Infectious Diseases Practice Questions

Q: A patient with a recent upper respiratory infection develops worsening facial pain, purulent nasal discharge, and tenderness over the maxillary sinuses. Symptoms have now persisted for more than 10 days without improvement. What is the most appropriate initial treatment?

Amoxicillin-clavulanate. ***Amoxicillin-clavulanate*** - Symptoms persisting >10 days with **purulent nasal discharge** and **facial pain** meet criteria for **acute bacterial rhinosinusitis**, making this the **first-line empirical antibiotic treatment**. - Provides broad-spectrum coverage against common pathogens including **Streptococcus pneumoniae**, **Haemophilus influenzae**, and **beta-lactamase producing organisms**. *Topical decongestant* - While it may provide temporary **symptomatic relief** by reducing nasal congestion, it does not address the underlying **bacterial infection**. - Prolonged use (>3-5 days) can lead to **rhinitis medicamentosa** with rebound congestion, worsening the clinical picture. *Antihistamine* - Primarily effective for **allergic rhinitis** by blocking histamine-mediated symptoms like sneezing and watery discharge. - **Ineffective against bacterial infections** and may worsen symptoms by drying mucous membranes and impairing **mucociliary clearance**. *Corticosteroid* - **Intranasal corticosteroids** may serve as adjunctive therapy to reduce inflammation but are insufficient as **monotherapy** for bacterial sinusitis. - Does not provide antimicrobial coverage needed for the suspected **bacterial pathogen** causing the persistent purulent symptoms.

Q: A 35-year-old woman presents with facial pain, nasal congestion, and purulent nasal discharge for 10 days. What is the most likely diagnosis?

Acute sinusitis. ***Acute sinusitis*** - The combination of **facial pain**, **nasal congestion**, and **purulent nasal discharge** for 10 days is highly characteristic of acute sinusitis, indicating inflammation and infection of the paranasal sinuses. - The persistence of symptoms for over 7-10 days, or worsening symptoms after initial improvement, supports a bacterial etiology rather than a self-limiting viral infection. *Migraine* - Migraines typically present with **unilateral, throbbing headache**, often accompanied by **photophobia, phonophobia**, and nausea, without purulent nasal discharge [1]. - While facial pain can occur, it's usually not associated with nasal congestion or discharge [1]. *Tension headache* - Tension headaches are usually characterized by **bilateral, pressing or tightening pain**, often described as a band around the head, and are not associated with nasal symptoms or purulent discharge [1]. - They typically lack the other features of sinusitis or migraines. *Trigeminal neuralgia* - This condition involves **sudden, severe, brief, stabbing or shock-like pain** in the distribution of the trigeminal nerve, often triggered by light touch or movement. - It does not present with nasal congestion or purulent discharge.

Q: A 25-year-old woman presents with a sudden onset of high fever, chills, and rigors. Blood cultures are pending. What is the next appropriate step in her management?

Administer broad-spectrum antibiotics. ***Administer broad-spectrum antibiotics*** - The patient presents with classic signs of **sepsis** (high fever, chills, rigors), which is a medical emergency requiring prompt intervention [2]. - **Early administration of broad-spectrum antibiotics** is crucial to improve outcomes and reduce mortality in suspected sepsis, even before culture results are available [1]. *Wait for blood culture results* - Delaying antibiotic treatment in a patient with suspected sepsis can lead to rapid clinical deterioration and increased mortality [1]. - While blood cultures are essential to guide definitive therapy, initial empiric broad-spectrum antibiotics should not be withheld [3]. *Start antipyretic therapy only* - Antipyretics only address the symptom of fever and do not treat the underlying infection causing the fever and chills. - This approach would leave the potentially life-threatening infection untreated, leading to worsening patient condition. *Order a CT scan* - A CT scan is not the immediate priority in a patient presenting with acute signs of systemic infection and suspected sepsis. - While it may be useful later to identify a source of infection, controlling the infection with antibiotics is the most urgent step.

Q: A 30-year-old male presents with chills and a high fever of 40°C. Which of the following symptoms would most likely suggest an infectious cause?

