Evaluation of 5-Aminolevulinic acid, Methylene Blue, Toluidine Blue O Photosensitizers on Clinically Isolated Porphyromonas gingivalis and Prevotella intermedia: An in vitro Study

Abstract

Objective: To evaluate the antibacterial efficacy of 5-aminolevulinic acid (5-ALA), methylene blue (MB), and toluidine blue O (TBO) photosensitizers against clinically isolated Porphyromonas gingivalis (P. gingivalis) and Prevotella intermedia (P. intermedia).
 Methods: Patients with a periodontal pocket depth of ≥5 mm were selected for subgingival plaque sampling. Bacterial identification was carried out using colony morphology, gram staining and then validated using the PCR technique. The photosensitizers tested were 5-ALA, MB, and TBO. The antibacterial test was performed using an agar well, and disk diffusion methods and double-fold serial dilution was used for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). 
 Results: Glossy, smooth, and looked grey, light brown, or black-pigmented colonies of P. intermedia on Columbia agar plates were confirmed by gram staining and PCR tests. Contrary to MB and TBO, 5-ALA photosensitizers didn’t have antibacterial efficacy against P. gingivalis and P. intermedia. The antibacterial test showed an increased inhibition zone with increasing the photosensitizers’ concentration. The greatest inhibition zones were at 10mg/ml concentration for both MB and TBO. The MIC for MB was 2 mg/ml, and 1mg/ml, while for TBO, it was 1mg/ml and 0.5mg/ml for P. gingivalis and P. intermedia, respectively. 
 Conclusions: MB and TBO have antibacterial properties against P. gingivalis and P. intermedia, and their efficacy increase with increasing concentration. TBO is more effective when compared to MB. Furthermore, P. intermedia is more sensitive to photoactivation in comparison to P. gingivalis.