Faculty Publications


Probiotic Lactobacillus sp. inhibit growth, biofilm formation and gene expression of caries-inducing Streptococcus mutans

SelectedWorks Author Profiles:

Hossam Ashour

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Streptococcus mutans contributes significantly to dental caries, which

arises from homoeostasic imbalance between host and microbiota. We

hypothesized that Lactobacillus sp. inhibits growth, biofilm formation

and gene expression of Streptococcus mutans. Antibacterial (agar

diffusion method) and antibiofilm (crystal violet assay) characteristics

of probiotic Lactobacillus sp. against Streptococcus mutans (ATCC 25175)

were evaluated. We investigated whether Lactobacillus casei (ATCC 393),

Lactobacillus reuteri (ATCC 23272), Lactobacillus plantarum (ATCC 14917)

or Lactobacillus salivarius (ATCC 11741) inhibit expression of

Streptococcus mutans genes involved in biofilm formation, quorum sensing

or stress survival using quantitative real-time polymerase chain

reaction (qPCR). Growth changes (OD600) in the presence of

pH-neutralized, catalase-treated or trypsin-treated Lactobacillus sp.

supernatants were assessed to identify roles of organic acids, peroxides

and bacteriocin. Susceptibility testing indicated antibacterial

(pH-dependent) and antibiofilm activities of Lactobacillus sp. against

Streptococcus mutans. Scanning electron microscopy revealed reduction in

microcolony formation and exopolysaccharide structural changes. Of the

oral normal flora, L.salivarius exhibited the highest antibiofilm and

peroxide-dependent antimicrobial activities. All biofilm-forming cells

treated with Lactobacillus sp. supernatants showed reduced expression of

genes involved in exopolysaccharide production, acid tolerance and

quorum sensing. Thus, Lactobacillus sp. can inhibit tooth decay by

limiting growth and virulence properties of Streptococcus mutans.