Infectious Diseases Practice Questions

Q: The Jarisch-Herxheimer reaction is typically seen during the treatment of which condition?

Syphilis. The **Jarisch-Herxheimer Reaction (JHR)** is an acute febrile response that occurs following the initiation of antimicrobial therapy for spirochetal infections, most classically **Syphilis** (*Treponema pallidum*). **Why Syphilis is correct:** The reaction is triggered by the rapid death of spirochetes, which leads to the release of bacterial endotoxins and lipoproteins (like pyrogen) into the bloodstream. This causes a systemic inflammatory response characterized by fever, chills, rigors, headache, myalgia, and exacerbation of skin lesions. It typically occurs within 2–24 hours of the first dose of Penicillin [1]. While it can occur in any stage of syphilis, it is most common in **Secondary Syphilis** (up to 70–90% of cases). **Why other options are incorrect:** * **Impetigo & Erysipelas:** These are superficial skin infections caused by *Staphylococcus aureus* or *Streptococcus pyogenes*. While treatment can cause mild side effects, they do not trigger the specific cytokine storm associated with JHR. * **Typhoid:** Caused by *Salmonella Typhi*, this presents with a

Q: What is the most common site for intestinal tuberculosis?

Distal ileum. **Explanation:** The **ileocecal region** (specifically the **distal ileum**) is the most common site for intestinal tuberculosis, accounting for approximately 75% of cases. **Why the Distal Ileum?** The preference for this site is due to three primary physiological factors: 1. **Increased Lymphoid Tissue:** The distal ileum contains a high density of **Peyer’s patches**. *Mycobacterium tuberculosis* is an intracellular pathogen that is phagocytosed by macrophages and transported into these lymphoid follicles. 2. **Physiological Stasis:** The presence of the ileocecal valve leads to prolonged contact time between the infected contents (ingested sputum or contaminated milk) and the intestinal mucosa. 3. **Increased Absorption:** This region has a high rate of fluid and electrolyte absorption, which facilitates the entry of the bacilli into the intestinal wall. **Analysis of Incorrect Options:** * **B. Jejunum:** While tuberculosis can affect any part of the GI tract, the jejunum has fewer Peyer’s patches and faster transit times, making it a less common site. * **C. Sigmoid colon:** Isolated colonic TB is rare; when it occurs, it usually involves the proximal colon. * **D. Ascending colon:** Though the cecum (adjacent to the ascending colon) is frequently involved as part of "ileocecal TB," the distal ileum remains the primary focus of lymphoid involvement. **Clinical Pearls for NEET-PG:** * **Morphological Types:** The **ulcerative** form is most common (seen in secondary TB), while the **hyperplastic** form (seen in primary TB) can mimic Crohn’s disease or malignancy. * **Ulcers:** TB ulcers are typically **transverse** (circumferential), unlike the longitudinal ulcers seen in Crohn’s disease. * **Complications:** Stricture formation is the most common complication, leading to intestinal obstruction. * **Gold Standard Diagnosis:** Colonoscopy with biopsy showing **caseating granulomas**.

Q: A client is prescribed with Pentamidine IV for the treatment of Pneumocystis jirovecii pneumonia. Suddenly, the client develops a temperature of 101.5°F. Which of the following would this sign most likely indicate?

