Characterization of the in vitro activity of novel lipoglycopeptide antibiotics

The increasing incidence of antibiotic resistance in human pathogens is of significant concern. Resistance to the widely-used and highly effective glycopeptide antibacterial agent vancomycin, which has been in clinical use for over half a century, has emerged in staphylococci and enterococci. This has spurred the development of newer glycopeptide agents, some of which show activity against vancomycin-resistant organisms. The newer agents currently being developed contain lipophilic side-chains, which distinguish them from vancomycin; as such, they are categorized as lipoglycopeptides. Oritavancin, telavancin, and dalbavancin are lipoglycopeptides in late-stage development to combat Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci. This unit describes methods that may be used to assess the in vitro activities of lipoglycopeptides. The methods include susceptibility assays, time-kill and time-kill-synergy assays, inhibition of synthesis of macromolecules, membrane perturbation assays, and measurement of activity against biofilms.