Energy dose parameters affect antimicrobial photodynamic therapy-mediated eradication of periopathogenic biofilm and planktonic cultures.
OBJECTIVE
This study evaluated the in vitro efficacy of a commercially available aPDT system in eradication of the periopathogens Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans in both planktonic and biofilm cultures.


BACKGROUND
Antimicrobial photodynamic therapy (aPDT) is an effective antibacterial approach in vitro; however, few data are available regarding effective light-energy parameters.


METHODS
Planktonic and biofilm cultures of periopathogens were exposed to a methylene blue-based formulation and irradiated with a 670-nm nonthermal diode laser. Energy doses were varied from 2.3 to 9.4 J/cm(2) through adjustments in illumination time and a constant power density. Controls consisted of no treatment, light only, and photosensitizer only. Temperature changes were recorded in experimental samples before and after illumination.


RESULTS
aPDT with an energy dose of 9.4 J/cm(2) was effective in eradicating P. gingivalis, F. nucleatum, and A. actinomycetemcomitans in biofilm and planktonic form. Reductions from control in planktonic cultures at this energy dose were 6.8 +/- 0.7, 5.2 +/- 0.6, and 1.9 +/- 0.6 log(10), respectively, whereas biofilm reductions were 4.5 +/- 1.2, 3.4 +/- 1.1, and 4.9 +/- 1.4 log(10). Decreasing the treatment time produced an energy dose-dependent killing effect in both models. Changes in sample temperature did not exceed 3 degrees C under these exposure parameters.


CONCLUSIONS
This study demonstrated that three important periopathogens are susceptible to aPDT-mediated killing, regardless of whether they are present in planktonic or biofilm form. Furthermore, a clear energy dose-dependence exists with this treatment that should to be taken into account when determining optimal treatment times in clinical application.
Street
Cale N
CN
Ondine Research Laboratories, Bothell, Washington 98011, USA. cstreet@ondinebiopharma.com
Pedigo
Lisa A
LA
Loebel
Nicolas G
NG
D016976:Aggregatibacter actinomycetemcomitans / Q000187:drug effects / Q000528:radiation effects; D018441:Biofilms; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D016967:Fusobacterium nucleatum / Q000187:drug effects / Q000528:radiation effects; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000528:radiation effects*; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000532:radiotherapy; D010778:Photochemotherapy; D010933:Plankton / Q000528:radiation effects; D016966:Porphyromonas gingivalis / Q000187:drug effects / Q000528:radiation effects; D013696:Temperature