Novel antimicrobial photodynamic agents active against epidemic methicillin-resistant Staphylococcus aureus

Abstract number: p1566

French  G., King  A., Shannon  K., Love  W.G., Rhys-Williams  W.


The rise of epidemic methicillin-resistant Staphylococcus aureus (EMRSA) and the emergence of mupirocin resistance means that it is essential to develop new therapies that cannot be readily overcome by microorganisms. The XF series of novel light activated antibacterial agents (1) active against Gram-positive bacteria addresses this issue and have superior levels of activity to antibiotics but with less likelihood of resistance emergence. The antibacterial activity of the XF Drugs against EMRSA has been investigated.


MIC and MBC assays were used to investigate the antibacterial activity of XF-73, a novel antimicrobial photodynamic agent against a range of Staphylococcus aureus strains. A concentration range of 2–0.001 mg/L was investigated. 15 minutes of 420 nm light activation (13 J/cm2) was applied. Light alone had no effect.


The results demonstrate that XF-73 has exceptionally low MIC and MBC values against all of the S. aureus strains tested. The results also demonstrate that XF-73 is equally effective against MRSA and methicillin-sensitive Staphylococcus aureus (MSSA) indicating its mode of action is independent of antibiotic resistance. XF-73 may therefore be useful in prevention and treatment of EMRSA. XF-73 is non-toxic to skin at prophylactic/therapeutic concentrations and has potential for the treatment of skin sepsis and the eradication of nasal and skin MRSA carriage. Work is in progress to evaluate the effectiveness of this compound in eradicating staphylococcal nasal carriage.


(1) Maisch T et al. Photodynamic effects of novel XF porphyrin derivatives on prokaryotic and eukaryotic cells. Antimicrob Agents Chemother 2005; 49: 1542–52.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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