Rigors. ***Rigors*** - **Rigors** (generalized shivering with a sensation of cold) are strong indicators of a rapid and significant rise in body temperature, often seen with **bacteremia** or other severe infections [1]. - The body's defense mechanisms are fighting off a severe infection, leading to an exaggerated physiological response. *Excessive sweating* - **Excessive sweating (diaphoresis)** typically occurs as the body attempts to cool down during the defervescence (fever reduction) phase [1]. - While associated with fever, it is less specific for the *onset* or active phase of an infection compared to rigors [1]. *Skin rash* - A **skin rash** can be a symptom of certain infections (e.g., viral exanthems, meningococcemia) but is not a universal or primary indicator of *any* infectious cause [2]. - Many febrile illnesses do not present with a rash, and rashes can also be non-infectious in origin (e.g., allergic reactions). *Vomiting* - **Vomiting** can accompany many illnesses, both infectious (e.g., gastroenteritis, meningitis) and non-infectious (e.g., migraine, drug reaction). - It is a non-specific symptom that does not singularly point to an infectious etiology as strongly as rigors in the context of a high fever.

Q: A 35-year-old male presents with fever, night sweats, and unintentional weight loss over the past 3 months. He has a history of intravenous drug use. Most appropriate next step in the diagnosis?

HIV test. ***HIV test*** - The patient's **risk factors** (intravenous drug use) and constitutional symptoms (fever, night sweats, unintentional weight loss) are highly suggestive of **HIV infection**, [2], [5] which can lead to opportunistic infections or directly cause these symptoms. - An HIV test is crucial for **early diagnosis** and management to prevent progression to AIDS and initiate highly active antiretroviral therapy (HAART) [4]. *Chest X-ray* - While a Chest X-ray can detect pulmonary infections often associated with immunosuppression, it is a **secondary investigation** and not the most appropriate initial diagnostic step for the underlying cause of immunosuppression. - It would be more useful after identifying an underlying condition like HIV, especially if respiratory symptoms were prominent. *Tuberculin skin test* - Tuberculosis is a common opportunistic infection in immunocompromised individuals, including those with HIV, and can present with these symptoms [1]. - However, performing a **Tuberculin skin test** or **IGRA** is typically done after initial screening for HIV, as the interpretation relies on the patient's immune status. *Blood culture* - Blood cultures are useful for detecting **bacteremia or fungemia** and can help identify specific infections [3]. - While relevant for fever and night sweats, they are a **specific diagnostic test** for active bloodstream infection and do not address the underlying systemic cause of immunosuppression and constitutional symptoms like HIV.

Q: A patient with a fever presents with a heart rate of 120 beats per minute and a respiratory rate of 30 breaths per minute. What does this indicate?

Early sepsis. ***Early sepsis*** - A heart rate of 120 bpm (**tachycardia**) and a respiratory rate of 30 bpm (**tachypnea**) in the setting of fever meet the criteria for **Systemic Inflammatory Response Syndrome (SIRS)**, which can indicate early sepsis. - Sepsis is defined by life-threatening organ dysfunction caused by a dysregulated host response to infection, and these vital sign abnormalities are key indicators. *Tachypnea due to anxiety* - While anxiety can cause tachypnea and tachycardia, the presence of **fever** suggests an underlying infectious or inflammatory process rather than isolated anxiety. - Relying solely on anxiety as the cause without considering other indicators can lead to delayed diagnosis and treatment of serious conditions. *Expected response to fever* - While a moderate increase in heart rate and respiratory rate is expected with fever (e.g., 8-10 bpm increase per degree Celsius of fever), a heart rate of **120 bpm** and especially a respiratory rate of **30 bpm** are disproportionately elevated and exceed a typical physiological response. - These elevated vital signs signal a more significant physiological stress or dysregulation beyond a simple febrile response. *Normal physiological response to fever* - A "normal" physiological response to fever would involve a mild-to-moderate elevation in heart rate and respiratory rate; however, a heart rate of **120 bpm** and a respiratory rate of **30 bpm** are considered *abnormal* for a typical febrile response. - These values are sufficiently high to raise concern for **SIRS** or early sepsis, requiring further investigation.

Q: Which bacterial infection is characterized by a 'strawberry tongue'?

