Prevention of Bacterial Adhesion by Bioactive Milk Proteins
Objectives: Several bioactive milk proteins, including osteopontin, different members of the casein family, α-lactalbumin and β-lactoglobulin have been shown to hamper bacterial adhesion to saliva-coated surfaces and hence delay dental biofilm formation.
The objective of the present work was to compare the effect of osteopontin, α-lactalbumin, β-lactoglobulin, αs1-casein, β-casein, κ-casein and skim milk protein on bacterial adhesion under shear-controlled dynamic conditions.
Methods: Overnight cultures of Streptococcus mitis, Actinomyces naeslundii or Lactobacillus paracasei subsp. paracasei were mixed with sterilized salivary solution, and the purified and pasteurized proteins were added to a final concentration of 50 µM. PBS was used as the negative control. Bacterial inocula were then flushed through salivary-coated microfluidic flow chambers at a constant rate of 10 µL/h (0.1 dyn/cm2) for one h. Non-adherent bacteria were removed by PBS flow, and the amount of attached cells was quantified by bright field microscopy and subsequent digital image analysis. For each strain and protein, experiments were carried out in biological triplicates. Bonferroni adjusted t-tests were performed to assess statistical significance.
Results: In the presence of osteopontin, significantly lower amounts of adhering cells were observed for all employed strains (S. mitis: 86% reduction, p=0.043; A. naeslundii: 65% reduction, p=0.039; L. paracasei: 62% reduction, p=0.016). β-casein significantly reduced the adhesion of S. mitis (75% reduction, p=0.029) and A. naeslundii (55% reduction, p=0.026). For L. paracasei, the observed reduction did not reach the level of statistical significance (72% reduction, p=0.068). Likewise, αs1-casein, β-lactoglobulin and especially skim milk protein decreased the amount of adhering cells, but the observed reductions were not significant after Bonferroni correction. Lower or no effects were seen for α-lactalbumin and κ-casein.
Conclusions: Bioactive milk proteins, in particular osteopontin and β-casein, have the potential to delay dental biofilm formation and thus contribute to caries control.