Analysis of probiotic antimicrobial activity and its adherence to orthodontic brackets: in vitro study

Abstract Introduction The presence of a fixed orthodontic appliance makes cleaning difficult and enhances the accumulation of bacterial biofilm on dental surfaces. It is the desire of researchers worldwide. Objective To verify the bacteriotherapeutic action of dairy products containing or not probiotics under Streptococcus mutans (SM) (ATCC 25175) and S salivarius (SS) (ATCC 7073) pools, as well as their adhesion to the surface of orthodontic brackets. Material and method Pool of SM and SS ATCC strains was formed and plated on a petri dish containing brain heart infusion agar (BHI) culture medium. After formation of the medium a hole was made in the center of the plate followed by filling with 150 µL of the products to be tested, forming the following groups: GL - Bovine milk; GLP - Probiotic bovine milk; GLF - Fermented milk and GLFP - Probiotic fermented milk. Following the plates were incubated for 48h in an oven at 37°C. After that the halo formed between the product and the medium was measured with a millimeter ruler. Already in the membrane disc was formed biofilm with the same pool of strains, under membrane discs. After this the serial dilution containing the product was made according to the group: P1 (water); P2 (L); P3 (LP); P4 (LFP), followed by plating and total microorganism count. For the adhesiveness of dairy products, orthodontic brackets were submerged in each solution (GL, GLP, GLF and GLFP), which were incubated at 37°C/24h. Subsequently, each bracket was transferred to an ependorf containing sterile saline solution, which was subjected to serial dilutions, then incubated at 37°C/48h under microaerophilia for counting CFU/mL. For data analysis, the Levene, Shapiro-Wilk and Kruskal-Wallis tests were used. The adopted significance level was 5% (α=0.05). Result There was no inhibition halo formation between the products and the culture medium (p<0.05); In the membrane disc no statistical differences were observed between the groups (p=0.679); The group treated with probiotic bovine milk and probiotic fermented milk showed adherence to orthodontic brackets (p = 0.056). Conclusion The findings of the present study allow us to conclude that, in in vitro studies, it was not possible to verify bacteriotherapy from dairy products containing or not probiotics in SM and SS strains.