Antimicrobial activity of dalbavancin tested against Gram-positive organisms isolated from patients with infective endocarditis in US and European medical centres

Background The management of endocarditis requires aggressive and prolonged antimicrobial treatment. We evaluated the in vitro activity of dalbavancin against bacteria from patients with infective endocarditis. Methods A total of 626 Gram-positive organisms were collected from patients with a diagnosis of bacterial endocarditis in the USA (n = 222) and Europe (n = 404) from 2007 to 2017 via the SENTRY Antimicrobial Surveillance Program and were tested for susceptibility to dalbavancin and comparators by broth microdilution. Results The most common organisms were Staphylococcus aureus (48.4%), Enterococcus faecalis (19.6%) and viridans group streptococci (VGS; 12.5%). Dalbavancin and daptomycin showed complete activity (100.0% susceptibility per CLSI criteria) against S. aureus, but dalbavancin MIC values were 4- to 8-fold lower. Vancomycin, linezolid and teicoplanin were also active against all S. aureus when CLSI criteria were applied. Ceftaroline was active against all MSSA (MIC90 0.25 mg/L) and 78.4% of MRSA isolates at ≤1 mg/L. All E. faecalis isolates were susceptible to ampicillin, daptomycin and linezolid, whereas 97.6% of isolates were susceptible to dalbavancin (MIC90 0.06 mg/L) and 96.7% were susceptible to vancomycin (MIC90 2 mg/L). All VGS and CoNS isolates were susceptible to dalbavancin, daptomycin, vancomycin and linezolid. Against Enterococcus faecium, 65.7% of isolates were inhibited by ≤0.25 mg/L dalbavancin and 62.9% were vancomycin susceptible. Conclusions Dalbavancin exhibited potent in vitro activity against a large collection of Gram-positive isolates recovered from patients with endocarditis in US and European medical centres. These results support further investigations to determine the role of dalbavancin in the treatment of infective endocarditis.