Improvement of Antibacterial Efficacy Through Synergistic Effect in Photodynamic Therapy Based on Thiazinium Chromophores Against Planktonic and Biofilm-Associated Periodontopathogens.
OBJECTIVE
Aim of the study was to improve the antibacterial efficacy of toluidine blue (TBO)/methylene blue (MB)-mediated photodynamic systems with light-emitting diode (LED) or laser irradiation administered to planktonic and biofilm-associated periodontopathogens.


BACKGROUND DATA
Antibacterial photodynamic therapy (PDT) is a common, noninvasive adjunctive clinical method to inactivate microorganisms. So far, the disadvantage of this method has been its limited effectiveness in eliminating pathogens.


METHODS
An anaerobic cocktail consisting of six representative periodontal pathogens was prepared as initial culture for planktonic samples and biofilms grown on human tooth slides. Both types of microbial samples were exposed to three commercial photodynamic systems (PDT1: TBO, 630 nm LED, PDT2: TBO, 635 nm laser, PDT3: MB, 665 nm laser) in conventional and a new modified approach (PDTplus) based on the use of an oxygen supplement (photosensitizer+hydrogen peroxide). The microbial viability was characterized by bacterial growth [colony forming units (CFU)], total bacterial cell counts, and microbial vitality. Statistical data analysis was performed using 95% confidence intervals (ANOVA) and post hoc Tukey's test (p < 0.05).


RESULTS
The modified PDTplus showed the highest statistically significant synergistic antimicrobial activity for TBO-based systems evidenced by a CFU reduction of 9 log10 units to 0 for planktonic pathogens and a 4 log10 CFU reduction for biofilm bacteria. The MB-based PDTplus was superior mainly against biofilm pathogens. By comparison, the default TBO-based PDT achieved colony growth reductions of 2 and 1 log10 units concerning planktonic and biofilm cells.


CONCLUSIONS
Compared to conventional PDT, PDTplus showed superior antibacterial efficacy based on its synergistic effect, promising vast application possibilities.
['Decker|Eva-Maria|EM|', 'Bartha|Valentin|V|', 'von Ohle|Christiane|C|']
D000704:Analysis of Variance D000900:Anti-Bacterial Agents D018441:Biofilms D015169:Colony Count, Microbial D016001:Confidence Intervals D004357:Drug Synergism D013293:Enterococcus faecalis D006801:Humans D066298:In Vitro Techniques D008751:Methylene Blue D050296:Microbial Viability D010519:Periodontium D010778:Photochemotherapy D010933:Plankton D012016:Reference Values D014048:Tolonium Chloride D014081:Tooth Extraction
PDT periodontal pathogens modified PDT