Infective Endocarditis Microbiology — MFDS Part 1 MCQ

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ModerateMicrobiologyInfective Endocarditis MicrobiologyMFDS Part 1

A patient is diagnosed with infective endocarditis, and the causative bacteraemia is considered to have arisen from the oral flora. Which bacterial group is most likely to be responsible?

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Correct answer: B — Viridans group streptococci

Viridans group streptococci are the best answer because they are commensal oral organisms and are characteristically associated with infective endocarditis following bacteraemia of oral origin. This includes species such as Streptococcus sanguinis, S. mitis and S. oralis. UK SDCEP guidance identifies oral streptococci as implicated in a substantial proportion of infective endocarditis cases. Staphylococcus aureus is an important, and commonly the leading, cause of infective endocarditis overall, but it is not the organism most characteristic of a specified oral source. Enterococcus faecalis is more often associated with gastrointestinal or genitourinary sources. Streptococcus pyogenes and Haemophilus influenzae are uncommon causes of infective endocarditis.

Reference: Scottish Dental Clinical Effectiveness Programme. Antibiotic Prophylaxis Against Infective Endocarditis: Implementation Advice, 2018. https://www.sdcep.org.uk/media/qvpj2kfb/sdcep-antibiotic-prophylaxis-implementation-advice.pdf