Infectious Diseases Practice Questions

Q: A 15-year-old boy presents with a two-day history of fever, altered sensorium, and purpuric rash. On examination, the patient is stuporous with a blood pressure of 90/60 mm Hg and extensive palpable purpura on the legs. Which of the following is the most appropriate initial choice of antibiotic?

Ceftriaxone. **Explanation:** The clinical presentation of fever, altered sensorium, and a purpuric rash in an adolescent is highly suggestive of **Meningococcemia** (caused by *Neisseria meningitidis*). The presence of purpura and hypotension (90/60 mm Hg) indicates a medical emergency, likely progressing toward Waterhouse-Friderichsen syndrome. **1. Why Ceftriaxone is correct:** In cases of suspected bacterial meningitis or meningococcemia, **Ceftriaxone** (a third-generation cephalosporin) is the empirical drug of choice. It provides excellent coverage against *N. meningitidis*, *Streptococcus pneumoniae*, and *Haemophilus influenzae*. It has superior CSF penetration and a longer half-life, making it ideal for rapid stabilization in a suspected septic patient. **2. Why other options are incorrect:** * **Vancomycin:** While used empirically for resistant *S. pneumoniae* or MRSA, it does not cover *N. meningitidis* effectively as a monotherapy. * **Penicillin G:** Historically the drug of choice, but it is no longer used empirically due to increasing resistance and the need for a broader spectrum until the pathogen is confirmed. * **Ciprofloxacin:** Used primarily for **chemoprophylaxis** in close contacts of a patient with meningococcal disease, not for the acute treatment of the disease itself. **Clinical Pearls for NEET-PG:** * **Drug of choice for Chemoprophylaxis:** Rifampicin (most common), Ciprofloxacin (single dose), or Ceftriaxone (in pregnancy). * **Glass Test:** Non-blanching purpuric rashes are a hallmark of meningococcal septicaemia. * **Initial Management:** Always prioritize ABCs (Airway, Breathing, Circulation) and administer the first dose of antibiotics within the "Golden Hour" to reduce mortality.

Q: A 50-year-old male presents with a one-week history of fever, abdominal distention, and loss of appetite. The symptoms are unresponsive to antibiotics and antimalarials. The Widal test is negative, but the RK39 dipstick test is positive. Which of the following drugs can be used for treatment?

Amphotericin B. ### Explanation **Diagnosis:** The patient presents with classic signs of **Visceral Leishmaniasis (Kala-azar)**: prolonged fever, abdominal distention (suggestive of hepatosplenomegaly), and lack of response to routine antibiotics. The definitive diagnostic clue is the **positive RK39 dipstick test**, which is highly sensitive and specific for *Leishmania donovani* infection in the Indian subcontinent. **Why Amphotericin B is Correct:** **Liposomal Amphotericin B (LAmB)** is currently the **drug of choice** for Visceral Leishmaniasis according to WHO and National Vector Borne Disease Control Programme (NVBDCP) guidelines. It is highly effective, with a cure rate of >95% after a single dose (10 mg/kg) or short courses. It works by binding to ergosterol in the leishmanial cell membrane, creating pores that lead to cell death. **Analysis of Incorrect Options:** * **A. Bedaquiline:** An antitubercular drug that inhibits mycobacterial ATP synthase. It is specifically used for Multidrug-Resistant Tuberculosis (MDR-TB). * **B. Linezolid:** An oxazolidinone antibiotic used for Gram-positive infections (like MRSA and VRE) and as a second-line agent for TB. It has no activity against protozoa. * **C. Fluconazole:** An azole antifungal used for candidiasis and cryptococcal meningitis. While it targets ergosterol synthesis, it is ineffective against *Leishmania*. **High-Yield Clinical Pearls for NEET-PG:** * **Miltefosine:** The only **oral** drug available for Kala-azar; however, it is teratogenic (contraindicated in pregnancy). * **Sodium Stibogluconate (Pentavalent Antimonials):** Formerly the first-line treatment, but now largely abandoned in Bihar/India due to widespread resistance. * **Post-Kala-azar Dermal Leishmaniasis (PKDL):** Occurs in 5-10% of treated cases; Liposomal Amphotericin B is also the preferred treatment here, though for a longer duration. * **Drug of choice in pregnancy:** Liposomal Amphotericin B.

