Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

Cell metabolic repression as a key mechanism underpinning antimicrobial resistance of staphylococcal biofilms (104397)

Yao Sun 1 2 3 4 , David McGiffin 5 , Anton Y. Peleg 3 4 , Yue Qu 3 4
  1. Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
  2. Wenzhou Medical University-Monash Biomedicine Discovery Institute Alliance in Clinical and Experimental Biomedicine, Wenzhou medical university, Wenzhou, Zhejiang, China
  3. Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Victoria, Australia
  4. Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
  5. Department of Cardiothoracic Surgery, The Alfred and Monash University, Melbourne, Victoria, Australia

Background: Medical device-related infections are extremely difficult to treat, due to the high antimicrobial resistance (AMR) of associated biofilms. Several mechanisms of biofilm resistance have been proposed using simplified in vitro biofilm models and had only limited clinical implications. We aimed to re-assess the importance of various mechanisms that may contribute to AMR of biofilms encountered in clinical environments.

Methods: A tunnel-based biofilm assay mimicking ventricular assist device driveline infections was used to culture clinically relevant biofilms of staphylococci. Seven first-line antibiotics of different classes were selected. Various mechanisms were assessed for their roles in biofilm AMR, including the barrier effects of extracellular polymeric substances (EPS) matrix, high-density growth mode, quorum sensing, global stress responses, tolerant and persister sub-populations, and cell metabolic repression.

Results: EPS appeared to only play a strain- and antimicrobial-dependent role on biofilm AMR. Disarming quorum sensing system of mature staphylococcal biofilms did not restore their susceptibilities to vancomycin and oxacillin. Global stress responses and highly dense growth mode of biofilms were associated with not only biofilm AMR, but lower metabolic activities of biofilm cells. Analyses of cell metabolic activities and biofilm AMR at different biofilm developmental stages found a negative correlation between cell metabolism and biofilm AMR. More importantly, stimulating cell ATP production in biofilms significantly restored biofilm sensitivities to antibiotics. A weakly metabolism-dependent antibiotic such as gentamicin at 1024 ug/mL, but not the strongly metabolism-dependent vancomycin readily eradicated mature staphylococcal biofilms, further supporting a key role of cell metabolic repression in biofilm AMR. Population analysis of tunnel-based staphylococcal biofilms found a small fraction of persister cells that also had low cellular metabolic activities.

Conclusions: This study identified cell metabolic repression as a key mechanism underpinning biofilm AMR and a promising therapeutic target for these troublesome infections.