Title: 0169 - Impact of Streptococcus mutans Strain-to-Strain Interactions in Biofilm Virulence Factors


Stephanie Momeni (Presenter)
University of Alabama at Birmingham

Jessica Scoffield, University of Alabama at Birmingham
Tariq Ghazal, University of Alabama at Birmingham
Noel Childers, University of Alabama at Birmingham
Hui Wu, University of Alabama at Birmingham


Objectives: Studies have reported that children with multiple strain types of S. mutans, a primary cariogenic organism, typically have higher caries scores. The purpose of this study was to determine if the presence of multiple strains of S. mutans leads to an increase in virulence traits using biofilm assays.

Methods: A patient-based model was used to select S. mutans strains previously genotyped by rep-PCR. For each profile, a caries-active child with 2 or 4 (n = 5 each) genotypes was selected. Overnight cultures were grown in Todd Hewitt Broth (THB), diluted 1:10 and grown to OD600 = 0.5. Strains were grown either individually or as a mix. The mix was generated using equal volumes of individual genotypes at same OD. Strains were diluted 1:1,000 in THB supplemented with 1% sucrose. Biofilm assays were performed in triplicate to assess biomass (0.1% Crystal Violet), glycogen (fresh 0.2% iodine solution), and pH (pHRodo, Cascade blue probes). Student’s T-test was used to determine significance.

Results: Growth rates varied considerably between strains. Mean mix biofilm biomass typically was an average of the single strains and was significantly higher for 1 profile (p = 0.008). Mean glycogen was higher for the mix in 8/10 profiles (1 profile significant, p = 0.014). Although the same volume and OD was used in the mix, the overall mean pH of mixes was significantly lower than for single strains (p = 0.045) and overall mean cell density of mixes was significantly higher (p < 0.001).

Conclusions: Mixes of S. mutans strains resulted in lower overall mean pH and higher mean cell densities than individual strains indicating that presence of multiple strains may result in increased caries risk. Multiple strains had little impact on biofilm mass or glycogen capacity. Further study is needed to determine if strain types are equally represented in the biofilm mix.

Student Presenter

This abstract is based on research that was funded entirely or partially by an outside source:
NIDCR R01DE022350 and NIDCR T-90 DE022736

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE

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