is **Dysentery**. **1. Understanding the Mechanism (Why Dysentery is correct):** Diarrhea is broadly classified into secretory (watery) and inflammatory (invasive). When pathogens (such as *Shigella*, *Entamoeba histolytica*, or Enteroinvasive *E. coli*) invade the intestinal mucosa, they cause direct cellular damage, inflammation, and ulceration [1]. This process results in the release of blood, mucus, and inflammatory cells (pus) into the intestinal lumen. This clinical presentation—small-volume stools containing blood and mucus, often accompanied by tenesmus (straining) and fever—is defined as **dysentery** [1]. **2. Analysis of Incorrect Options:** * **Watery diarrhea (Option A):** This is typically caused by non-invasive pathogens (e.g., *Vibrio cholerae*, ETEC) or viruses (e.g., Rotavirus) [1]. These organisms produce toxins that alter electrolyte transport (secretory) or cause osmotic imbalances without destroying the mucosal architecture. * **Rice stool (Option B):** This is a specific subtype of profound watery diarrhea characteristic of **Cholera**. It is caused by the *Cholera toxin* acting on adenylate cyclase, leading to massive secretion of water and electrolytes without mucosal invasion [3]. **3. NEET-PG Clinical Pearls:** * **Site of Involvement:** Invasive diarrhea (Dysentery) usually involves the **large intestine (colon)**, whereas watery diarrhea usually involves the **small intestine**. * **Common Pathogens:** * *Bacillary Dysentery:* Most common cause is **Shigella** (specifically *S. sonnei* in developed and *S. dysenteriae* in developing regions). * *Amoebic Dysentery:* Caused by **Entamoeba histolytica** (look for "flask-shaped ulcers" on biopsy) [2]. * **Key Distinction:** Fever is a hallmark of invasive/inflammatory diarrhea but is usually absent or low-grade in pure secretory diarrhea.

Q: Rabies encephalitis presents with all of the following clinical features except?

Hypotonic paralysis. **Explanation:** Rabies is a fatal viral encephalitis caused by the Lyssavirus (Rhabdoviridae family). The clinical presentation typically follows two patterns: **Encephalitic (Furious) Rabies** (80%) and **Paralytic (Dumb) Rabies** (20%). **Why Option D is the Correct Answer:** In the classic **Encephalitic (Furious) Rabies** described in the question, the hallmark is **hyper-excitability** and **spasticity**, not hypotonia. While Paralytic Rabies exists, it presents as an ascending symmetrical paralysis (resembling Guillain-Barré Syndrome). However, in the context of "Rabies Encephalitis" symptoms like spasms and phobias, **Hypotonic paralysis** is the "except" because the disease is characterized by intense muscle spasms and autonomic hyperactivity. **Analysis of Incorrect Options:** * **A. Tonic spasm of body:** Irritation of the motor neurons leads to generalized tonic-clonic spasms, often triggered by sensory stimuli (light, sound, or touch). * **B. Sound phobia:** Patients experience extreme "sensory hyperesthesia." Loud noises (Aerophobia/Akoustophobia) can trigger violent spasms of the diaphragm and accessory respiratory muscles. * **C. Hypersalivation:** Rabies causes autonomic dysfunction and excessive lacrimation/salivation. Combined with **hydrophobia** (spasms of deglutition muscles when seeing water), this leads to the classic "foaming at the mouth." **NEET-PG High-Yield Pearls:** * **Pathognomonic Sign:** **Negri Bodies** (intracytoplasmic eosinophilic inclusions) found most commonly in **Hippocampus** (Pyramidal cells) and **Cerebellum** (Purkinje cells). * **Mechanism:** The virus binds to **Nicotinic Acetylcholine Receptors** at the neuromuscular junction. * **Incubation Period:** Usually 1–3 months; depends on the distance of the bite from the CNS. * **Prophylaxis:** Category III bites (transdermal) require both **Rabies Vaccine** and **Rabies Immunoglobulin (RIG)**.

Q: A patient diagnosed with influenza reported onset of symptoms 18 hours ago. Which of the following is the most appropriate treatment for this patient?

Oseltamivir. ### **Explanation** **Correct Answer: C. Oseltamivir** **Mechanism & Rationale:** Oseltamivir is a **Neuraminidase Inhibitor** effective against both Influenza A and B. Neuraminidase is an enzyme essential for the release of newly formed virions from infected host cells; by inhibiting it, the drug prevents the spread of the virus within the respiratory tract. The clinical efficacy of neuraminidase inhibitors is highly time-dependent. They are most effective when initiated within **48 hours** of symptom onset. Since this patient presented at 18 hours, Oseltamivir is the treatment of choice to reduce the duration and severity of symptoms. **Analysis of Incorrect Options:** * **A. Amantadine:** This is an M2 ion channel blocker that prevents viral uncoating. It is only active against Influenza A. However, it is no longer recommended for routine use due to widespread high-level resistance (nearly 100%) among circulating strains. * **B. Foscarnet:** This is a pyrophosphate analog used primarily for CMV retinitis or acyclovir-resistant HSV/VZV infections. It has no role in treating influenza. * **C. Ribavirin:** While it has broad-spectrum antiviral activity, it is primarily used for Chronic Hepatitis C (in combination) and severe RSV infections. It is not a first-line treatment for influenza. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Administration:** Oseltamivir is oral; **Zanamivir** is inhaled (contraindicated in asthma/COPD); **Peramivir** is intravenous. * **Baloxavir Marboxil:** A newer single-dose drug that inhibits the "cap-snatching" endonuclease activity of the viral RNA polymerase. * **Chemoprophylaxis:** Oseltamivir can be used for post-exposure prophylaxis in high-risk individuals. * **Antigenic Drift vs. Shift:** Drift (point mutations) causes seasonal epidemics; Shift (reassortment) causes pandemics.