Q: Which of the following etiologic agents is the most common cause of infection in liver transplant patients?

Cytomegalovirus. **Explanation:** **Cytomegalovirus (CMV)** is the most common clinically significant viral pathogen in solid organ transplant (SOT) recipients, particularly liver transplant patients [2]. The risk is highest between **1 to 6 months post-transplant**, coinciding with peak immunosuppression [2]. CMV infection in liver transplant patients often manifests as "CMV syndrome" (fever, malaise, leukopenia) or tissue-invasive disease, most commonly causing **hepatitis** in the allograft. **Analysis of Options:** * **A. Candida:** While fungal infections are common in the early post-operative period (first 30 days) due to surgical complications or indwelling catheters, they are less frequent overall than CMV [2]. * **C. Herpes simplex virus (HSV):** HSV is common but usually presents as mucocutaneous lesions [1]. Due to the routine use of viral prophylaxis (like Acyclovir or Valganciclovir), its incidence is significantly lower than CMV [1], [2]. * **D. Pneumocystis jirovecii (PJP):** PJP is a potential opportunistic fungal infection; however, its incidence has drastically reduced due to the standard use of **Trimethoprim-Sulfamethoxazole (TMP-SMX)** prophylaxis [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Timeline of Infection:** * * 6 months:* Community-acquired infections [2]. * **Risk Factor:** The highest risk for CMV is a **Seronegative Recipient (R-) receiving an organ from a Seropositive Donor (D+)** [1]. * **Diagnosis:** Quantitative PCR for CMV DNA is the gold standard [2]. * **Treatment:** Intravenous **Ganciclovir** or oral Valganciclovir [1], [2].

Q: An asymptomatic adult with a CD4 count of 230/µL falls under which category of CDC classification?

A2. The CDC classification for HIV/AIDS (1993) is a high-yield topic for NEET-PG. It uses a matrix based on **Clinical Categories (A, B, C)** and **CD4+ T-lymphocyte counts (1, 2, 3)**. ### 1. Why A2 is Correct * **Clinical Category A:** Includes asymptomatic HIV infection, persistent generalized lymphadenopathy (PGL), or acute (primary) HIV infection [1]. Since the patient is **asymptomatic**, they fall into Category A [1]. * **CD4 Category 2:** Defined as a CD4 count between **200–499/µL** [1]. * Combining these, an asymptomatic patient with a CD4 count of 230/µL is classified as **A2**. ### 2. Why Other Options are Incorrect * **A1:** Incorrect because Category 1 requires a CD4 count of **≥500/µL** [1]. * **B2:** Incorrect because Category B involves "Symptomatic, not A or C" conditions (e.g., Oral Candidiasis, Herpes Zoster, Bacillary Angiomatosis) [1]. This patient is asymptomatic. * **C1:** Incorrect because Category C is reserved for **AIDS-defining illnesses** (e.g., PCP pneumonia, Esophageal Candidiasis, Kaposi Sarcoma) regardless of CD4 count. Also, Category 1 implies a CD4 count ≥500/µL. ### 3. High-Yield Clinical Pearls * **The "AIDS" Threshold:** Any patient in Categories **A3, B3, or C1-C3** (i.e., CD4 <200/µL OR the presence of an AIDS-defining illness) is clinically diagnosed with AIDS. * **WHO vs. CDC:** While the CDC uses CD4 counts, the **WHO Staging System** (used more commonly in India/NACO guidelines) is primarily clinical (Stages 1–4) [1]. * **Prophylaxis Tip:** For any patient with CD4 <200/µL (Category 3), start **Cotrimoxazole** prophylaxis for *Pneumocystis jirovecii*.

Q: What is the most common form of peripheral neuropathy associated with HIV infection?

