Dalbavancin Alone and in Combination with Ceftaroline against Four Different Phenotypes of Staphylococcus aureus in a Simulated Pharmacodynamic/Pharmacokinetic Model

Glycopeptides such as vancomycin have been used as the first-line therapy against MRSA infections for over half a century. Reduced susceptibility and emergence of resistance to first-generation glycopeptides has led to development of second-generation lipoglycopeptide derivatives such as dalbavancin which hold broader ranges of activity and enhanced pharmacokinetic properties. We evaluated the MIC values for a total of 100 isolates, including 25 methicillin-resistant Staphylococcus aureus (MRSA), 25 heterogeneus vancomycin-intermediate S. aureus, 25 daptomycin nonsusceptible (DNS), and 25 vancomycin-intermediate S. aureus strains against dalbavancin, ceftaroline, and vancomycin alone and in combination. Dalbavancin was highly active against hVISA, DNS, and MRSA strains, achieving 96 to 100% susceptibility and 72% susceptibility against VISA strains. The combination of dalbavancin plus ceftaroline reduced dalbavancin MICs 62.5-fold and demonstrated enhanced killing against all four phenotypes in pharmacokinetic/pharmacodynamic models. Four strains of the aforementioned phenotypes were randomly chosen for pharmacodynamic/pharmacokinetic simulation models. Of interest, while both dalbavancin and vancomycin in combination with ceftaroline demonstrated significant improvement in glycopeptide fAUC/MIC values against these four phenotypes, the dalbavancin-ceftaroline combinations exhibited a 44- to 11,270-fold higher fAUC/MIC value in comparison to vancomycin-ceftaroline combinations. In addition, the time to detection limit was reduced for this combination (24 to 32 h) versus the vancomycin-ceftaroline combination (24 to 72h). To our knowledge, this is the first comprehensive study of dalbavancin and vancomycin combinations with ceftaroline. These data provide a novel approach for combating recalcitrant MRSA infections.