Infectious Diseases Practice Questions

Q: A 45-year-old man presents with a clean minor wound from gardening. His vaccination record shows he completed primary tetanus immunization series in childhood and received his last tetanus booster 12 years ago. What is the next step in management?

Single-dose Tetanus toxoid (TT) vaccine. **Single-dose Tetanus toxoid (TT) vaccine** - For a **clean, minor wound** in a patient who has completed their primary series but received their last booster 12 years ago, a single dose of **tetanus toxoid (TT)** or **TDaP** is indicated [1]. - Booster doses are recommended every **10 years** for tetanus-diphtheria protection. *Tetanus Immunoglobulin (TIG) with TT booster.* - **Tetanus Immunoglobulin (TIG)** is typically reserved for **dirty or contaminated wounds**, or for individuals with an **uncertain or incomplete vaccination history**, which is not the case here. - Giving TIG for a clean wound with a complete primary series would be over-treatment and unnecessary. *No further management required.* - The patient's last booster was **12 years ago**, exceeding the recommended 10-year interval for tetanus protection. - This makes him susceptible to tetanus, even from a clean wound, so **further management is required** [1]. *Complete tetanus vaccination series.* - A **complete tetanus vaccination series** is only needed for individuals who have an **incomplete or unknown** primary vaccination history. - This patient has a documented history of a completed primary series, so only a booster dose is required.

Q: Which viral infection is known to resemble the clinical features of erythroblastosis?

Parvovirus B19. **Parvovirus B19** - Parvovirus B19 preferentially infects and destroys **erythroid progenitor cells** in the bone marrow, leading to varying degrees of anemia [1]. - In a fetus, this can manifest as **hydrops fetalis**, severe anemia, and **heart failure**, mirroring the severe hemolytic anemia seen in erythroblastosis fetalis caused by Rh incompatibility. *Epstein-Barr Virus (EBV)* - While EBV can cause various hematologic complications, it is not known to directly mimic the severe **erythroid aplasia** or hydrops fetalis associated with erythroblastosis. - EBV is primarily associated with **infectious mononucleosis**, which involves atypical lymphocytes and mild anemia, not destruction of red cell precursors. *Cytomegalovirus (CMV)* - CMV can cause **congenital infections** with a wide range of manifestations, including microcephaly, sensorineural hearing loss, and hepatosplenomegaly. - Although CMV can cause **anemia**, it does not typically cause the profound **erythroid aplasia** or hydrops that specifically resembles erythroblastosis. *Herpes Simplex Virus (HSV)* - HSV infection in neonates can cause severe disseminated disease, **encephalitis**, or localized skin, eye, and mouth disease. - HSV does not primarily target **erythroid precursors** or cause significant hemolytic anemia that would mimic erythroblastosis.

Q: A bone marrow transplant recipient patient developed a chest infection. On HRCT, a 'tree-in-bud' appearance is seen. The most likely causative agent is:

TB. ***TB*** - A **'tree-in-bud' pattern** on HRCT is highly characteristic of **bronchiolar impaction** due to infection, classically seen in active **tuberculosis**. [1] - In an immunocompromised patient like a **bone marrow transplant recipient**, TB can rapidly disseminate and present with such radiographic findings. *Klebsiella* - **Klebsiella pneumonia** typically causes a **lobar pneumonia** with characteristic **bulging fissures** and severe consolidation. - It does not commonly present with a **'tree-in-bud' pattern** but rather extensive alveolar involvement. *Pneumocystis* - **Pneumocystis jirovecii pneumonia (PJP)** often presents with **diffuse ground-glass opacities** and **interstitial infiltrates**, predominantly in the perihilar region. [1] - A **'tree-in-bud' pattern** is not a typical radiographic feature of PJP. [1] *RSV* - **Respiratory Syncytial Virus (RSV)** typically causes **bronchiolitis** and **pneumonia**, especially in young children and immunocompromised adults. - While it can cause airway inflammation, a distinct **'tree-in-bud' pattern** is not its hallmark; rather, it often shows **peribronchial thickening** and **mucous plugging**.

Q: Tuberculosis of spine most commonly affects which vertebral segment?

Lower dorsal. ***Lower dorsal*** - The **lower dorsal** (thoracic) spine, especially T9-T12, is the most frequently affected segment in **tuberculosis of the spine** (Pott's disease) [1]. - This region's rich vascular supply, particularly the nutrient arteries, makes it a common site for hematogenous spread of *Mycobacterium tuberculosis*. *Upper dorsal* - While other segments can be affected, the **upper dorsal spine** is less commonly involved than the lower dorsal region. - Involvement here might present with similar symptoms but is statistically less frequent. *Lumbar* - The **lumbar spine** is the second most common site for spinal tuberculosis, but it is still less frequent than the lower dorsal region [1]. - Lumbar involvement typically presents with **low back pain** and neurological deficits but is not the primary site. *Cervical* - **Cervical spine** involvement in tuberculosis is rare, accounting for a small percentage of all spinal TB cases. - It can lead to severe neurological compromise due to the **narrow spinal canal** in this region.