Scarlet fever. ***Scarlet fever*** - **Scarlet fever**, caused by **Group A Streptococcus**, is classically associated with a **strawberry tongue** due to inflamed papillae [1]. - Other characteristic symptoms include a **diffuse red rash** that feels like sandpaper, a sore throat, and fever [1]. *Impetigo* - **Impetigo** is a superficial skin infection characterized by **honey-colored crusted lesions**, typically on the face. - It does not involve systemic symptoms like fever or have oral manifestations such as a strawberry tongue. *Cellulitis* - **Cellulitis** is a deeper skin infection affecting the dermis and subcutaneous tissue, presenting as a **red, swollen, warm, and tender area of skin** [2]. - It does not cause a rash or a strawberry tongue; its manifestations are localized to the affected skin area [2]. *Erysipelas* - **Erysipelas** is a superficial form of cellulitis, characterized by a **sharply demarcated, raised, red, and warm rash**, often on the face or legs [2]. - While it's a skin infection, it does not involve the characteristic oral findings of a strawberry tongue.

Q: A 30-year-old male presents with high fever, muscle aches, and a history of swimming in freshwater lakes. Examination reveals schistosome cercariae on skin biopsy. What are the implications of this finding for potential systemic involvement?

Risk of hepatosplenic involvement. ***Risk of hepatosplenic involvement*** - The presence of **schistosome cercariae** indicates exposure to *Schistosoma* parasites, which can mature into adult worms and migrate to the **mesenteric veins**, leading to **hepatosplenic schistosomiasis** [1]. - Systemic involvement, particularly of the **liver and spleen**, is a well-known complication of schistosomiasis as eggs laid by adult worms can embolize to these organs, causing chronic inflammation and fibrosis [1]. *Localized skin reaction only* - While initial penetration of cercariae can cause a **localized dermatitis** (swimmer's itch), the presence of cercariae suggests a recent and significant exposure that could lead to systemic infection [1]. - This option overlooks the **life cycle** of *Schistosoma* parasites, which involves migration beyond the skin to internal organs once they transform into schistosomulae [1]. *No systemic involvement expected* - This statement is incorrect because **schistosome infection** is inherently a systemic disease once the cercariae successfully penetrate the skin and develop into schistosomulae [1]. - The adult worms reside in **venous plexuses**, and their eggs cause widespread inflammatory responses, leading to various systemic manifestations, including in the **gastrointestinal** and **urinary systems**, as well as the liver and spleen [1]. *Potential for CNS complications* - While **CNS complications** like **spinal cord schistosomiasis** or **cerebral schistosomiasis** can occur, they are less common forms of systemic involvement compared to hepatosplenic manifestations. - CNS involvement is usually due to **ectopic egg deposition** in the brain or spinal cord, which is a possible but not the most likely primary systemic implication.

Q: A 23-year-old male returns from a hiking trip with complaints of diarrhea, abdominal cramps, and fatigue. Stool microscopy reveals flagellated trophozoites. What is the most likely diagnosis?

Giardia lamblia. Giardia lamblia - The presence of flagellated trophozoites in a stool sample from a patient with a history of a hiking trip strongly points to Giardia lamblia infection, often acquired from contaminated water [1]. - Symptoms like diarrhea, abdominal cramps, and fatigue are characteristic of giardiasis, which can lead to malabsorption [1]. Entamoeba histolytica - While it causes diarrhea and abdominal pain, this parasite is identified by amoeboid trophozoites with pseudopods and often presents with bloody stools, not flagella [2]. - It can also cause liver abscesses, which is not indicated here [2]. Cryptosporidium hominis - This parasite is identified by its oocysts in stool samples, not flagellated trophozoites, and can cause severe, protracted watery diarrhea, particularly in immunocompromised individuals. - It does not present as a flagellated form in diagnostic samples. Trichomonas vaginalis - This is a flagellated parasite, but it primarily causes genitourinary infections and is found in the reproductive tract, not typically in stool samples causing gastrointestinal symptoms. - It is transmitted sexually and does not cause traveler's diarrhea.

Q: A 60-year-old male with a history of gardening presents with pneumonia and a nodular pulmonary infiltrate. A sputum sample grows filamentous bacteria that form branching rods. What is the likely pathogen, and what are the implications for treatment?

