Infectious Diseases Practice Questions

Q: Which of the following diseases does not typically present with fever, rash, and lymphadenopathy?

Rheumatic fever. ### Original Explanation ***Rheumatic fever*** - While **fever** can be present, rheumatic fever is primarily characterized by migratory polyarthritis, carditis, chorea, erythema marginatum, and subcutaneous nodules, with a **rash (erythema marginatum)** being less common and not often accompanied by significant **lymphadenopathy** [1]. - Its etiology is linked to a prior **Streptococcus pyogenes infection** [1]. *Toxoplasmosis* - **Fever**, widespread **lymphadenopathy**, and a **maculopapular rash** are common features in acute toxoplasmosis, particularly in immunocompromised individuals. - Ocular and neurological involvement can also occur, distinguishing it from other conditions. *Rubella* - Known as **German measles**, it typically presents with a **low-grade fever**, a characteristic **maculopapular rash** that starts on the face and spreads downwards, and prominent **postauricular and occipital lymphadenopathy**. - It is a milder disease than measles but has significant implications during pregnancy. *Measles* - Characterized by **high fever**, a **maculopapular rash** that begins on the face and spreads, and significant **lymphadenopathy**, along with cough, coryza, and conjunctivitis (the "3 Cs") [2]. - **Koplik spots** on the buccal mucosa are pathognomonic for measles [2].

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: 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 patient with HIV presents with a chronic cough and weight loss. A chest X-ray shows bilateral interstitial infiltrates. What is the most likely cause?

Pneumocystis jiroveci pneumonia. ***Pneumocystis jiroveci pneumonia*** - **Pneumocystis jiroveci pneumonia (PJP)** is a common opportunistic infection in HIV patients, presenting with **chronic cough**, **weight loss**, and **bilateral interstitial infiltrates** on chest X-ray [1]. - The insidious onset and classic radiographic findings are highly suggestive of PJP, especially in individuals with advanced HIV [1]. *Kaposi's sarcoma* - While common in HIV, **Kaposi's sarcoma** typically manifests as **cutaneous lesions**, though it can affect internal organs, including the lungs. - Lung involvement usually presents with **nodular** or **peribronchial infiltrates** and sometimes **pleural effusions**, which differ from the diffuse interstitial pattern described [1]. *Mycobacterium avium complex* - **Mycobacterium avium complex (MAC)** infection in HIV patients typically causes **disseminated disease** with fever, weight loss, and anemia [2]. - Pulmonary MAC often presents with **nodular** or **cavitary lesions** on imaging, not bilateral interstitial infiltrates. *Cryptococcal meningitis* - **Cryptococcal meningitis** is a central nervous system infection causing **headache**, **fever**, and **altered mental status**, not primarily respiratory symptoms [1]. - While *Cryptococcus* can cause pulmonary disease (**cryptococcosis**), it's less common to present with chronic cough and exclusively interstitial infiltrates compared to PJP.

Q: A patient from a Lyme disease-endemic area presents with erythema migrans, fatigue, and arthralgia. Laboratory tests show positive IgM antibodies against Borrelia burgdorferi. Evaluate the stage of Lyme disease.

Early localized. ***Early localized*** - **Erythema migrans** is the hallmark rash of early localized Lyme disease, typically appearing within days to weeks of a tick bite [1]. - The presence of **fatigue** and **arthralgia** are non-specific symptoms that can occur at any stage, but along with positive **IgM antibodies**, are consistent with early infection. *Early disseminated* - This stage involves multiple erythema migrans lesions, **cranial nerve palsies** (e.g., Bell's palsy), **meningitis**, or **cardiac involvement** like AV block, none of which are described. - While fatigue and arthralgia can persist, the specific presentation points to the earliest stage before systemic spread with major organ involvement. *Late disseminated* - Characterized by chronic **arthritis** (especially in large joints), **encephalopathy**, or **neuropathy**, which typically develop months to years after the initial infection. - The patient's current symptoms are not indicative of these severe, chronic manifestations. *Post-Lyme disease syndrome* - Refers to persistent symptoms such as fatigue, joint pain, and cognitive difficulties lasting for more than 6 months after successful treatment of Lyme disease. - This patient presents with active infection symptoms, not chronic residual symptoms after treatment.

