Isolation of the Bacteriophages Inhibiting the Expression of the Genes Involved in Biofilm Formation by Streptococcus mutans

Background: The potential of Streptococcus mutans for biofilm formation makes it one of the main organisms causing dental caries. Various preventive strategies have been applied to reduce tooth decay. Objectives: In the current study, we aimed to isolate S. mutans bacteriophages from sewage and to investigate their effects on the expression of the genes involved in bacterial biofilm formation in dental caries. Methods: Eighty-one dental plaque samples were collected. Then to isolate and identify S. mutans, bacterial culture media and molecular tests were used. Moreover, the biofilm formation capability of the isolated S. mutans was determined. Also, lytic bacteriophages were isolated from raw urban sewage, and phage morphology was determined by transmission electron microscopy (TEM). Real-time PCR was used to assess the effects of the isolated bacteriophages on the expression of the genes involved in biofilm formation. Results: Overall, 32 (39.5%) samples were positive for the presence of S. mutans. All of the isolates contained the gtfD gene. The frequencies of other genes were as follows: gtfB (17, 53.12%), gtfC (19, 53.37%), SpaP (13, 40.62%), and luxS (23, 17.87%). The isolated S. mutans bacteria presented different ranges of biofilm formation ability. Based on TEM results, two sewage-isolated bacteriophages, belonging to Siphoviridae and Tectiviridae families, were able to prevent biofilm formation up to 97%. Conclusions: Our findings indicate that phage therapy can be an optional way for controlling biofilm development and reducing the colonization of teeth surface by S. mutans.