Streptococcus mutans:tooth decay, caries, plaque

By:Goua Vang

Outline

• General information about S. mutans • Biofilm • How biofilm form? • S. mutans adhere • Acid production • Affect on tooth • Prevention • Conclusion

General information

• S. mutans appear in the mouth after teeth have erupted as they need solid surfaces to colonize

• establishment is slow the first two years

• species most commonly isolated from dental plaque in humans is S. mutans

General information

• produce extracellular glucans and adhere to the tooth surfaces

• S. mutans have been found in the mouth of all populations sampled all over the world

• Usually, serotype c (Streptococcus mutans) is the dominating serotype

• One person can have several serotypes

General information

• Dental caries is a disease • microbial fermentation of dietary

carbohydrates leads to localized demineralization and destruction of the teeth

• prevalence of caries is highest on the occlusal surfaces of first and second molars, and lowest on the lingual surfaces of mandibular teeth

Biofilm

• What is a biofim?

-biofilm is a complex aggregation of microorganisms growing on a solid substrate

• characterized by structural heterogeneity, genetic diversity, complex community interactions, and an extracellular matrix of polymeric substances.

• consist of many species of bacteria living within a matrix

Biofilm

• Formation of a biofilm begins with the attachment of free-floating microorganisms to a surface

• Are usually found on solid substrates submerged in or exposed to some aqueous solution

How biofilm form?

• When tooth first erupt

-glycoproteins (pellicle) from saliva are absorpted onto the tooth surfaces

• Bacteria adhere to the pellicle, and the pellicle coats the enamal

S. mutans adhere

• The enzyme Glucosyltransferases (GTF) -synthesis of water-soluble and

insoluble glucose polymers (glucans) from sucrose

three GTFs types -GtfB, GtfC –synthesize primarily

insoluble glucan -GtfD –synthesize exclusively water-

soluble glucan

S. mutans adhere

• GtfB and GtfC are more important than GtfD for attachment

• All three is required for maximal cariogenesis

• GTFs domain

-A carboxyl-terminal region composed of multiple, homologous direct repeat segments

+constitutes the glucan-binding domain (GBD)

S. mutans adhere

S. mutans adhere

• GBD

-essential for glucan synthesis but not for sucrase activity

• N-terminal two-third of the GTFs

-is the sucrose-binding domain

+where sucrose are hydrolysis

S. mutans adhere

• SpaP

-major surface antigen that play an important role in saliva-mediated aggregation and adherence

Acid production

Acid production

• What does acid production do?

-lower the pH

-over time drop in pH lead to tooth demineralization and the development of caries

-lower the pH to 3.5

Acid production

• How does S. mutans survive?

-increase in activity and amounts of F1F0 ATPase and a low pH inducible DNA repair system

-shift in total membrane fatty acid composition • Low pH

-higher proportion of long-chained, monounsaturated fatty acids as compare to pH 7

Acid production

• Increase in pH -68% of membrane consisted of C14:0

plus C16:0

• Decrease in pH -48% C18:1 plus C20:1

Affect on the tooth

• damages the structures tooth

-cause

+tooth decay or caivites

• Untreated can lead

-pain

-tooth loss

-infection

-death in severe case

Affect on the tooth

Affect on the tooth

Location on tooth

Prevention

• Brushing

-removal of the bacteria, disrupting the biofilm

• Fluoride

-reducing enamel solubility

-remineralization of incipient enamel

Prevention (cont)

• Sealant

-plastic materials applied to fissures as a barrier against microbial attack

Conclusion

Good oral hygiene will keep the microorganism stable, but there is a need to intervene with some cleaning and dental check up annually to prevent further infection.

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• JEAN-SAN CHIA,* CZAU-SIUNG YANG, AND JEN-YANG CHEN, “Functional Analyses of a Conserved Region inGlucosyltransferases of Streptococcus mutans.”

INFECTION AND IMMUNITY, Oct. 1998, p. 4797–4803• KURT M. SCHILLINGt AND WILLIAM H. BOWEN, “Glucans Synthesized In Situ in Experimental

Salivary PellicleFunction as Specific Binding Sites for Streptococcus mutans.” INFECTION AND IMMUNITY, Jan. 1992, p. 284-295

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