Q: An elderly man with a prosthetic heart valve presents with fever and a new heart murmur. Blood cultures grow gram-positive cocci in chains. What is the recommended management for this patient regarding valve replacement and antibiotic therapy?

Antibiotic therapy alone with penicillin.. The likely diagnosis is infective endocarditis caused by **Streptococcus viridans**, a common pathogen for **subacute endocarditis** on prosthetic valves [1]. Initial management typically involves empirical antibiotic therapy, and given the gram-positive cocci in chains and the clinical context, **high-dose penicillin** is often the preferred initial treatment for susceptible organisms [2]. While **ceftriaxone** is a broad-spectrum antibiotic, it is not the primary choice for suspected **Streptococcus viridans** endocarditis if penicillin-sensitive. **Valve monitoring alone** is insufficient, as active infection requires aggressive antibiotic treatment to prevent complications. **Anticoagulation** is not a primary treatment for infective endocarditis and can increase the risk of **hemorrhagic complications**, especially if there are vegetations or systemic embolization [3]. It does not address the underlying bacterial infection. **Immediate valve replacement** is generally reserved for cases with severe valvular dysfunction, large vegetations, recurrent emboli, or persistent infection despite adequate antibiotics [3]. While **vancomycin** is appropriate for methicillin-resistant bacteria, **penicillin** is preferred for penicillin-susceptible streptococci due to its efficacy and lower toxicity profile.

Q: What is the initial step in the management of a patient with suspected meningitis following neurosurgery?

Administer empirical antibiotics. Administer empirical antibiotics - In suspected post-neurosurgical meningitis, empirical antibiotics should be initiated promptly to cover likely pathogens, given the high morbidity and mortality associated with delayed treatment [1]. - Delaying antibiotics for diagnostic procedures can worsen outcomes, especially if the patient's condition is deteriorating [1]. *Conduct a lumbar puncture* - While a lumbar puncture (LP) is crucial for definitive diagnosis, it should typically be performed *after* empirical antibiotics have been started, especially if there's a risk of intracranial pressure or focal neurological deficits. - An LP may be contraindicated or need careful consideration until imaging rules out mass effect, but delaying antibiotics for LP alone is generally not recommended in this critical situation. *Perform a CT scan of the head* - A CT scan is important to rule out mass lesions, hydrocephalus, or other surgical complications *prior* to a lumbar puncture, especially in neurosurgical patients. - However, performing a CT scan should not delay the administration of empirical antibiotics, which is the immediate priority in suspected meningitis. *Monitor neurological status* - Monitoring neurological status is an ongoing and essential part of managing any neurosurgical patient, including those with suspected meningitis. - However, mere monitoring is not an *initial step* in intervention; rather, it informs the urgency and effectiveness of active treatments like antibiotic administration.

Q: A patient with chronic hepatitis B is being evaluated for antiviral therapy. Recent lab results show high HBV DNA levels and normal ALT levels. What is the most appropriate next step in management?

Consider starting antiviral therapy immediately. Consider starting antiviral therapy immediately - **High HBV DNA levels** in a patient with chronic hepatitis B, even with normal ALT, indicate an **active viral replication** phase [1]. - This scenario often represents **HBeAg-positive (immune tolerant) phase** or early **HBeAg-negative (immune active) disease**, where treatment is often warranted to prevent progression to cirrhosis and hepatocellular carcinoma [1]. *Monitor liver function tests closely before deciding* - While monitoring ALT is important, **high HBV DNA levels** indicate ongoing viral activity and potential for liver damage, even if current ALT is normal [1]. - Delaying therapy based solely on normal ALT could miss an opportunity to prevent **long-term complications**. *Switch to a different antiviral agent if necessary* - This option is relevant for patients already on therapy who are experiencing **treatment failure** or resistance, which is not indicated here as the patient is being evaluated for *initiation* of therapy. - There is no mention of prior antiviral treatment, so switching agents is not applicable. *Perform a liver biopsy to assess fibrosis* - A liver biopsy can provide information about the degree of inflammation and fibrosis, but it is an **invasive procedure** and often reserved for cases where the decision to treat is not clear-cut based on non-invasive markers. - In cases of high viral load, treatment is often initiated regardless of biopsy findings, and **non-invasive tests** (e.g., FibroScan) are increasingly preferred for fibrosis assessment.

