A child is admitted to the hospital with a suspected diagnosis of infective endocarditis. The child has been experiencing fever, malaise, anorexia, and a headache. The nurse knows that most common causative organism of infective endocarditis is?

Appeared in: NORCET -4 , 2023

Explanation

Streptococcus viridans is the most frequent cause of subacute bacterial endocarditis (SBE).
The patient's symptoms of fever, malaise, anorexia, and headache are classic signs of a subacute, insidious infection, which is characteristic of SBE.
Viridans streptococci are normal inhabitants of the mouth and can enter the bloodstream during dental work or even daily oral hygiene, seeding damaged heart valves.
In children, especially those with underlying congenital heart disease, S. viridans is a primary culprit for endocarditis.

Option B: Staphylococcus aureus typically causes acute bacterial endocarditis (ABE), which presents with a more severe and rapid onset (high fever, sepsis) than the subacute symptoms described in the question.
Option C: Clostridium perfringens is an anaerobic bacterium that is well-known for causing gas gangrene (myonecrosis) and food poisoning. It is not a typical causative agent of infective endocarditis.
Option D: While Haemophilus species are part of the HACEK group of organisms that can cause endocarditis, they are far less common than streptococci and staphylococci. Group B Haemophilus influenzae is more famously known for causing meningitis and epiglottitis in children.

Visual 1: Flowchart: Depicting the pathogenesis of subacute bacterial endocarditis, starting from oral bacteremia (e.g., dental procedure) to colonization of a damaged heart valve.
Visual 2: Infographic: Comparing the key features of Acute vs. Subacute Bacterial Endocarditis, highlighting the causative organisms, onset, and clinical signs.

Clinical Relevance

Nursing practice connection: Use the key finding related to Microbiology of Infective Endocarditis to guide bedside assessment, documentation, and the next nursing action.
Nurses must recognize the subtle, non-specific signs of subacute endocarditis (e.g., persistent low-grade fever, fatigue) to ensure timely diagnosis and treatment, preventing severe complications like heart failure or embolic stroke.
A key nursing role is patient education regarding prophylactic antibiotics before dental or other invasive procedures for high-risk individuals (those with prosthetic valves, previous endocarditis, or certain congenital heart defects).
What if the patient presented with a sudden high fever of 104°F, shaking chills, and hypotension? The priority suspicion would shift from S. viridans to S. aureus, indicating acute bacterial endocarditis, which requires more aggressive and immediate intervention.

How to Approach the Question

First, identify the key clinical diagnosis: 'suspected infective endocarditis'.
Next, analyze the patient's symptoms: 'fever, malaise, anorexia, and a headache'. Note that these are subacute, non-specific, and suggest a slow-developing illness.
The question asks for the 'most common' causative organism. This requires recalling the microbiology of endocarditis.
Differentiate between the pathogens that cause acute versus subacute endocarditis. The subacute symptoms in the stem are the critical clue.
Associate Streptococcus viridans with subacute presentations and Staphylococcus aureus with acute presentations.
Based on the subacute clinical picture, select Streptococcus viridans as the most likely causative agent.

Concept Tested & Keywords

Concept Tested: Microbiology of Infective Endocarditis
Stem keywords: infective endocarditis, child, fever, malaise, anorexia, headache, causative organism
Lead-in keywords: most common
Clinical cues: The constellation of symptoms (fever, malaise, anorexia, headache) points towards a subacute, rather than acute, infectious process.

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Practise the full NORCET -4 , 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.