Evaluation of the effect of different infant formulas on Streptococcus mutans biofilm formation: an in-vitro study

Considering the increase in the prevalence of early childhood caries, the effect of various types of frequently consumed infant milk formulas on the development of Streptococcus mutans biofilm was examined. Three samples of cow's milk-based formula (Aptamil, Bebelac, Nan), two samples of soy-based formula (Biomil soy and Isomil soy), and three samples of formulas containing hydrolyzed proteins (Aptamil HA, Bebelac HA, Nan HA) were selected. After adding the formulas to the Streptococcus mutans (ATCC 35668) culture media, the degree of bacterial biofilm formation was explored by assessing the optical density (OD) of the Cristal Violet dye in the decolorizing solution using an ELISA reader device. The analysis of the data was conducted using independent sample T-tests, ANOVA, and subsequently Fisher's LSD test using SPSS 22 software. A statistically significant difference was observed in the average levels of biofilm formation of Streptococcus mutans for the three types of understudy formulas (P < 0.001). In the presence of cow's milk-based formulas, the mean amount of biofilm formation was significantly greater than that of the soy-based (P = 0.003) and protein hydrolysate (P < 0.0001) formulas. However, no significant statistical difference was detected between the soy-based and protein hydrolysate formulas (P = 0.42). Aptamil exhibited the highest amount of biofilm formation with a mean OD of 1.81 whereas Aptamil HA showed the lowest amount of biofilm formation (OD = 0.61). The level of biofilm formation by Streptococcus mutans when exposed to cow's milk-based formula was noted to be greater than that observed with the soy-based and protein hydrolysate formulas.