The rise in antibiotic-resistant organisms has made treating and managing bacterial skin infections difficult [1]. Current antimicrobials are becoming less effective, creating an urgent need for viable solutions [2]. To address this issue, a primary recommendation is to promote early-stage drug discovery, emphasizing the need for models that deliver rapid and consistent results for evaluating new antimicrobial compounds as they transition from in vitro to in vivo studies. In response, we have designed an in vitro model to mimic a wound infection using modified agar-based plates (MABP) along with bioluminescent bacteria and a bioluminescent imaging system to screen the efficacy of antimicrobial compounds rapidly.
The developed model used 5 % blood agar channel as the infection site and placed it on 2 % agar. Using this model, we determined the efficacy of polymyxin B and mupirocin against gram-negative bacteria K. pneumoniae Xen39 and P. aeruginosa Xen41 and MRSA SAP231, respectively. BLI enabled continuous monitoring of bacterial presence throughout the infection period. The efficacy of the compounds was determined by measuring photon intensity at the channel and quantifying the viable bacterial count at the experiment's conclusion. Additionally, these models provided a visual representation of compound effectiveness within a short timeframe through bioluminescence images. Treatment was administered 2 hours post-infection, and its effectiveness was evaluated after 2 hours post-treatment.
Bioluminescence imaging revealed that radiance levels dropped to the background level after treatment for all the strains. The photon intensity and the viable bacteria count was also notably reduced in the treatment group compared to the non-treatment group.
In summary, we have successfully established the MABP as an in vitro model, enabling faster compound screening through visual bioluminescence images, applicable to both Gram-positive and Gram-negative bacteria. This model can be used to evaluate the efficacy of novel compounds for treating bacterial infections.