Photodynamic antimicrobial effect of safranine O on an ex vivo periodontal biofilm.

BACKGROUND AND
OBJECTIVE: The increasing resistance of oral pathogens against antibiotic measures urgently requires new therapeutic strategies. In this context, antimicrobial photodynamic therapy (aPDT) may play a crucial part in the future. The aim of the present study was to compare the antibacterial efficiency of aPDT using the photosensitizer safranine O with that of chlorhexidine (0.2% CHX) on an ex vivo biofilm.
METHODS: First the antibacterial activity of both measures against planktonic cultures of Streptococcus gordonii ATCC 33399, Streptococcus mutans ATCC 25175, Fusobacterium nucleatum ATCC 10953, Aggregatibacter actinomycetemcomitans ATCC 33384 and Porphyromonas gingivalis ATCC 33277 was observed. Then a patient specific ex vivo biofilm was established from plaque and saliva samples of patients (n = 19) with chronic periodontitis. The antibacterial effects of aPDT and of 0.2% CHX were determined on the ex vivo biofilms cultivated for 24 and 72 hours. After cultivation of the treated samples on blood agar (2 days) the results were quantified by counting the colony forming units (cfu/ml).
RESULTS: Photodynamic treatment with safranine O showed a distinct antibacterial effect on F. nucleatum and P. gingivalis. Whereas S. gordonii was suppressed completely by aPDT, treatment with 0.2% CHX caused only a partial reduction. In the ex vivo biofilm model (24-hour biofilm), aPDT caused a significantly higher bacterial killing than treatment with 0.2% CHX. Compared to the untreated control, there was no significant difference on the 72-hour biofilm for both methods.
CONCLUSIONS: The results show that oral-pathogenic species in planktonic solution can be suppressed significantly by aPDT with safranine O. Especially for bacteria in a 24-hour ex vivo biofilm, this method is more effective than treatment with 0.2% CHX. Both antibacterial treatments did not show any significant effect on the biofilm cultivated for 72 hours.