Evaluating the potential for resistance development to antimicrobial blue light (at 405 nm) against Gram-negative bacteria: in vitro and in vivo studies

With the increasing number of pathogenic microbes that are becoming resistant to routinely used antimicrobials, it is important to look to non-traditional approaches for the treatment of infections. Antimicrobial blue light (aBL;405 nm) is a novel strategy for the treatment of infections. Here we report an investigation into the potential for resistance development to aBL in three clinically important Gram-negative bacteria, through sequential exposure in vitro and in vivo. We found that 20 cycles of aBL exposure, in vitro, did not incur resistance development, in any of the species tested (Acinetobacter baumanii, Pseudomonas aeruginosa or Escherichia coli). In addition, sub-curative sequential aBL treatment of a wound infected with a bioluminescent variant of the P. aeruginosa PAO1 strain, did not influence sensitivity to aBL. In conclusion, it is unlikely that sequential treatment of aBL will result in resistance generation, suggesting that multiple treatments of aBL may be administered without resistance development becoming a concern.