Infectious Diseases Practice Questions

Q: Which of the following conditions are directly associated with HIV infection of tissues?

All of the above. HIV is not merely an immunosuppressive virus; it is a multisystemic pathogen that can directly infect and damage various tissues through viral proteins (like gp120 and Tat) and the resulting chronic inflammatory response [1]. 1. **Cardiomyopathy:** HIV can directly infect myocytes, leading to **HIV-associated cardiomyopathy**. The pathogenesis involves direct viral invasion, cytokine-mediated injury (TNF-alpha), and nutritional deficiencies. It typically presents as dilated cardiomyopathy with global left ventricular dysfunction. 2. **Enteropathy:** HIV directly infects the gut-associated lymphoid tissue (GALT) and intestinal epithelial cells. This leads to **HIV Enteropathy**, characterized by chronic diarrhea and malabsorption in the absence of secondary opportunistic infections [1]. It is caused by villous atrophy and increased intestinal permeability. 3. **Arthrofibromyalgia:** HIV is known to be associated with various rheumatological manifestations. While "Arthrofibromyalgia" is a specific term used here, HIV is directly linked to chronic musculoskeletal pain syndromes, fibromyalgia-like presentations, and reactive arthritis due to immune dysregulation and direct viral presence in synovial tissues. **Why "All of the above" is correct:** Each of these conditions can occur as a primary manifestation of the HIV virus itself, rather than being a secondary opportunistic infection (like CMV or Cryptosporidium) [1]. **High-Yield Clinical Pearls for NEET-PG:** * **HIV Nephropathy (HIVAN):** Typically presents as Collapsing Focal Segmental Glomerulosclerosis (FSGS), especially in patients of African descent. * **HIV Lipodystrophy:** Often associated with Protease Inhibitors (PIs), leading to "buffalo hump" and peripheral fat wasting. * **Neurological:** HIV can directly cause **AIDS Dementia Complex (ADC)** or HIV-associated neurocognitive disorder (HAND) via microglial infection [1].

Q: A 32-year-old male who recently visited a sea coast presented with an ulcer over the left leg. What is the probable causative organism?

Vibrio vulnificus. **Explanation:** The clinical presentation of a skin ulcer following exposure to seawater or coastal environments is a classic "high-yield" scenario pointing toward **Vibrio vulnificus**. **Why Vibrio vulnificus is correct:** *Vibrio vulnificus* is a gram-negative, halophilic (salt-loving) bacterium found in warm coastal waters. Infection typically occurs via two routes: ingestion of contaminated seafood (leading to septicemia) or **wound exposure to seawater**. It can cause aggressive soft tissue infections ranging from cellulitis and ulcers to life-threatening necrotizing fasciitis. Patients with underlying liver disease or iron overload are at particularly high risk for severe systemic dissemination. **Why other options are incorrect:** * **Pasteurella multocida:** Associated with animal bites or scratches, most commonly from **cats or dogs**, not seawater. * **Micrococcus halophillus:** While halophilic, this organism is generally considered non-pathogenic to humans and is not a recognized cause of marine-acquired leg ulcers. * **Neisseria gonorrhea:** Causes sexually transmitted infections. While it can cause disseminated gonococcal infection (DGI) with skin lesions (typically hemorrhagic papules or pustules), it is not associated with coastal exposure. **Clinical Pearls for NEET-PG:** * **Key Association:** Seawater exposure + Rapidly progressing skin lesion = *Vibrio vulnificus*. * **Risk Factor:** Chronic liver disease (Cirrhosis) or Hemochromatosis increases mortality risk significantly due to the organism's requirement for iron. * **Treatment:** The drug of choice is typically a combination of **Doxycycline and a third-generation Cephalosporin** (e.g., Ceftriaxone). * **Differential Diagnosis:** *Mycobacterium marinum* also causes "fish tank granuloma" after water exposure, but it presents as a chronic, indolent "sporotrichoid" nodules rather than an acute ulcer.