Q: What is the commonest form of plague?

Bubonic plague. ***Bubonic plague*** - This is the **most common** form of plague, accounting for the majority of human cases [1]. - It is characterized by the development of painful, swollen lymph nodes called **buboes**, typically in the groin, armpit, or neck. *Pneumonic plague* - This form affects the **lungs** and is less common, but it is the most **virulent** and can be transmitted directly from person to person via respiratory droplets [1]. - If left untreated, bubonic or septicaemic plague can progress to secondary pneumonic plague [1]. *Septicaemic plague* - This form occurs when the bacteria **multiply in the bloodstream**, leading to widespread infection and potentially septic shock [1]. - It is less common than bubonic plague and can occur as a primary infection or as a complication of untreated bubonic plague [1]. *Hemorrhagic plague* - While plague can cause **hemorrhage** due to disseminated intravascular coagulation, "hemorrhagic plague" is not a distinct, recognized form of plague. - Bleeding is a **symptom** that can occur in severe cases of septicaemic or pneumonic plague, indicating extensive organ damage.

Q: Which of the following organisms is not typically associated with causing chronic adrenal insufficiency?

Mycobacterium bovis. ***Mycobacterium bovis*** - While *Mycobacterium bovis* can cause tuberculosis-like disease, it is **less commonly associated with chronic adrenal insufficiency** compared to *M. tuberculosis* itself, which has a predilection for adrenal tissue. - Infection with *M. bovis* primarily affects cattle and can be transmitted to humans, but its tropism for the adrenal glands leading to insufficiency is not a primary recognized feature. *Mycobacterium tuberculosis* - **Tuberculosis** is a well-known cause of chronic adrenal insufficiency, also known as **Addison's disease**, particularly in endemic regions. [1] - The bacteria can directly infect and destroy the adrenal cortex, leading to impaired hormonal production. *Histoplasma capsulatum* - **Disseminated histoplasmosis**, especially in immunocompromised individuals, can directly involve the adrenal glands. - This fungal infection can lead to **adrenal destruction and chronic adrenal insufficiency** by granuloma formation and necrosis. *Coccidioides immitis* - **Disseminated coccidioidomycosis** is another fungal infection that can cause adrenal gland involvement. - Similar to histoplasmosis, it can lead to **granulomatous inflammation and necrosis** within the adrenal cortex, resulting in chronic adrenal insufficiency.

Q: Which of the following characteristics does NOT apply to the rash of chickenpox when differentiating it from smallpox?

Deep-seated. ***Deep-seated*** - The rash of chickenpox is typically **superficial**, affecting the epidermis and upper dermis, leading to vesicles that are easily ruptured [1]. - In contrast, a **deep-seated** rash is characteristic of smallpox, where lesions extend into the deeper dermis, giving them a firm, "shotty" feel upon palpation. *Not centripetal* - This statement is generally true for chickenpox; its rash distribution tends to be **centrifugal**, meaning it is more concentrated on the trunk and extremities, sparing the face and distal limbs [1]. - Smallpox, however, is characterized by a **centripetal distribution**, with lesions most concentrated on the face and extremities. *Monomorphic* - This characteristic does NOT apply to chickenpox. Chickenpox exhibits a **pleomorphic rash**, meaning lesions at various stages of development (macules, papules, vesicles, scabs) are present simultaneously [1]. - A **monomorphic rash**, where all lesions are at the same stage of development, is a hallmark of smallpox. *Superficial* - This characteristic **applies** to chickenpox [1]. The lesions are typically superficial, affecting the epidermal layers and leading to a fragile, easily ruptured vesicle. - Smallpox lesions, in contrast, are **deep-seated**, firm, and umbilicated.

Q: Which of the following is a known risk factor for cholangiocarcinoma?

