Abstract
ABSTRACTSealed cariogenic bacteria are deprived from dietary carbohydrate, but could be provided with nutrients by pulpal fluids, with adaptive strain-specific activities being possible. We investigated survival and metabolic activity of the cariogenic bacteria Streptococcus sobrinus, Actinomyces naeslundii and Lactobacillus rhamnosus in different carbohydrate-limited media without carbon source (CLM), or containing glucose (CLM-G), albumin (CLM-A), or α1-acid glycoprotein (CLM-AGP) in vitro. Bacterial metabolite concentrations (lactate, pyruvate, oxaloacetate, citrate, acetate, formate, ethanol, acetoin) after 20 and 4 hours incubation, and bacterial numbers (CFU) after 24 hours incubation were analyzed using multivariate-analysis-of-variance (MANOVA). The medium (p = 0.02/MANOVA), strain and incubation-time (both p < 0.001) had significant impact on metabolite concentrations. Bacteria secreted mainly lactate (80.3 µg/106 bacteria S. sobrinus) and acetate (54.5 µg/106 bacteria A. naeslundii). Nearly all metabolites were produced in higher concentrations in S. sobrinus than in A. naeslundii or L. rhamnosus (p < 0.05/HSD). Metabolite concentration was significantly higher in CLM-G than in other media for most metabolites (p < 0.05). L. rhamnosus showed significantly lower survival than S. sobrinus and A. naeslundii (p < 0.05/HSD) regardless of the media, while S. sobrinus and A. naeslundii showed medium-specific survival. Survival of carbon starvation was strain- and medium-specific. Sustained organic acid production was found for all strains and media.
Highlights
Bacteria are the prime etiological agent in development and progression of dental caries, which is why caries management has long focused on controlling cariogenic bacteria
Most metabolites were produced in higher concentrations in S. sobrinus than in A. naeslundii or L. rhamnosus (p < 0.05/honestly significant difference test (HSD))
The metabolic analyses of the strains S. sobrinus, A. naeslundii and L. rhamnosus grown in carbohydrate-limited media (CLM), CLM-G, CLM-A and CLM-AGP displayed a distinct profile of extracellular concentration changes of different metabolic products for each bacterial strain (Table 1)
Summary
Bacteria are the prime etiological agent in development and progression of dental caries, which is why caries management has long focused on controlling cariogenic bacteria. One such therapy for controlling the activity of cariogenic bacteria is sealing them, with sealed bacteria being cut off from the supply with dietary carbohydrates, impacting on bacterial survival, metabolic activity, and resulting in clinical lesion arrest [1,2]. In deeper lesions close to the dental pulp, bacteria could be provided with nutrients by the pulpal fluid over the dentinal tubules. This fluid consists of different compounds like glucose, glycoproteins and proteins [6,7], which can function as carbon sources
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