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

Lymph nodes. **Explanation:** Tuberculosis (TB) is a multisystemic disease caused by *Mycobacterium tuberculosis*. While the lungs are the primary site of infection, extrapulmonary tuberculosis (EPTB) occurs in approximately 15–20% of immunocompetent patients and up to 50% of HIV-positive individuals. **Why Lymph Nodes are correct:** Tuberculous lymphadenitis (Scrofula) is consistently documented as the **most common site** of extrapulmonary involvement worldwide [1]. It most frequently affects the cervical lymph nodes [1]. The pathogenesis usually involves lymphatic spread from a primary focus in the lungs or tonsils [3]. **Analysis of Incorrect Options:** * **B. Pleura:** Pleural TB is the second most common site in many regions. It typically presents as an exudative pleural effusion resulting from a delayed hypersensitivity reaction to mycobacterial antigens. * **C. Genitourinary tracts:** This was historically more common but now ranks lower than lymph node and pleural involvement. It often remains clinically silent for years before presenting with "sterile pyuria." * **D. Bones:** Skeletal TB (e.g., Pott’s spine) accounts for approximately 10% of EPTB cases [2]. While it is a significant cause of morbidity, it is less frequent than lymphatic involvement [1],[2]. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site of EPTB:** Lymph nodes (Cervical > Mediastinal) [1]. * **Most common site of Skeletal TB:** Spine (Pott’s disease), specifically the lower thoracic and upper lumbar vertebrae [2]. * **Most common site of CNS TB:** TB Meningitis (usually involving the base of the brain). * **Sterile Pyuria:** Always suspect Renal TB in a patient with pus cells in urine but negative routine bacterial cultures. * **HIV Association:** As CD4 counts decline, the incidence of EPTB (especially disseminated and lymph nodal forms) increases significantly.

Q: All of the following malignancies are associated with HIV, except?

Astrocytoma. **Explanation:** The association between HIV and malignancy is primarily driven by profound immunosuppression, chronic inflammation, and co-infection with oncogenic viruses [3]. HIV-associated malignancies are categorized into **AIDS-Defining Illnesses (ADIs)** and **Non-AIDS-Defining Cancers (NADCs)** [3]. **Why Astrocytoma is the correct answer:** Astrocytoma is a primary brain tumor that does not show an increased incidence in HIV-infected individuals. Unlike Primary CNS Lymphoma (which is strongly associated with HIV and EBV), astrocytomas are not linked to viral triggers or the specific immune deficits caused by HIV [2]. **Analysis of other options:** * **Kaposi’s Sarcoma (Option A):** An AIDS-defining illness caused by **HHV-8** [3]. It is the most common neoplasm in HIV patients and often spreads to the lungs [1]. * **Non-Hodgkin’s Lymphoma (Option B):** An AIDS-defining illness, particularly high-grade B-cell lymphomas (e.g., Burkitt’s, Diffuse Large B-cell Lymphoma) [3]. These are often associated with **EBV** [2]. * **Gastric Adenocarcinoma (Option D):** This is a **Non-AIDS-Defining Cancer (NADC)**. While not an ADI, studies show that HIV patients have a higher risk of various non-AIDS cancers, including gastric, lung, and anal cancers, due to chronic inflammation and lifestyle factors. **High-Yield Clinical Pearls for NEET-PG:** 1. **AIDS-Defining Malignancies:** Kaposi’s Sarcoma (HHV-8), Non-Hodgkin’s Lymphoma (EBV), and Invasive Cervical Carcinoma (HPV) [3]. 2. **Most common CNS tumor in HIV:** Primary CNS Lymphoma (EBV-related); must be differentiated from Toxoplasmosis [2]. 3. **Trend:** With the advent of HAART, the incidence of ADIs has decreased, but the incidence of NADCs (like Lung Cancer and Hodgkin’s Lymphoma) is rising as the HIV population ages.

Q: Hutchinson's triad consists of Hutchinson's teeth, 8th nerve deafness, and what else?

Interstitial keratitis. **Explanation:** Hutchinson’s triad is a classic clinical sign pathognomonic for **Late Congenital Syphilis** (usually manifesting after age 2). It consists of three specific findings: 1. **Hutchinson's teeth:** Blunted, notched, peg-shaped permanent incisors. 2. **8th Nerve Deafness:** Sensorineural hearing loss caused by labyrinthitis or auditory nerve involvement. 3. **Interstitial Keratitis:** Inflammation of the corneal stroma, leading to corneal scarring and potential blindness. This typically appears between ages 5 and 15. **Analysis of Incorrect Options:** * **B. Saddle nose:** This results from the destruction of the nasal septum (chondritis). While it is a classic feature of congenital syphilis, it is **not** part of the specific "triad." * **C. Clutton's joints:** This refers to symmetrical, painless swelling of the knees (hydrarthrosis). It is a late manifestation but distinct from the triad. * **D. Sabre tibiae:** This is the anterior bowing of the tibia due to chronic periostitis. Like the others, it is a high-yield sign of late congenital syphilis but falls outside the triad. **High-Yield NEET-PG Pearls:** * **Early Congenital Syphilis (<2 years):** Presents with snuffles (hemorrhagic rhinitis), pemphigus syphiliticus (bullous rash), and hepatosplenomegaly. * **Wimberger’s Sign:** Radiographic finding showing focal erosion of the medial aspect of the proximal tibial metaphysis. * **Mulberry Molars:** Permanent first molars with multiple poorly developed cusps (also seen in late congenital syphilis). * **Treatment of Choice:** Parenteral **Penicillin G** remains the gold standard for all stages of syphilis.

Q: What is the drug of choice for treating typhoid fever in pregnancy?