Clonorchis sinensis infestation. ***Clonorchis sinensis infestation*** - **Clonorchis sinensis**, also known as the Chinese liver fluke, is a well-established and significant risk factor for the development of **cholangiocarcinoma**. - Chronic inflammation and irritation of the bile ducts caused by the parasite are believed to promote malignant transformation. *Giardia lamblia (intestinal protozoa) infection* - **Giardia lamblia** is a common intestinal parasite causing giardiasis, characterized by diarrhea and malabsorption. - While it affects the gastrointestinal tract, there is **no known association** between *Giardia* infection and an increased risk of cholangiocarcinoma. *Paragonimus westermani infestation* - **Paragonimus westermani** is a lung fluke that primarily causes paragonimiasis, affecting the lungs and leading to cough and hemoptysis. - This parasite is not associated with direct bile duct inflammation or an increased risk of **cholangiocarcinoma**. *Ascaris lumbricoides (roundworm) infection* - **Ascaris lumbricoides** is a large intestinal roundworm that can cause intestinal obstruction or nutrient deficiencies. - Although it can occasionally migrate into the biliary tree, it is **not considered a risk factor** for cholangiocarcinoma [1].

Q: Non-parasitic eosinophilia is caused by infection with -

Coccidioidomycosis (Valley Fever). ***Coccidioidomycosis (Valley Fever)*** - **Coccidioidomycosis** is a systemic fungal infection that characteristically causes **non-parasitic eosinophilia**. This is a classic association frequently tested. - The host immune response to this specific fungal pathogen often involves a significant increase in **eosinophil count**. *Ehrlichiosis* - **Ehrlichiosis** is a bacterial infection transmitted by ticks, which typically causes **leukopenia** (low white blood cell count), sometimes with relative lymphocytosis. - While it affects various blood cell lines, it does not characteristically lead to **eosinophilia**; rather, it's more associated with low platelet and white cell counts. *Candidiasis (Yeast infection)* - **Candidiasis** is a common fungal infection, but it almost never causes **eosinophilia** [1]. - Systemic candidiasis is more likely to cause **neutrophilia**, rather than an increase in eosinophils [1]. *Staphylococcal infection* - **Staphylococcal infections** are bacterial and typically cause **neutrophilia** as the primary response.

Question 1

A 45-year-old man presents with a clean minor wound from gardening. His vaccination record shows he completed primary tetanus immunization series in childhood and received his last tetanus booster 12 years ago. What is the next step in management?

Accepted Answer

Single-dose Tetanus toxoid (TT) vaccine

Answer

No further management required.

Answer

Tetanus Immunoglobulin (TIG) with TT booster.

Answer

Complete tetanus vaccination series.

Question 2

Which viral infection is known to resemble the clinical features of erythroblastosis?

Accepted Answer

Parvovirus B19

Answer

Cytomegalovirus (CMV)

Answer

Epstein-Barr Virus (EBV)

Answer

Herpes Simplex Virus (HSV)

Question 3

A bone marrow transplant recipient patient developed a chest infection. On HRCT, a 'tree-in-bud' appearance is seen. The most likely causative agent is:

Accepted Answer

TB

Answer

Pneumocystis

Answer

Klebsiella

Answer

RSV

Question 4

Following are the features of neuropathy associated with varicella-zoster infection, which of the following is true?

Accepted Answer

Shingles are distributed along sensory dermatomes.

Answer

Upon reactivation, the virus is transported along sensory nerves to the skin, causing neuropathic symptoms.

Answer

Intranuclear inclusions, a hallmark of herpesvirus infections, are found in the peripheral nervous system during VZV neuropathy.

Answer

Persistent infection in neurons of sensory ganglia is a key feature of varicella-zoster virus pathophysiology.

Question 5

Tuberculosis of spine most commonly affects which vertebral segment?

Accepted Answer

Lower dorsal

Answer

Upper dorsal

Answer

Lumbar

Answer

Cervical

Question 6

What is the commonest form of plague?

Accepted Answer

Bubonic plague

Answer

Pneumonic plague

Answer

Septicaemic plague

Answer

Hemorrhagic plague

Question 7

Which of the following organisms is not typically associated with causing chronic adrenal insufficiency?

Accepted Answer

Mycobacterium bovis

Answer

Histoplasma capsulatum

Answer

Coccidioides immitis

Answer

Mycobacterium tuberculosis

Question 8

Which of the following characteristics does NOT apply to the rash of chickenpox when differentiating it from smallpox?

Accepted Answer

Deep-seated

Answer

Not centripetal

Answer

Monomorphic

Answer

Superficial

Question 9

Which of the following is a known risk factor for cholangiocarcinoma?

Accepted Answer

Clonorchis sinensis infestation

Answer

Giardia lamblia (intestinal protozoa) infection

Answer

Ascaris lumbricoides (roundworm) infection

Answer

Paragonimus westermani infestation

Question 10

Non-parasitic eosinophilia is caused by infection with -

Accepted Answer

Coccidioidomycosis (Valley Fever)

Answer

Ehrlichiosis

Answer

Candidiasis (Yeast infection)

Answer

Staphylococcal infection

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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