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NVS Endocarditis — SCE Infectious Diseases MCQ

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HardBone & Joint InfectionNVS EndocarditisSCE Infectious Diseases

A 40-year-old man develops infective endocarditis with Abiotrophia defectiva (a nutritionally variant streptococcus — NVS). Blood cultures required special media (pyridoxal-supplemented agar) for growth. Why is this organism clinically significant in endocarditis?

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Correct answer: C — NVS endocarditis has higher relapse rates and treatment failure compared to typical viridans streptococcal endocarditis — Gentamicin should be added for the first 2 weeks (or longer) to the beta-lactam backbone

Nutritionally variant streptococci (Abiotrophia defectiva and Granulicatella species) cause endocarditis with notably higher treatment failure and relapse rates (up to 40%) compared to typical viridans streptococcal IE. This is attributed to: difficulty achieving bactericidal drug concentrations (high MBCs), biofilm formation, and tolerance to beta-lactams. ESC 2023 guidelines recommend treating NVS endocarditis as for Enterococcal IE: Benzylpenicillin (or Ampicillin) plus Gentamicin for at least 2 weeks, total course ≥4 weeks for NVE, ≥6 weeks for PVE.

Reference: ESC 2023 – Endocarditis; BSAC 2012 – Endocarditis; JCM 2019 – NVS