Distal symmetric polyneuropathy. **Explanation:** **Distal Symmetric Polyneuropathy (DSPN)** is the most common neurological complication of HIV, affecting approximately 30–50% of patients, particularly those with advanced immunosuppression (low CD4 counts). It is a "length-dependent" axonal neuropathy characterized by a "stocking-glove" distribution of sensory loss, paresthesia, and burning pain [1]. The pathogenesis involves direct viral neurotoxicity, chronic inflammation, and historically, the use of "d-drug" NRTIs (Stavudine, Didanosine). **Analysis of Incorrect Options:** * **Autonomic Neuropathy:** While it occurs in HIV (causing orthostatic hypotension or GI dysmotility), it is far less common than DSPN and usually occurs in late-stage AIDS. * **Lumbosacral Polyradiculoneuropathy:** This is a rare, subacute syndrome typically caused by **CMV coinfection** when CD4 counts drop below 50 cells/mm³. It presents with cauda equina-like symptoms (saddle anesthesia, urinary retention). * **Multiple Mononeuropathy (Mononeuritis Multiplex):** This is less common and usually associated with vasculitis (early HIV) or CMV (late HIV). **High-Yield Clinical Pearls for NEET-PG:** 1. **Most common cause of DSPN in HIV:** HIV itself (viral proteins like gp120) or mitochondrial toxicity from NRTIs (Stavudine > Didanosine). 2. **Clinical Presentation:** Loss of ankle jerks and diminished vibratory sense in the toes are the earliest signs. 3. **Management:** The primary treatment is optimizing ART. For neuropathic pain, **Gabapentin, Pregabalin, or Amitriptyline** are first-line agents. 4. **Inflammatory Demyelinating Polyneuropathy (AIDP/CIDP):** Can occur during **seroconversion** or early HIV when the immune system is still robust.

Q: What is the most common extra-intestinal manifestation of amebiasis?

Amoebic liver abscess. **Amoebic Liver Abscess (ALA)** is the most common extra-intestinal manifestation of infection by *Entamoeba histolytica*. The parasite enters the portal circulation from the colon and travels to the liver, where it causes enzymatic necrosis of hepatocytes [1]. It is significantly more common in adult males (10:1 ratio) and typically presents as a solitary abscess in the **right lobe** of the liver. **Analysis of Options:** * **Amoebic Liver Abscess (Correct):** It occurs in approximately 1–10% of patients with invasive amebiasis. The classic "anchovy sauce" pus (reddish-brown, odorless) is a hallmark finding [1]. * **Pleural Effusion & Atelectasis (Incorrect):** These are secondary pulmonary complications. They usually occur due to sympathetic irritation of the diaphragm or direct rupture of a right-lobe liver abscess through the diaphragm into the pleural space. * **Cardiac Tamponade (Incorrect):** This is a rare but life-threatening complication caused by the rupture of an abscess located in the **left lobe** of the liver into the pericardial sac. **NEET-PG High-Yield Pearls:** 1. **Investigation of Choice:** Ultrasound is the initial screening tool, but **Contrast-Enhanced CT (CECT)** is more sensitive. 2. **Serology:** Enzyme-linked immunosorbent assay (ELISA) for antibodies is positive in >90% of cases. 3. **Treatment:** **Metronidazole** (or Tinidazole) is the drug of choice, followed by a luminal amebicide (e.g., Diloxanide furoate or Paromomycin) to eradicate the intestinal cyst carrier state. 4. **Aspiration Indications:** Only required if the abscess is large (>10cm), involves the left lobe (risk of rupture into pericardium), or fails to respond to medical therapy.

Q: Rose spots are seen in which of the following conditions?

