Evaluate the efficacy of Probiotic Lactobacilli on growth and biofilm formation in Streptococcus mutans isolated from gingivitis

Abstract

The present study aimed to assess the antibacterial effects of Probiotic Lactobacilli against Streptococcus mutans isolates. A total of 13/52 (25%) S. mutans isolates were collected from patients suffering from gingivitis, which were identified using morphological characteristics, biochemical tests and PCR technique. Micro titer plate method was used to detect the biofilm formation in tested bacterial isolates by measuring optical density (OD) using ELISA reader at a wavelength 640 nm. The results revealed that only 10/13 (77%) isolates produced the biofilm. Based on the results obtained in this study, the isolates were classified according to their ability to the biofilm formation as follows: The isolates with thick biofilm (OD = 0.300 nm), the isolates with moderate biofilm (OD 0.2-0.3 nm), the isolates with thin biofilm (OD 0.1-0.2 nm) and Non-productive isolates of biofilm (OD < 0.1 nm). On the other hand, the agar well diffusion method was used to evaluate the effectiveness of Probiotic Lactobacilli against the growth of bacterial isolates by measuring the inhibition zones around the wells containing of probiotics (50, 100 mg/ml and stock). The results indicate that inhibition zones of the tested isolates were weak at 50 mg/ml, moderate at 100 mg/ml and strong at stock solution. A modified crystal violet test in well micro-titer plates was used to detect the ability of isolates to the biofilm formation after treatment with various concentrations of Probiotic Lactobacilli by measuring optical density (OD). The results indicate a decrease in the ability of the tested isolates to the biofilm formation compared to control where the isolates treated with probiotics at 50 mg/ml formed a strong biofilm (OD 0.300-0.341 nm) and the isolates treated with probiotics at 100 mg/ml formed moderate biofilm (OD 0.209-0.263 nm), while the isolates treated with the stock solution of probiotics formed a thin biofilm (OD 0.144-0.198 nm). In conclusion, the results of the current study indicate that the Probiotic Lactobacilli have inhibitory effect on growth and biofilm formation in Streptococcus mutans isolates and the antibacterial activity of Probiotic Lactobacilli is increased with increasing concentration.