Nocardia spp.. Nocardia spp. - The combination of **pneumonia**, **nodular pulmonary infiltrate**, **gardening exposure** (soil organism), and **filamentous, branching rods** in sputum is highly characteristic of *Nocardia* infection. - *Nocardia* infections often require **prolonged treatment** with antibiotics such as **trimethoprim-sulfamethoxazole (TMP-SMX)** given its intracellular survival and tendency for recurrence. *Aspergillus spp.* - While *Aspergillus* can cause pulmonary infiltrates and is a filamentous fungus, it is typically described as having **hyphae with septations and acute-angle branching**, not bacterial rods [1]. - *Aspergillus* infections are often treated with **antifungal agents** like voriconazole, not antibiotics effective against bacteria. *Actinomyces spp.* - *Actinomyces* are also **filamentous branching bacteria**, but they are typically **anaerobic** and more commonly cause **cervicofacial** or **abdominal abscesses** with "sulfur granules," not usually pneumonia with nodular infiltrates in this clinical context. - *Actinomyces* infections are typically treated with **high-dose penicillin** for an extended period. *Mycobacterium tuberculosis* - *Mycobacterium tuberculosis* causes pulmonary disease and can lead to nodular infiltrates, but it is characterized as a **rod-shaped bacterium** that is **acid-fast**, not typically as filamentous or branching. - Treatment for **tuberculosis** involves a multi-drug regimen (e.g., RIPE therapy) for several months, which is distinct from the treatment for Nocardia.

Question 1

A patient with a recent upper respiratory infection develops worsening facial pain, purulent nasal discharge, and tenderness over the maxillary sinuses. Symptoms have now persisted for more than 10 days without improvement. What is the most appropriate initial treatment?

Accepted Answer

Amoxicillin-clavulanate

Answer

Corticosteroid

Answer

Antihistamine

Answer

Topical decongestant

Question 2

A 35-year-old woman presents with facial pain, nasal congestion, and purulent nasal discharge for 10 days. What is the most likely diagnosis?

Accepted Answer

Acute sinusitis

Answer

Migraine

Answer

Tension headache

Answer

Trigeminal neuralgia

Question 3

A 25-year-old woman presents with a sudden onset of high fever, chills, and rigors. Blood cultures are pending. What is the next appropriate step in her management?

Accepted Answer

Administer broad-spectrum antibiotics

Answer

Wait for blood culture results

Answer

Start antipyretic therapy only

Answer

Order a CT scan

Question 4

A 30-year-old male presents with chills and a high fever of 40°C. Which of the following symptoms would most likely suggest an infectious cause?

Accepted Answer

Rigors

Answer

Excessive sweating

Answer

Skin rash

Answer

Vomiting

Question 5

A 35-year-old male presents with fever, night sweats, and unintentional weight loss over the past 3 months. He has a history of intravenous drug use. Most appropriate next step in the diagnosis?

Accepted Answer

HIV test

Answer

Chest X-ray

Answer

Tuberculin skin test

Answer

Blood culture

Question 6

A patient with a fever presents with a heart rate of 120 beats per minute and a respiratory rate of 30 breaths per minute. What does this indicate?

Accepted Answer

Early sepsis

Answer

Tachypnea due to anxiety

Answer

Expected response to fever

Answer

Normal physiological response to fever

Question 7

Which bacterial infection is characterized by a 'strawberry tongue'?

Accepted Answer

Scarlet fever

Answer

Impetigo

Answer

Cellulitis

Answer

Erysipelas

Question 8

A 30-year-old male presents with high fever, muscle aches, and a history of swimming in freshwater lakes. Examination reveals schistosome cercariae on skin biopsy. What are the implications of this finding for potential systemic involvement?

Accepted Answer

Risk of hepatosplenic involvement

Answer

No systemic involvement expected

Answer

Localized skin reaction only

Answer

Potential for CNS complications

Question 9

A 23-year-old male returns from a hiking trip with complaints of diarrhea, abdominal cramps, and fatigue. Stool microscopy reveals flagellated trophozoites. What is the most likely diagnosis?

Accepted Answer

Giardia lamblia

Answer

Entamoeba histolytica

Answer

Cryptosporidium hominis

Answer

Trichomonas vaginalis

Question 10

A 60-year-old male with a history of gardening presents with pneumonia and a nodular pulmonary infiltrate. A sputum sample grows filamentous bacteria that form branching rods. What is the likely pathogen, and what are the implications for treatment?

Accepted Answer

Nocardia spp.

Answer

Aspergillus spp.

Answer

Actinomyces spp.

Answer

Mycobacterium tuberculosis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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