title: Bactericidal effect of malachite green and red laser on Actinobacillus actinomycetemcomitans.
abstract: The aim of this study was to investigate the ability of malachite green (MG) combined with a low-power red laser to kill Actinobacillus actinomycetemcomitans and to investigate MG photodegradation after photodynamic therapy (PDT) by optical absorption spectroscopy. The etiology of periodontal disease is that microorganisms form a bacterial biofilm on the surface of the teeth. It is an infectious disease and A. actinomycetemcomitans is considered an important agent in biofilm ecology. Instead of using antibiotics, PDT is an alternative approach to eradicate bacteria. Cultures of A. actinomycetemcomitans were exposed to a 30 mW diode red laser, in the presence or absence of MG. A group of cultures was treated in dark conditions in the presence of MG (0.01% w/v) for 5 min. In the presence of MG, two exposure times for laser irradiation were used: t=3 min (energy dose=5.4 J/cm(2)), and t=5 min (energy dose=9 J/cm(2)). The samples were diluted and bacterial colonies were counted and converted into colony forming units. Absorption spectra of the bacterial suspensions, MG, MG-stained bacterial suspensions, and photosensitized bacterial suspensions were obtained. A. actinomycetemcomitans can be photoinactivated by a red laser in the presence of MG. Significant differences were observed between the two energy doses used (p<0.05). Red laser alone and MG alone were not able to kill bacteria. Optical absorption showed that MG is photobleached after irradiation. These results indicate that A. actinomycetemcomitans can be photosensitized by red laser combined with MG and that the dye is photodegraded following irradiation.
authors.affiliation: Center for Lasers and Applications, IPEN-CNEN/SP, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo SP 05508-000, Brazil. pratesra@yahoo.com.br
authors.forename: Renato Araújo
authors.initials: RA
authors.lastname: Prates
authors.forename: Aécio Massayoshi
authors.initials: AM
authors.lastname: Yamada
authors.forename: Luis Cláudio
authors.initials: LC
authors.lastname: Suzuki
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Eiko Hashimoto
authors.forename: Silvana
authors.initials: S
authors.lastname: Cai
authors.forename: Sheila
authors.initials: S
authors.lastname: Gouw-Soares
authors.forename: Laércio
authors.initials: L
authors.lastname: Gomes
authors.forename: Martha Simões
authors.initials: MS
authors.lastname: Ribeiro
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000187:drug effects* / Q000528:radiation effects; D001431:Bacteriological Techniques; D004355:Drug Stability; D006801:Humans; D007834:Lasers; D010510:Periodontal Diseases / Q000209:etiology / Q000382:microbiology / Q000628:therapy; D010778:Photochemotherapy / Q000379:methods*; D012394:Rosaniline Dyes / Q000494:pharmacology* / Q000528:radiation effects / Q000627:therapeutic use
chemical_list: D012394:Rosaniline Dyes; C005095:malachite green