Causative agent of bacterial endocarditis?

JIPMER Pondicherry NO - 2022

Applied Microbiology & Infection control

Easy

Appeared in: JIPMER Pondicherry NO - 2022

Explanation

Infective endocarditis (IE) is most commonly caused by Gram-positive cocci, specifically bacteria from the Staphylococcus and Streptococcus genera.
Staphylococcus aureus is the leading cause of acute IE, known for its high virulence and ability to damage heart valves rapidly.
Viridans group streptococci, which are normal flora of the oral cavity, are the classic cause of subacute IE, often following dental procedures in patients with pre-existing valve conditions.
Together, staphylococci and streptococci account for over three-quarters of all infective endocarditis cases, making this option the most comprehensive and accurate answer.

Option B: MRSA (Methicillin-Resistant Staphylococcus aureus) is a specific type of staph bacteria. While it is a serious cause of endocarditis, it represents only a subset of all staphylococcal infections. The broader category 'Staph and strep bacteria' is more encompassing.
Option C: Clostridium species are anaerobic bacteria that are well-known for causing conditions like tetanus, botulism, and gas gangrene. They are an extremely rare cause of infective endocarditis.
Option D: Wuchereria bancrofti is not a bacterium; it is a parasitic filarial worm. It is transmitted by mosquitoes and causes lymphatic filariasis (elephantiasis), a disease affecting the lymphatic system.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of Bacterial Endocarditis as background academic context rather than a clinical decision trigger.
Identifying the causative organism in endocarditis is critical for selecting the correct antibiotic therapy, which is often long-term (4-6 weeks) and intravenous.
Nurses play a key role in prevention by maintaining sterile technique for IV lines, providing oral hygiene, and educating at-risk patients about the need for antibiotic prophylaxis before certain procedures (e.g., dental work).
A patient's history provides crucial clues to the likely pathogen. For example, a history of IV drug use points towards Staphylococcus aureus, while a recent dental procedure suggests Viridans streptococci.

How to Approach the Question

First, identify the core concept of the question, which is the 'causative agent' of 'bacterial endocarditis'. This is a factual recall question.
Access your knowledge of microbiology and cardiovascular pathology. Recall the most common bacteria associated with heart infections.
Evaluate the options. 'Staph and strep bacteria' represents the two major groups responsible for the vast majority of cases.
Analyze the distractors. Recognize that MRSA is a specific type of Staph, making the broader category a better answer.
Eliminate options that are clearly incorrect. Clostridium causes different types of infections, and Wuchereria bancrofti is a parasite, not a bacterium.
Conclude that the most comprehensive and accurate answer is the one that includes the two most common bacterial groups.

Concept Tested & Keywords

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E6 Medicine Davidson Principles Practice 24e p. 548-550

E6 Microbiology OneStop Sastry p. 59-61