Evaluation of antibacterial effect of photodynamic therapy with different photosensitizers on omadacycline resistant bacteria isolated from superficial skin Infections in Egyptian tertiary hospital

Background: The recent emergence of multi-drug resistant (MDR) bacteria necessitates coordinated efforts, particularly in developing countries, to replace the administration of antibiotics with alternative therapeutic modalities such as photodynamic inactivation employing different photosensitizers (PSs). So, we aim to valuate the in-vitro effect of Photodynamic therapy using PS alone and PS combined with light‐emitting diode (LED) light on the colony count of isolated Omadacycline resistant organisms. Methods: A total of 300 clinical samples were obtained from superficial skin infections. Omadacycline resistant microorganisms were identified & subjected to PSs (methylene blue (MB), New methylene blue N (NMBN) and Toluidine blue O (TBO)) alone and Antimicrobial photodynamic therapy (aPDT) using PSs and LED. Results: All tested isolates showed antibacterial effect in the form of reduction in colony count after treatment with different photosensitizers with different concentrations at different durations. S.aureus isolates showed the lowest mean colony count between 3.46 to 4.25 log10 CFU/ml after treatment with all photosensitizers followed by Klebsiella then E.coli and lastly Pseudomonas. The reduction in colony count increased with longer duration of PDT and higher PSs’ concentration. Conclusion: Comparing the three PSs, the present study showed that TBO was the most effective PS on all isolates.