The client has developed another infection.. Explanation:1. Why Option C is Correct:*Pneumocystis jirovecii* pneumonia (PJP) is an opportunistic infection primarily seen in immunocompromised patients (e.g., HIV/AIDS with CD4 <200). Pentamidine is a potent antiprotozoal agent [1] used when first-line Trimethoprim-Sulfamethoxazole (TMP-SMX) is contraindicated. A sudden spike in temperature (101.5°F) during treatment is a clinical "red flag." In an immunocompromised host, a new fever often signifies a **secondary opportunistic infection** (bacterial, viral, or fungal) or a "superinfection" rather than a reaction to the drug itself. Pentamidine is more commonly associated with hypotension and hypoglycemia rather than drug-induced pyrexia.2. Why Other Options are Incorrect:* **Option A:** Pentamidine overdose typically manifests as severe hypotension, cardiac arrhythmias (QT prolongation), or acute renal failure, not isolated fever.* **Option B:** Fever is a sign of clinical change, not a marker of sub-therapeutic dosing. Increasing the dose without investigation could lead to severe toxicity.* **Option D:** Therapeutic effect in PJP is indicated by improved oxygenation (PaO2), decreased respiratory rate, and resolution of fever, not the onset of a new high-grade fever.3. NEET-PG High-Yield Pearls:* **Drug of Choice for PJP:** TMP-SMX (Prophylaxis and Treatment).* **Pentamidine Side Effects:** "The 3 Hypos" — **Hypo**tension (especially with rapid IV infusion), **Hypo**glycemia (due to pancreatic islet cell toxicity), and **Hypo**calcemia. It can also cause Nephrotoxicity and Pancreatitis.* **Clinical Tip:** Always monitor Blood Glucose and Blood Pressure in patients on Pentamidine.* **Alternative for PJP:** Atovaquone or Clindamycin + Primaquine.

Q: Which of the following statements is FALSE regarding Infectious mononucleosis?

Non-suppurative, painless lymphadenopathy. **Explanation:** Infectious Mononucleosis (IM), primarily caused by the **Epstein-Barr Virus (EBV)**, is characterized by the classic triad of fever, pharyngitis, and lymphadenopathy. **1. Why Option A is the correct (False) statement:** While the lymphadenopathy in IM is indeed non-suppurative and typically involves the posterior cervical chain, it is characteristically **tender (painful)** to palpation, especially during the acute phase. The statement "painless lymphadenopathy" is more suggestive of malignancies like lymphoma or chronic infections like tuberculosis, making this the false statement regarding IM. **2. Analysis of other options:** * **Option B:** A faint maculopapular or petechial rash can occur. Notably, a prominent pruritic maculopapular rash develops in ~90% of patients if they are mistakenly treated with **Ampicillin or Amoxicillin**. * **Option C:** A hallmark of IM is absolute lymphocytosis (>50% of total WBCs) with **>10% atypical lymphocytes** (Downey cells) [1]. These are actually activated T-cells (CD8+) reacting against the EBV-infected B-cells. * **Option D:** **Hoagland sign** refers to transient bilateral upper eyelid edema, which can be an early clinical clue appearing before the lymphadenopathy. **Clinical Pearls for NEET-PG:** * **Diagnosis:** Heterophile antibody test (**Monospot test**) is the screening test of choice. * **Complication:** Splenic rupture is a rare but life-threatening complication; patients should avoid contact sports for 3–4 weeks. * **Association:** EBV is linked to Burkitt lymphoma, Nasopharyngeal carcinoma, and Oral Hairy Leukoplakia in HIV patients [1].

Q: Which is the commonest complication of Mumps in adults?

Orchitis. **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). While it primarily presents as parotitis in children, the clinical profile changes significantly in post-pubertal adults. **Why Orchitis is the Correct Answer:** **Epididymo-orchitis** is the most common extra-salivary complication of mumps in post-pubertal males, occurring in approximately **20-30%** of cases. It is typically unilateral (70%) and characterized by high fever, severe testicular pain, and swelling. While it can lead to testicular atrophy in about 50% of affected patients, permanent sterility is rare because the involvement is usually unilateral. **Analysis of Incorrect Options:** * **A. Encephalitis:** While CNS involvement is common (CSF pleocytosis in 50%), clinical encephalitis is rare (<1%). Aseptic meningitis is more frequent than encephalitis but still less common than orchitis in adults. * **C. Pancreatitis:** Occurs in about 5% of cases. It usually presents as mild epigastric pain and is often transient. * **D. Carditis:** Myocarditis is a rare complication of mumps and is seldom clinically significant. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic Meningitis. * **Most common complication in adult females:** Oophoritis (approx. 5%). * **Deafness:** Mumps is a classic cause of sudden onset **unilateral** sensorineural hearing loss (SNHL). * **Diagnosis:** Primarily clinical; however, elevated **Serum Amylase** is a characteristic laboratory finding (due to both parotitis and pancreatitis). * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain is most common).

Q: Exposure to which of the following conditions necessitates passive immunization with standard immune serum globulin?

