Effect of Isolated Specific Lytic Phage against Growth and Biofilm Inhibition of Streptococcus mutans and Streptococcus sanguinis Isolated from Decayed Dental Plaque

Despite advances in oral health and dental industry, tooth decay remains one of the most common oral diseases. One of the new methods to combat dental plaque, which is the main cause of caries, is using specific lytic bacteriophage. This study aimed to investigate the effect of isolated specific lytic phage against growth and biofilm inhibition of Streptococcus mutans and Streptococcus sanguinis isolated from decayed dental plaque samples.

In this descriptive cross-sectional study, dental plaque samples were cultured in MSA-specific medium to isolate S. mutans and S. sanguinis. Suspicious isolates were examined by biochemical tests and finally confirmed molecularly by PCR. The ability to form biofilm was measured by crystal violet colorimetry on a microtiter plate. Lytic bacteriophage was isolated from urban raw sewage using double layer agar method and phage morphology was examined by TEM electron microscopy. The effect of lytic phage on the growth of S. mutans and S. sanguinis was measured by agar spot and well diffusion and its inhibition effect on biofilm was assayed by microtiter plate method.

Out of 150 plaque samples, S. mutans and S. sanguinis strains were isolated from 65 (43.33%) and 40 (26.67%) samples, respectively. S. mutans isolates showed stronger biofilm formation (OD= 0.43). The results of TEM showed lytic bacteriophage belonging to Siphoviridae family with a good inhibitory effect on the growth of S. mutans and S. sanguinis that was able to inhibit biofilm formation up to 96%.

Due to the small size of the phage particles that can have good penetration power to enter the biofilm layers, it can be concluded that the phage has the ability to fight dental plaque.