Infective endocarditis caused by penicillin-resistant viridans group streptococci: a series of nine cases from a Spanish cohort.

This article focuses on infective endocarditis (IE) caused by penicillin-resistant (PEN-R; minimum inhibitory concentration ≥4 mg/L) viridans and gallolyticus group streptococci (VGS-GGS), based on a retrospective analysis of 1563 streptococcal IE cases from 40 Spanish hospitals between 2008 and 2023. PEN-R VGS-GGS IE was rare (0.58%) and exclusively involved the Streptococcus mitis group, with higher rates of mitral valve involvement, surgical indication, and in-hospital mortality compared to penicillin-susceptible or intermediate strains. Antimicrobial treatment was heterogeneous but generally included beta-lactam combinations with aminoglycosides or daptomycin, and all patients undergoing cardiac surgery were cured. The study highlights the therapeutic challenges posed by PEN-R VGS-GGS IE and calls for further research to optimize effective and less toxic antimicrobial regimens.