Enteric fever. **Explanation:** **Enteric Fever (Correct Answer):** Rose spots are a classic, pathognomonic cutaneous manifestation of **Enteric fever** (caused by *Salmonella Typhi* and *Paratyphi*). These are small (2–4 mm), blanching, erythematous maculopapules typically found on the upper abdomen and lower chest. They appear during the **second week** of illness and occur in approximately 30% of cases. The spots represent bacterial emboli in the dermis; notably, *Salmonella* can be cultured from these lesions. **Why other options are incorrect:** * **Typhoid fever:** While Typhoid fever is a subset of Enteric fever, "Enteric fever" is the more comprehensive and clinically accurate term in this context as it encompasses both *S. Typhi* and *S. Paratyphi* (both of which cause rose spots) [2]. * **Typhus fever:** Caused by *Rickettsia*, it presents with a maculopapular rash that starts in the axillae and spreads to the trunk, but these are not referred to as "rose spots" [1]. * **Rheumatic fever:** This condition is associated with **Erythema Marginatum**, which are pink, evanescent, non-pruritic rings with central clearing, primarily on the trunk and limbs. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** Rose spots appear in the 2nd week (the "Week of Complications") [2]. * **Step-ladder pyrexia:** The characteristic fever pattern of Enteric fever. * **Faget’s Sign:** Relative bradycardia (pulse does not rise proportionally with temperature), a key diagnostic clue. * **Diagnosis:** Use the **BASU** mnemonic for culture positivity: **B**lood (1st week), **A**ntibody/Widal (2nd week), **S**tool (3rd week), **U**rine (4th week). Bone marrow culture is the most sensitive overall.

Question 1

A 50-year-old male patient with a history of sexually transmitted disease acquired 20 years ago presents with headache, seizures, confusion, and numbness in the extremities. What is the expected pupillary response in this patient?

Accepted Answer

The light reflex is absent, but the accommodation reflex is present.

Answer

Both light reflex and accommodation reflex are absent.

Answer

Both light reflex and accommodation reflex are present.

Answer

The light reflex is present, but the accommodation reflex is absent.

Question 2

A 15-year-old boy presents with a two-day history of fever, altered sensorium, and purpuric rash. On examination, the patient is stuporous with a blood pressure of 90/60 mm Hg and extensive palpable purpura on the legs. Which of the following is the most appropriate initial choice of antibiotic?

Accepted Answer

Ceftriaxone

Answer

Vancomycin

Answer

Penicillin G

Answer

Ciprofloxacin

Question 3

A 50-year-old male presents with a one-week history of fever, abdominal distention, and loss of appetite. The symptoms are unresponsive to antibiotics and antimalarials. The Widal test is negative, but the RK39 dipstick test is positive. Which of the following drugs can be used for treatment?

Accepted Answer

Amphotericin B

Answer

Bedaquiline

Answer

Linezolid

Answer

Fluconazole

Question 4

A 38-year-old homeless man presents with 2 days of shortness of breath, chills, fever, drooling, painful swallowing, and a 'croupy' cough. Physical examination reveals bluish discoloration of the skin and a tough, gray membrane adhered to the pharynx. What is the underlying mechanism through which this disease affects normal cells?

Accepted Answer

The process of protein synthesis is inhibited in the target cells.

Answer

DNA synthesis is inhibited in the target cells.

Answer

RNA synthesis is inhibited in the target cells.

Answer

The plasma membrane becomes leaky in the target cells.

Question 5

Which of the following etiologic agents is the most common cause of infection in liver transplant patients?

Accepted Answer

Cytomegalovirus

Answer

Candida

Answer

Herpes simplex virus

Answer

Pneumocystis jirovecii pneumonia

Question 6

Multiple sinuses and induration of the chest wall are likely due to which condition?

Accepted Answer

Pulmonary actinomycosis

Answer

Tuberculosis

Answer

Atypical mycobacterial infection

Answer

Tuberculosis in an HIV-AIDS patient

Question 7

An asymptomatic adult with a CD4 count of 230/µL falls under which category of CDC classification?

Accepted Answer

A2

Answer

A1

Answer

B2

Answer

C1

Question 8

What is the most common form of peripheral neuropathy associated with HIV infection?

Accepted Answer

Distal symmetric polyneuropathy

Answer

Autonomic neuropathy

Answer

Lumbosacral polyradiculoneuropathy

Answer

Multiple mononeuropathy

Question 9

What is the most common extra-intestinal manifestation of amebiasis?

Accepted Answer

Amoebic liver abscess

Answer

Pleural effusion

Answer

Atelectasis

Answer

Cardiac tamponade

Question 10

Rose spots are seen in which of the following conditions?

Accepted Answer

Enteric fever

Answer

Typhus fever

Answer

Typhoid fever

Answer

Rheumatic fever

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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