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Keywords:

  • accessory gene regulator;
  • antimicrobial therapy;
  • multidrug resistance;
  • photodynamic therapy

ABSTRACT

Photodynamic therapy (PDT) has been considered a feasible alternative for antimicrobial therapy of multidrug-resistant pathogens. However, bacterial response mechanisms against PDT-generated photo-oxidative stress remain largely unknown. Herein, it is shown that the accessory gene regulator Agr is involved in Staphylococcus aureus response to photo-oxidative stress generated by laser-induced PDT with the photosensitizer chlorin e6. Transcriptional profiling revealed that sublethal PDT induces a general stress response and also activates Agr-dependent gene regulation. Moreover, mutant S. aureus lacking Agr function showed hypersusceptibility to two independent PDT conditions with higher energy densities, demonstrating Agr-dependent S. aureus resistance against PDT.