Q: A 45-year-old female is diagnosed as a case of pneumococcal meningitis. Her blood samples were sent for culture sensitivity. In the meantime, what is the best empirical treatment?

Vancomycin + ceftriaxone. **Explanation:** The management of bacterial meningitis is a medical emergency requiring immediate empirical antibiotic therapy before culture results are available [1]. **1. Why Vancomycin + Ceftriaxone is correct:** * **Ceftriaxone (3rd Gen Cephalosporin):** This is the backbone of empirical therapy due to its excellent CSF penetration and broad-spectrum activity against common pathogens like *S. pneumoniae* and *N. meningitidis* [1]. * **Vancomycin:** Due to the rising global prevalence of **Penicillin-resistant *Streptococcus pneumoniae* (PRSP)** and increasing resistance to cephalosporins, Vancomycin is added empirically [3]. This ensures coverage against highly resistant strains until sensitivities are confirmed. * **Synergy:** The combination provides the most reliable bactericidal activity against the most likely causative organisms in an adult. **2. Why other options are incorrect:** * **Penicillin G:** While historically the drug of choice, it is no longer used empirically due to widespread resistance in *S. pneumoniae*. It is only used if the isolate is proven to be highly sensitive [3]. * **Doxycycline:** This is a bacteriostatic drug with poor CSF penetration; it is not indicated for acute bacterial meningitis. * **Streptomycin:** An aminoglycoside that has poor CNS penetration and is primarily used for Tuberculosis or specific infections like Plague/Tularemia, not for acute pneumococcal meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **Dexamethasone:** Should be administered **20 minutes before or with the first dose** of antibiotics to reduce neurological complications (hearing loss/edema) in pneumococcal meningitis [2]. * **Listeria Coverage:** If the patient is >50 years old or immunocompromised, **Ampicillin** must be added to the Vancomycin + Ceftriaxone regimen. * **Drug of Choice (DOC):** Once sensitivity is known, if the strain is penicillin-susceptible, Penicillin G becomes the DOC.

Question 1

Which of the following hepatitis infections has the worst prognosis?

Accepted Answer

Hepatitis D Virus (HDV) Superinfection on Hepatitis B Virus (HBV) Infection

Answer

Hepatitis B Virus (HBV) Infection

Answer

Hepatitis D Virus (HDV) Infection

Answer

Hepatitis B Virus (HBV) and Hepatitis D Virus (HDV) Coinfection

Question 2

A 44-year-old man with a prior renal transplant presents with cough and shortness of breath on exertion. He denies sputum production and has no prior respiratory or cardiac illnesses. On physical examination, he appears dyspneic, respirations 24/min, pulse 110/min, and oxygen saturation 88%. His lungs are clear on auscultation and heart sounds are normal. Chest X-ray shows bilateral diffuse perihilar infiltrates. Bronchoscopy and bronchial brushings show clusters of cysts that stain with methenamine silver. Which of the following is the most appropriate next step in management?

Accepted Answer

trimethoprim-sulfamethoxazole

Answer

amphotericin B

Answer

cephalosporins

Answer

aminoglycosides

Question 3

Which of the following is not related to kala azar?

Accepted Answer

Tropical splenomegaly syndrome

Answer

Pancytopenia

Answer

Oral miltefosine

Answer

Hyperpigmentation

Question 4

Mucosal invasion of the intestine causes which type of diarrhea?

Accepted Answer

Dysentery

Answer

Watery diarrhea

Answer

Rice stool

Answer

None

Question 5

In a patient with cerebral malaria, which of the following asexual stages of Plasmodium falciparum can be seen on peripheral smear?

Accepted Answer

Tropozoites

Answer

Schizonts

Answer

Gametocytes

Answer

Hypnozoites

Question 6

What are the major signs included by WHO for AIDS diagnosis?

Accepted Answer

Chronic diarrhea > 1 month

Answer

Chronic cough > 1 month

Answer

Chronic fever > 1 month

Answer

Weight loss of at least 10% of body weight

Question 7

Rabies encephalitis presents with all of the following clinical features except?

Accepted Answer

Hypotonic paralysis

Answer

Tonic spasm of body

Answer

Sound phobia

Answer

Hypersalivation

Question 8

A patient diagnosed with influenza reported onset of symptoms 18 hours ago. Which of the following is the most appropriate treatment for this patient?

Accepted Answer

Oseltamivir

Answer

Amantadine

Answer

Foscarnet

Answer

Ribavirin

Question 9

A 45-year-old female is diagnosed as a case of pneumococcal meningitis. Her blood samples were sent for culture sensitivity. In the meantime, what is the best empirical treatment?

Accepted Answer

Vancomycin + ceftriaxone

Answer

Penicillin G

Answer

Doxycycline

Answer

Streptomycin

Question 10

A 30-year-old person presents with fever and headache for 20 days. CSF values are: glucose 38 mg/dL, protein 60 mg/dL, and lymphocyte pleocytosis with 20 cells/mm³. What should be included in the initial investigations?

Accepted Answer

Herpes Simplex Virus (HSV) detection

Answer

Indian ink smear of CSF

Answer

Acid-Fast Bacilli (AFB) stain

Answer

Toxoplasmosis testing

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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