Photodynamic inactivation of methicillin-resistant Staphylococcus aureus on skin using a porphyrinic formulation

Márcia Braz, Diana Salvador, Ana T.P.C. Gomes*, Mariana Q. Mesquita, M. Amparo F. Faustino, M. Graça P.M.S. Neves, Adelaide Almeida

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Staphylococcus aureus is responsible for skin and soft tissue infections. Having in mind increased antibiotic resistance, in this study the efficacy of antimicrobial photodynamic therapy (aPDT) with a porphyrinic formulation (FORM) as photosensitizer (PS) to photoinactivate methicillin-resistant Staphylococcus aureus (MRSA) on skin was evaluated. Potassium iodide (KI) and iodopovidone (PVP-I) were also tested in combination with FORM as potentiator agents of FORM efficacy. The aPDT protocol was first developed in Phosphate Buffered Saline (PBS, in vitro). Porcine skin was artificially contaminated with MRSA (ex vivo) and treated with FORM, FORM + KI or FORM + PVP-I under white light. The in vitro results showed that FORM was effective to inactivate MRSA. A substantial reduction in the irradiation time, when compared to FORM alone, was observed for FORM + KI and FORM + PVP-I combinations. On skin, reductions in MRSA survival of 3.1 Log10 colony forming units (CFU) mL−1 were observed with FORM at 50 μM. Although the combined action of FORM + KI and FORM + PVP-I potentiated the aPDT efficacy in vitro, this was not observed ex vivo. Overall, the results showed that aPDT using FORM, even without coadjutants, is a promising approach for MRSA inactivation on skin.
Original languageEnglish
Article number101754
JournalPhotodiagnosis and Photodynamic Therapy
Publication statusPublished - Jun 2020
Externally publishedYes


  • Antimicrobial photodynamic therapy
  • Iodopovidone
  • Methicillin-resistant Staphylococcus aureus
  • Porphyrinic formulation
  • Potassium iodide
  • Potentiator agents


Dive into the research topics of 'Photodynamic inactivation of methicillin-resistant Staphylococcus aureus on skin using a porphyrinic formulation'. Together they form a unique fingerprint.

Cite this