Photodynamic therapy in planktonic and biofilm cultures of Aggregatibacter actinomycetemcomitans.
OBJECTIVE
To evaluate the inactivation of Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), responsible for causing aggressive periodontitis, using photodynamic therapy (PDT) by rose bengal (RB) as a model of a reactive oxygen species (ROS) generator, in planktonic and biofilm cultures.


METHODS
A. actinomycetemcomitans was grown in planktonic and biofilm cultures using tryptic soy broth medium. The sensibility (dark toxicity) to RB was determined, and its ideal concentration for PDT was established. Concentrations in the range from 0.01 to 50.0 micromol L(-1) RB, with different light potencies and incubation times, were used. An odontological resin photopolymerizer that emits the adequate wavelength for absorption of the RB dye was applied. Bacterial viability was determined by colony- forming units (CFU).


RESULTS
RB photosensitizer dye in concentrations up to 0.1 micromol L(-1) did not show toxicity per se toward A. actinomycetemcomitans cells. In a PDT study with photoirradiation (1 min) at 0.1 micromol L(-1), a 55% reduction of A. actinomycetemcomitans viability was obtained in planktonic cultures. Preincubation (30 min) of the bacteria with the dye resulted in a 90% reduction of its viability. It is important to note that, for dye concentrations up to 1 micromol L(-1), in the same experimental conditions, no death effect on gingival fibroblasts was observed. The A. actinomycetemcomitans biofilm was not affected by RB or light alone. After PDT, the reduction in the biofilm (about 45%) is significantly dependant on RB concentration and irradiation time when this dye was used as a ROS generator.


CONCLUSIONS
Photodynamic therapy-generated ROS inactivates A. actinomycetemcomitans both in planktonic and biofilm cultures, even in small concentrations of the photosensitizing agent, and it does not cause damage to fibroblast cells under the same conditions.
Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil.
Rosangela de Carvalho
Rde C
Goulart
Mayte
M
Bolean
Tony de Paiva
Tde P
Paulino
Geraldo
G
Thedei
Sérgio L S
SL
Souza
Antonio Cláudio
AC
Tedesco
Pietro
P
Ciancaglini
D016976:Aggregatibacter actinomycetemcomitans / Q000528:radiation effects*; D001426:Bacterial Proteins / Q000032:analysis; D018441:Biofilms; D002478:Cells, Cultured / Q000187:drug effects / Q000528:radiation effects; D005347:Fibroblasts / Q000187:drug effects / Q000528:radiation effects; D005456:Fluorescent Dyes; D005881:Gingiva / Q000166:cytology; D050296:Microbial Viability / Q000187:drug effects*; D010518:Periodontitis / Q000382:microbiology; D010778:Photochemotherapy; D017319:Photosensitizing Agents; D010933:Plankton / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012395:Rose Bengal; D013997:Time Factors
D001426:Bacterial Proteins; D005456:Fluorescent Dyes; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D012395:Rose Bengal