Cariogenic bacteria growth trend in the presence of sucrose substitutes

Abstract

Objectives: To compare the growth trend of cariogenic bacteria in the presence of different sucrose substitutes. Methods: Bacterial suspensions of four cariogenic species, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus and Lactobacillus rhamnosus, were adjusted to a cell density of McFarland 4 and mixed equally. A 100 μl mixed bacterial suspension was placed in each of 18 wells of a 96-well microplate. The wells were randomly divided into 6 groups and 100 μl of one of the following mediums was added to each well of the same group: BHI broth containing 5% isomaltulose, 5% D-tagatose, 1% sucralose, 1% stevioside, 5% sucrose (positive control) and pure BHI broth (negative control). The microplate was measured in a microplate reader machine for 48-hour optical density (OD) values at a wavelength of 660 nm. The growth trend of the mixed bacteria in each medium group was derived from the mean OD value of the three wells in the same group. Results: In the first 8 hours, OD values of all groups increased rapidly. Afterwards, D-tagatose and sucrose groups continued this trend while the other four groups began to go up more gradually. The OD values of D-tagatose and sucrose started to level off after 10-16 hours. After 48 hours, the OD values of the different groups were 0.847 for D-tagatose, 0.807 for sucrose, 0.579 for isomaltulose, 0.512 for BHI, 0.443 for sucralose and 0.433 for stevioside. The bacterial growth trend in the presence of D-tagatose resembled that of sucrose. The difference in OD values between stevioside and sucralose groups were very small (p>0.05) and both of them were lower than that of BHI group (p<0.001). Conclusions: Growth of cariogenic bacteria in the presence of D-tagatose is similar to that of sucrose while these bacteria do not grow very well in the presence of stevioside or sucralose.