Human serum induces daptomycin tolerance in and viridans group streptococci.

Daptomycin is a membrane-targeting lipopeptide antibiotic used in the treatment of infective endocarditis caused by multidrug-resistant Gram-positive bacteria such as , enterococci and viridans group streptococci. Despite demonstrating excellent activity and a low prevalence of resistant isolates, treatment failure is a significant concern, particularly for enterococcal infection. We have shown recently that human serum triggers daptomycin tolerance in , but it was not clear if a similar phenotype occurred in other major infective endocarditis pathogens.