Low bacterial metabolism as a central mechanism of antimicrobial resistance and potential therapeutic target of staphylococcal biofilms in ventricular assist device driveline infections.

Objectives: Ventricular assist device driveline infections are difficult-to-treat diseases due to high antimicrobial resistance (AMR) of microbial biofilms. Multiple mechanisms of biofilm AMR have been proposed based on simplified in vitro models and demonstrated limited clinical implications. This study aimed to re-evaluate mechanisms contributing to staphylococcal biofilm AMR encountered in driveline infections and identify translatable therapeutic targets.

Methods: A tunnel-based biofilm assay mimicking subcutaneous driveline infections was utilized to grow clinically relevant biofilms. Seven first-line antibiotics were investigated against biofilms formed by two staphylococcal laboratory reference strains. The importance of various biofilm AMR mechanisms was evaluated, including the barrier effect of the biofilm extracellular polymeric substance (EPS) matrix, high-cell-density growth, the presence of persister cells and repressed bacterial metabolism.

Results: The presence of the EPS matrix couldn't decisively explain staphylococcal biofilm AMR in driveline infections. High-density growth and repressed bacterial metabolism appeared to be vital for biofilm AMR. Parallel comparisons of bacterial metabolic states and AMR at different biofilm developmental stages suggested a strong and negative correlation. Population profiling of tunnel-based biofilm cells identified subpopulations with low metabolic activity. Enhancing ATP production of biofilm cells partially restored their susceptibility to antibiotics. Local application of the weakly metabolism-dependent antibiotic gentamicin, but not the strongly metabolism-dependent vancomycin successfully killed staphylococcal biofilms in the simulated driveline tunnel, further underscoring the central role of bacterial metabolic repression in biofilm AMR.

Conclusions: This study identified repressed bacterial metabolism as a central mechanism underpinning biofilm AMR and provided an effective therapeutic target for biofilm-associated driveline infections.