Hepatitis A. The core concept of this question lies in the distinction between **Standard Immune Serum Globulin (IG)** and **Hyperimmune (Specific) Globulins**. **1. Why Hepatitis A is correct:** Standard Immune Serum Globulin (IG) is prepared from large pools of plasma from the general population and contains antibodies against common prevalent diseases. **Hepatitis A** is the classic indication for standard IG [1]. It is used for post-exposure prophylaxis (PEP) in non-immune individuals (within 14 days of exposure) and for pre-exposure prophylaxis in travelers to endemic areas when the vaccine is contraindicated or there is insufficient time for the vaccine to work. **2. Why the other options are incorrect:** * **Rabies (A):** Requires **Human Rabies Immune Globulin (HRIG)**, which is a specific hyperimmune globulin with high titers of anti-rabies antibodies. * **Hepatitis B (C):** Requires **Hepatitis B Immune Globulin (HBIG)**, prepared from donors with high titers of anti-HBs. * **Tetanus (D):** Requires **Tetanus Immune Globulin (TIG)** for passive immunization in wound management. **3. NEET-PG Clinical Pearls:** * **Standard IG** is also used in the treatment of Measles (post-exposure) and as replacement therapy in primary immunodeficiency (e.g., Agammaglobulinemia). * **Hyperimmune Globulins** are preferred for Rabies, Tetanus, Hepatitis B, Varicella (VZIG), and CMV because they provide a concentrated, predictable dose of specific antibodies. * **Timing:** For Hepatitis A, passive immunization is most effective if given within **2 weeks** of exposure [1]. * **Route:** Most globulins are given Intramuscularly (IM), though IVIG is used for systemic inflammatory or immunodeficiency states.

Q: A 32-year-old woman presents with a 48-hour history of fever, irrelevant talk, and two episodes of successive tonic-clonic seizures. Which of the following drugs can be administered while awaiting further investigations?

IV acyclovir. ### Explanation **Correct Option: D. IV Acyclovir** The clinical presentation of fever, altered mental status (irrelevant talk), and seizures in a young adult is highly suggestive of **Herpes Simplex Encephalitis (HSE)**, the most common cause of sporadic fatal encephalitis worldwide. In cases of suspected viral encephalitis, **IV Acyclovir** must be started empirically as soon as possible. Delay in treatment significantly increases mortality and long-term neurological morbidity. HSE typically involves the temporal lobes, leading to psychiatric symptoms and seizures. Because the prognosis depends heavily on the "door-to-needle" time for antiviral therapy, it is administered while awaiting definitive investigations like CSF PCR or MRI. **Analysis of Incorrect Options:** * **A. IV Mannitol:** While mannitol is used to reduce intracranial pressure (ICP), it is an adjunctive symptomatic treatment, not a primary therapy for the underlying pathology. * **B. IV Amphotericin B:** This is the treatment for fungal meningitis (e.g., Cryptococcal). Fungal infections usually present more subacutely and are more common in immunocompromised individuals. * **C. IV Penicillin:** While used for neurosyphilis or certain bacterial meningitides, the combination of acute fever and prominent behavioral changes/seizures points more strongly toward a viral etiology (HSE) than a bacterial one. **Clinical Pearls for NEET-PG:** * **Gold Standard Investigation for HSE:** CSF PCR for HSV DNA. * **Imaging Choice:** MRI is more sensitive than CT; look for "temporal lobe involvement" (hyperintensities). * **EEG Finding:** Periodic Lateralized Epileptiform Discharges (PLEDs) are characteristic of HSE. * **Mechanism of Acyclovir:** It is a guanosine analog that requires viral **thymidine kinase** for initial phosphorylation, making it highly selective for virus-infected cells.