Ceftriaxone. **Explanation:** The management of typhoid fever (Enteric fever) in pregnancy requires a balance between maternal efficacy and fetal safety. **Why Ceftriaxone is the Correct Answer:** Third-generation cephalosporins, specifically **Ceftriaxone**, are currently the **drug of choice** for typhoid fever in pregnancy. This is due to two primary reasons: 1. **Safety Profile:** They are classified as FDA Category B drugs, meaning they have no known teratogenic effects and are safe for the developing fetus. 2. **Resistance Patterns:** There is widespread emergence of Multidrug-Resistant (MDR) *Salmonella typhi* (resistant to ampicillin, chloramphenicol, and cotrimoxazole) and Nalidixic Acid Resistant *S. typhi* (NARST). Ceftriaxone remains highly effective against these strains. **Analysis of Incorrect Options:** * **Ampicillin (A):** Historically used, but no longer the first line due to high rates of plasmid-mediated resistance (MDR strains). * **Chloramphenicol (B):** Avoided in pregnancy, especially near term, due to the risk of **"Gray Baby Syndrome"** in the neonate (caused by the infant's inability to conjugate the drug). It also carries a risk of bone marrow suppression. * **Ciprofloxacin (C):** Fluoroquinolones are generally contraindicated in pregnancy because they can cause **arthropathy** and permanent damage to the fetal cartilage (weight-bearing joints). **NEET-PG High-Yield Pearls:** * **Drug of choice for MDR Typhoid (General population):** Ceftriaxone or Azithromycin. * **Drug of choice for Uncomplicated Typhoid:** Azithromycin is increasingly preferred to limit Ceftriaxone resistance. * **Carrier State Treatment:** Ampicillin or Cholecystectomy (if gallstones are present). * **Widal Test:** Significant titers are usually >1:160 for O antigen and >1:160 for H antigen (O indicates recent infection).

Q: What does I.R.L.S. stand for?

Immune reconstitution inflammatory syndrome. **Explanation:** **Immune Reconstitution Inflammatory Syndrome (IRIS)** [1] is a clinical condition observed in HIV-infected patients where the immune system begins to recover after starting **Antiretroviral Therapy (ART)**, but then responds to a previously acquired opportunistic infection with an overwhelming inflammatory response. **1. Why Option C is Correct:** The term accurately reflects the pathophysiology: * **Immune Reconstitution:** The recovery of CD4+ T-cell counts and immune function following ART [1]. * **Inflammatory:** The clinical symptoms are caused by an exaggerated, "paradoxical" inflammatory response [1]. * **Syndrome:** A collection of signs/symptoms resulting from this immune flare. **2. Why Other Options are Incorrect:** * **Option A & B:** While "Idiopathic" or "Immunological" might sound plausible, they are not the standard medical nomenclature. The hallmark of the condition is the **inflammatory** damage to tissues. * **Option D:** This is a distractor that rearranges the words. The sequence must follow the physiological process: first the immune system reconstitutes, then the inflammation occurs. **Clinical Pearls for NEET-PG:** * **Pathogens:** Most commonly associated with *Mycobacterium tuberculosis*, *Cryptococcus neoformans*, and CMV. * **Two Types:** 1. **Paradoxical IRIS:** Worsening of a known infection already under treatment [1]. 2. **Unmasking IRIS:** Appearance of a previously undiagnosed (occult) infection [1]. * **Risk Factors:** Low baseline CD4 count (<50 cells/µL) and a rapid drop in viral load after starting ART [1]. * **Management:** Usually, ART is continued. Mild cases are treated with NSAIDs; severe cases (especially CNS involvement) require corticosteroids.

Q: Secondary pulmonary tuberculosis usually involves which part of the lungs?

Apex of lungs. **Explanation:** The correct answer is **B. Apex of lungs**. **1. Why the Apex is the Primary Site:** Secondary (reactivation) tuberculosis occurs in individuals who have been previously sensitized to *Mycobacterium tuberculosis* [1]. The organism is an **obligate aerobe**, meaning it thrives in environments with high oxygen tension. In an upright human, the apex of the lung has the highest **ventilation-perfusion (V/Q) ratio** [2]. Due to lower hydrostatic pressure at the top of the lungs, blood flow is significantly reduced compared to ventilation, resulting in the highest alveolar oxygen concentration ($P_AO_2$) in the body. This oxygen-rich environment provides the ideal milieu for the mycobacteria to proliferate. **2. Analysis of Incorrect Options:** * **A, C, and D (Base, Middle, and Lower Lobes):** These areas have higher blood flow but lower V/Q ratios and lower oxygen tension compared to the apices. While **Primary TB** often involves the lower or middle lobes (Ghon complex) [1] due to higher ventilation volume, **Secondary TB** specifically targets the apices (Simon’s foci). **3. Clinical Pearls for NEET-PG:** * **Location:** Secondary TB typically involves the **apical and posterior segments** of the upper lobes or the superior segment of the lower lobes [3]. * **Pathology:** Unlike primary TB, secondary TB is characterized by **cavitation** [3] due to a brisk delayed-type hypersensitivity (Type IV) response, which leads to tissue necrosis. * **Radiology:** Look for "cavitary lesions" in the infraclavicular or apical regions on a chest X-ray. * **Mnemonic:** "Secondary = Superior" (Upper lobes/Apex).

