Telavancin shows superior activity to vancomycin with multidrug-resistant Staphylococcus aureus in a range of in vitro biofilm models

Abstract

The activity of telavancin was compared with vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) in planktonic culture and biofilms grown using a range of in vitro models. Antibiotic efficacy was determined using 24 clinical isolates, including healthcare-associated (HA)-MRSA, community-associated (CA)-MRSA and isolates with reduced (intermediate) susceptibility to vancomycin (VISA). Activity against biofilms was compared using three models: 96-peg plates, 96-well flat-bottom plates and a flow-cell system. Cell death was evaluated using a metabolic dye and Live/Dead staining. The planktonic minimum inhibitory concentration (MIC) range for telavancin was lower than that for vancomycin (0.06-0.25 mg/l and 0.5-8 mg/l, respectively). Vancomycin (100 × MIC) killed, on average, 59% of cells in HA-MRSA biofilms grown on 96-peg plates, 44% of cells in CA-MRSA biofilms and 26% of cells in VISA biofilms. Telavancin (100 × MIC) killed, on average, 63%, 49% and 41% of cells, respectively. The antibiotics showed similar efficacy against MRSA biofilms but telavancin was more effective against those formed by VISA isolates. In the flow-cell system, antibiotic cell killing was enhanced with both antibiotics, killing up to 80% of biofilm-associated cells. The variance in cell killing displayed when biofilms were grown using different systems highlights the importance of selecting an appropriate model for antimicrobial efficacy tests. The flow-cell system more closely reflects conditions encountered during infection and is possibly more clinically relevant than a 96-well plate system. Despite differences between the models evaluated, telavancin typically demonstrated improved efficacy over vancomycin, indicating the potential value of the agent in the treatment of biofilm-mediated infections caused by S. aureus, especially multidrug-resistant isolates.