Q: Skin testing with tuberculin-PPD is most widely used in screening for:

Latent M. tuberculosis infection. ### Explanation **1. Why the Correct Answer is Right:** The Tuberculin Skin Test (TST) or Mantoux test is based on a **Type IV (Delayed-type) Hypersensitivity reaction**. When PPD (Purified Protein Derivative) is injected intradermally, it triggers sensitized T-cells in individuals previously exposed to *M. tuberculosis*. The primary clinical utility of the TST is to identify individuals with **Latent Tuberculosis Infection (LTBI)**—those who are infected but do not have active disease. In these patients, the immune system has successfully "contained" the bacilli, but memory T-cells remain, leading to a positive skin reaction. **2. Why the Incorrect Options are Wrong:** * **Active TB (Option A):** While a TST can be positive in active TB, it is **not** a diagnostic tool for it. Diagnosis of active TB requires clinical, radiological, and microbiological (Sputum AFB/CBNAAT) evidence. Furthermore, up to 25% of patients with active TB may show a false-negative TST due to "anergy." * **Miliary and Overwhelming TB (Options C & D):** In severe, disseminated forms of tuberculosis, the body’s cell-mediated immunity is often profoundly suppressed or overwhelmed. This leads to a state of **anergy**, where the TST frequently yields a **false-negative** result despite a high bacterial load. **3. High-Yield Clinical Pearls for NEET-PG:** * **Reading the test:** Results are read after **48–72 hours**. Only the **induration** (palpable hardness) is measured, not the erythema. * **False Positive:** Most commonly caused by prior **BCG vaccination** or infection with Nontuberculous Mycobacteria (NTM). * **False Negative (Anergy):** Seen in malnutrition, HIV/AIDS, sarcoidosis, miliary TB, and recent viral infections (e.g., Measles). * **Alternative:** The **IGRA (Interferon-Gamma Release Assay)** is more specific than TST as it does not cross-react with the BCG vaccine.

Question 1

Which one of the following is true regarding HIV infection?

Accepted Answer

Following needle stick injury, infectivity is reduced by administration of nucleoside analogues.

Answer

CD4 counts are the best predictors of disease progression.

Answer

Infected T cells survive for a month in infected patients.

Answer

In latent phase, HIV has minimal replication.

Question 2

The Jarisch-Herxheimer reaction is typically seen during the treatment of which condition?

Accepted Answer

Syphilis

Answer

Impetigo

Answer

Erysipelas

Answer

Typhoid

Question 3

What is the most common site for intestinal tuberculosis?

Accepted Answer

Distal ileum

Answer

Jejunum

Answer

Sigmoid colon

Answer

Ascending colon

Question 4

A client is prescribed with Pentamidine IV for the treatment of Pneumocystis jirovecii pneumonia. Suddenly, the client develops a temperature of 101.5°F. Which of the following would this sign most likely indicate?

Accepted Answer

The client has developed another infection.

Answer

An overdosage of the medication.

Answer

The need for an additional dosage.

Answer

The client is experiencing the therapeutic effect of the medication.

Question 5

Which of the following statements is FALSE regarding Infectious mononucleosis?

Accepted Answer

Non-suppurative, painless lymphadenopathy

Answer

Maculopapular rash or petechial rash

Answer

Lymphocytosis is usually demonstrable, with >10% atypical lymphocytes

Answer

Transient bilateral upper lid edema

Question 6

Which is the commonest complication of Mumps in adults?

Accepted Answer

Orchitis

Answer

Encephalitis

Answer

Pancreatitis

Answer

Carditis

Question 7

Exposure to which of the following conditions necessitates passive immunization with standard immune serum globulin?

Accepted Answer

Hepatitis A

Answer

Rabies

Answer

Hepatitis B

Answer

Tetanus

Question 8

A 32-year-old woman presents with a 48-hour history of fever, irrelevant talk, and two episodes of successive tonic-clonic seizures. Which of the following drugs can be administered while awaiting further investigations?

Accepted Answer

IV acyclovir

Answer

IV mannitol

Answer

IV amphotericin B

Answer

IV penicillin

Question 9

Which of the following is true regarding Tuberculosis (TB) in HIV infection?

Accepted Answer

Faster progression of ATT

Answer

Less susceptibility to Anti-TB therapy (ATT)

Answer

Same susceptibility to ATT

Answer

TB is more common in AIDS

Question 10

Skin testing with tuberculin-PPD is most widely used in screening for:

Accepted Answer

Latent M. tuberculosis infection

Answer

Active TB

Answer

Miliary TB

Answer

Overwhelming TB

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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