Comparative study of methylene blue and erythrosine dyes employed in photodynamic therapy for inactivation of planktonic and biofilm-cultivated Aggregatibacter actinomycetemcomitans.

AIM: The proposal of this work was to test the efficacy of photodynamic therapy (PDT) by using methylene blue (MB) and erythrosine (ERY) to inactivate Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), the main pathogen in aggressive periodontitis. METHODS: A. actinomycetemcomitans was cultivated in planktonic cultures and biofilm by using Tryptic Soy Broth medium. The sensibility (dark toxicity) to MB and ERY was determined, and its ideal concentration for PDT protocols was established. An odontologic resin photopolymerizer was used as the light source. The bacterial viability was determined by CFU (planktonic cultures) and microscopic observation (biofilms). RESULTS: The results show that ERY is more efficient at killing bacterial cells of A. actinomycetemcomitans in planktonic (75%) and biofilm (77%) culture compared with MB (50% and 54%, respectively). CONCLUSION: PDT using MB or ERY as a photosensitizing agent and odontologic resin photopolymerizer as a light source could be an efficient option for pocket decontamination in aggressive periodontal disease.

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. MATERIALS AND 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. CONCLUSION: 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.

Reversion by calcium of a yeast-like development to the original filamentous form, of the 10V10 5-fluorocytosine-sensitive mutant of Aspergillus niger

Alguns fungos filamentosos apresentam o fenômeno de dimorfismo, sendo que as alteracões da estrutura morfológica podem induzir alteracões metabólicas. A linhagem de Aspergillus niger 10v10, produtora de ácido cítrico foi submetida à acão mutagênica da radiacão ultravioleta selecionando mutantes sensíveis ou resistentes ao antifúngico 5-fluorocitosina (5-FC). Os mutantes selecionados como sensíveis a 5-FC apresentaram uma alteracão morfológica com desenvolvimento leveduriforme. Nestes mutantes foram avaliados o efeito da alteracão de pH, a adicão de sais (KH2PO4, NH4NO3, MgSO4e MnCl2), a presenca de estabilizadores osmóticos, cloreto de cálcio, e o seu efeito sobre a reversão morfológica e a producão de ácido. A reversão morfológica para a forma filamentosa ocorreu apenas na presenca de CaCl2 (500mM) para as linhagens mutantes 1 e 2, enquanto que a producão de ácido ocorreu nas duas formas, leveduriforme e filamentosa.