Q: Which of the following is true regarding tuberculous lymphadenitis?

All of the above. **Explanation:** Tuberculous lymphadenitis (TBLN) is the most common form of extrapulmonary tuberculosis, accounting for approximately 30–40% of cases. It occurs due to the lymphatic spread of *Mycobacterium tuberculosis*. **Analysis of Options:** * **Option A (History of contact):** While many cases represent reactivation of a latent infection, a significant number of patients (especially children) have a documented history of contact with an active pulmonary TB case. * **Option B (Demographics):** TBLN shows a bimodal age distribution but is most frequently encountered in children and young adults (typically under 30 years). In endemic regions like India, it is a primary cause of persistent lymphadenopathy in these age groups. * **Option C (Anatomic Site):** The **cervical lymph nodes** are involved in 60–90% of cases (traditionally termed "Scrofula"). The nodes are typically painless, firm, and may eventually become matted or form a cold abscess/sinus tract. Since all three statements accurately describe the clinical profile of the disease, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Fine Needle Aspiration Cytology (FNAC) is the initial investigation of choice, showing epithelioid granulomas with caseous necrosis. * **Gold Standard:** Culture of the lymph node tissue or biopsy. * **Imaging:** On CT, nodes often show **peripheral rim enhancement** with central low-attenuation (necrosis). * **Differential:** In children, non-tuberculous mycobacteria (NTM) can cause similar lymphadenopathy, but it is usually unilateral and lacks systemic symptoms. * **Paradoxical Upgrading:** During ATT, nodes may temporarily enlarge or new nodes may appear; this is an immune response, not treatment failure.

Question 1

Which of the following conditions are directly associated with HIV infection of tissues?

Accepted Answer

All of the above

Answer

Cardiomyopathy

Answer

Enteropathy

Answer

Arthrofibromyalgia

Question 2

A 40-year-old HIV-positive lady presented with multiple, discrete, firm lymphadenopathy in the posterior cervical and supraclavicular regions of 6 months duration. She also complained of chronic cough during this period. A surgical biopsy of the lymph nodes was diagnosed as TB lymphadenitis. Which statement is true in this setting?

Accepted Answer

Higher bacteriological yield from microscopy and culture is expected.

Answer

Granulomas in the lymph node biopsy specimen will be more numerous in this patient.

Answer

An important differential diagnosis is Kikuchi's disease.

Answer

Systemic symptoms are uncommon in HIV-infected persons due to associated pulmonary disease.

Question 3

A 32-year-old male who recently visited a sea coast presented with an ulcer over the left leg. What is the probable causative organism?

Accepted Answer

Vibrio vulnificus

Answer

Pasteurella multocida

Answer

Micrococcus halophillus

Answer

Neisseria gonorrhea

Question 4

What is the most common site for extrapulmonary tuberculosis?

Accepted Answer

Lymph nodes

Answer

Pleura

Answer

Genitourinary tracts

Answer

Bones

Question 5

All of the following malignancies are associated with HIV, except?

Accepted Answer

Astrocytoma

Answer

Kaposi's Sarcoma

Answer

Non-Hodgkin's lymphoma

Answer

Gastric adenocarcinoma

Question 6

Hutchinson's triad consists of Hutchinson's teeth, 8th nerve deafness, and what else?

Accepted Answer

Interstitial keratitis

Answer

Saddle nose

Answer

Clutton's joints

Answer

Sabre tibiae

Question 7

What is the drug of choice for treating typhoid fever in pregnancy?

Accepted Answer

Ceftriaxone

Answer

Ampicillin

Answer

Chloramphenicol

Answer

Ciprofloxacin

Question 8

What does I.R.L.S. stand for?

Accepted Answer

Immune reconstitution inflammatory syndrome

Answer

Immune reconstitution idiopathic syndrome

Answer

Immune reconstitution immunological syndrome

Answer

Inflammatory reconstitution immune syndrome

Question 9

Secondary pulmonary tuberculosis usually involves which part of the lungs?

Accepted Answer

Apex of lungs

Answer

Base of lungs

Answer

Middle lobes

Answer

Lower lobes

Question 10

Which of the following is true regarding tuberculous lymphadenitis?

Accepted Answer

All of the above

Answer

History of contact with TB patient may be present

Answer

Commonly seen in the young and children

Answer

Mostly in the cervical region

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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