title: Multiresistant strains are as susceptible to photodynamic inactivation as their naïve counterparts: protoporphyrin IX-mediated photoinactivation reveals differences between methicillin-resistant and methicillin-sensitive Staphylococcus aureus strains.
abstract: OBJECTIVE
  The current study was aimed at the investigation of differences in response to photoinactivation between methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) isolates. Moreover, we aimed to elucidate if the observed variation resulted from antimicrobial resistance mechanisms and strains' susceptibility to antibiotic therapy.
  
  
  BACKGROUND
  Because of the emergence of multidrug resistance, the development of alternative antimicrobial strategies seems to be required. The concept of photodynamic inactivation (PDI) involves cell exposure to appropriate wavelength light that leads to the excitation of photosensitizer molecules, resulting in the production of reactive oxygen species responsible for cell inactivation and death. Recently, we have demonstrated a strain-dependent response of S. aureus to photoinactivation, and observed elevated resistance to PDI among MRSA strains. Nevertheless, the mechanism underlying this phenomenon remains unexplained.
  
  
  METHODS
  S. aureus response to protoporphyrin IX (PPIX)-mediated photoinactivation was studied for 424 MRSA/MSSA isolates. VITEK 2 Advanced Expert System was used to detect antimicrobial resistance mechanisms and strains' susceptibility to antibiotictherapy.
  
  
  RESULTS
  Data obtained demonstrated that MRSA are significantly more resistant to photoinactivation than MSSA strains; however, the difference observed did not result from antimicrobial susceptibility or resistance mechanisms. Furthermore, regardless of the strains' origin, a similar effectiveness of PDI could be achieved. Moreover, it was determined that the ability to form biofilms in vitro, and the presence of mec element, does not explain the observed differences between MRSA and MSSA strains.
  
  
  CONCLUSIONS
  PDI could be highly effective against multidrug resistant pathogens as well as their naïve counterparts. Nevertheless, regardless of the antimicrobial resistance mechanism, the difference in response to PDI between MRSA and MSSA exists.
authors: 1 Laboratory of Molecular Diagnostics, Department of Biotechnology, Intercollegiate Faculty of Biotechnology University of Gdansk and Medical University of Gdansk , Gdansk, Poland .
authors: Mariusz
authors: M
authors: Grinholc
authors: Aleksandra
authors: A
authors: Rapacka-Zdonczyk
authors: Bartosz
authors: B
authors: Rybak
authors: Florian
authors: F
authors: Szabados
authors: Krzysztof P
authors: KP
authors: Bielawski
mesh_terms: D008164:Luminescent Proteins / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011524:Protoporphyrins / Q000494:pharmacology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects*
chemical_list: D008164:Luminescent Proteins; D017319:Photosensitizing Agents; D011524:Protoporphyrins; C028025:protoporphyrin IX