Q: A patient presents with diarrhea following a course of broad-spectrum antibiotics. Stool tests positive for toxin B DNA. What is the best management approach?

Initiate oral vancomycin treatment. ***Initiate oral vancomycin treatment*** - The patient's symptoms (diarrhea post-antibiotics) and positive **toxin B DNA** indicate **Clostridioides difficile infection (CDI)** [1]. - **Oral vancomycin** is a first-line treatment for CDI due to its bioavailability in the GI tract, effectively targeting the bacteria [2]. *Continue current antibiotics* - Continuing the **broad-spectrum antibiotics** would likely exacerbate the CDI by further disrupting the normal gut flora [3]. - The current antibiotics are the probable cause of the initial **gut dysbiosis** allowing *C. difficile* to proliferate [1]. *Switch to a different antibiotic* - Switching to another broad-spectrum antibiotic is unlikely to treat CDI effectively and may even worsen the condition. - CDI requires specific treatment with agents like **vancomycin** or **fidaxomicin** that target *C. difficile* [2]. *Recommend probiotics only* - While probiotics can sometimes help restore normal gut flora, they are **insufficient as a sole treatment** for established CDI. - Probiotics do not directly eradicate *C. difficile* and are not a substitute for targeted antibiotic therapy in symptomatic infection.

Question 1

Which of the following diseases does not typically present with fever, rash, and lymphadenopathy?

Accepted Answer

Rheumatic fever

Answer

Toxoplasmosis

Answer

Rubella

Answer

Measles

Question 2

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 3

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 4

A patient with HIV presents with a chronic cough and weight loss. A chest X-ray shows bilateral interstitial infiltrates. What is the most likely cause?

Accepted Answer

Pneumocystis jiroveci pneumonia

Answer

Kaposi's sarcoma

Answer

Mycobacterium avium complex

Answer

Cryptococcal meningitis

Question 5

A patient from a Lyme disease-endemic area presents with erythema migrans, fatigue, and arthralgia. Laboratory tests show positive IgM antibodies against Borrelia burgdorferi. Evaluate the stage of Lyme disease.

Accepted Answer

Early localized

Answer

Early disseminated

Answer

Late disseminated

Answer

Post-Lyme disease syndrome

Question 6

A 35-year-old man presents with an eschar following a recent hike in a scrub typhus-endemic area. Despite initial doxycycline therapy, the patient remains febrile after 48 hours. What is the most appropriate next step?

Accepted Answer

Evaluate for antibiotic resistance and consider alternative antibiotics

Answer

Increase the doxycycline dose

Answer

Switch to a third-generation cephalosporin

Answer

Add azithromycin to the treatment regimen

Question 7

An elderly man with a prosthetic heart valve presents with fever and a new heart murmur. Blood cultures grow gram-positive cocci in chains. What is the recommended management for this patient regarding valve replacement and antibiotic therapy?

Accepted Answer

Antibiotic therapy alone with penicillin.

Answer

Valve monitoring with ceftriaxone.

Answer

Anticoagulation therapy with heparin.

Answer

Immediate valve replacement and vancomycin therapy.

Question 8

What is the initial step in the management of a patient with suspected meningitis following neurosurgery?

Accepted Answer

Administer empirical antibiotics

Answer

Conduct a lumbar puncture

Answer

Perform a CT scan of the head

Answer

Monitor neurological status

Question 9

A patient with chronic hepatitis B is being evaluated for antiviral therapy. Recent lab results show high HBV DNA levels and normal ALT levels. What is the most appropriate next step in management?

Accepted Answer

Consider starting antiviral therapy immediately

Answer

Monitor liver function tests closely before deciding

Answer

Switch to a different antiviral agent if necessary

Answer

Perform a liver biopsy to assess fibrosis

Question 10

A patient presents with diarrhea following a course of broad-spectrum antibiotics. Stool tests positive for toxin B DNA. What is the best management approach?

Accepted Answer

Initiate oral vancomycin treatment

Answer

Continue current antibiotics

Answer

Switch to a different antibiotic

Answer

Recommend probiotics only

Infectious Diseases — MCQs

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