Microbiology of Caries I

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Microbiology of Caries I

• Oral Biology 520
• April 15, 2008
• Sun Oh Chung

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Caries is
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Topics

• Tooth Structure
• Historical Perspectives
• Biofilm/Dental Plaque
• Enamel Caries
• Streptococcus
• Major Virulence Factors
• Lactobacillus
• Actinomyces
• Effect of Quorum Sensing

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Caries
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Tooth Structure
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Enamel
Dentin
Pulp
Cementum
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Historical Perspectives on Caries
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Historical Perspectives on Caries
17th 18th 19th
20th 21st
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Historical Perspectives on Caries

• 1924 Clark recovered Gram-positive cells
• 1960 Fitzgerald Keyes found caries-conducive
  streptococci to be Streptococcus mutans

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Is caries genetically or infectiously determined?
F1
F1
sucrose sucrose caries
caries
F2
F2
F3
F3
penicillin
caries
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Caries is

• Infectious bacterial
• Etiologic agents?

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Biofilm
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Dental Plaque
(Kolenbrander, Microbiol Mol Biol Rev, 2002)
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Healthy Sites vs. Diseased Sites
(Marsh, Microbiology, 2003)
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Protective Factors
Pathological Factors
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Abundance of Bacterial Species in Caries Patients
Actinomyces sp. S. mutans Lactobacillus
sp. Fusobacterium sp. Porphyromonas
sp. Haemophilus sp. Bacteroides sp.
Gemella morbillorum Eubacterium sp. Streptococcus
sp. Streptococcus cristatus Streptococcus group
H6 Gemella haemolysans S. parasanguinis
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Under-abundant species In caries-active
Over-abundant species In caries-active
(Adapted from Corby et al., J Clin Microbiol,
2005)
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Type of Caries
Enamel
Pit fissure
Dentin, Root
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Enamel Caries
(www.db.od.mah.se Malmö University, Sweden)
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Streptococcal Species Implicated in Enamel Caries

• Mutans Streptococci
• S. mutans
• S. sobrinus
• Viridans Streptococci
• S. mitis
• S. salivarius
• S. sanguinis

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Streptococcal Species Implicated in Enamel Caries

• Mutans Streptococci
• S. mutans
• S. sobrinus
• Viridans Streptococci
• S. mitis
• S. salivarius
• S. sanguinis

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Major Virulence Factors of S. mutans

• Adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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Major Virulence Factors of S. mutans

• Adherence to teeth
• Surface proteins for adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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Initial Attachment
Pellicle glycoprotein
PBP
S. mutans
PBP Pellicle Binding Protein
(Adapted from Slots Taubman, 1992)
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Major Virulence Factors of S. mutans

• Adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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Enzymes Secreted for Glucan Synthesis

• Glucosyltransferases
• Fructosyltransferase Fructanase

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Glucosyltransferases

• GtfB, GtfC, GtfD
• Their absence associated with extremely
  diminished capacity to induce caries (Kuramitsu,
  Crit Rev Oral Biol Med, 1993)
• GtfB levels in saliva correlated with DMFS
  (Vacca-Smith et al., Caries Res, 2007)
• Potential for chair-side tests?

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GTF Binding Glucans
Sucrose
Glucose
Fructose

GTF-S
GTF-I
Glucans
Insoluble form (a-1,3-linked) Mutan
polymerized by GtfB Soluble form (a-1,6-linked)
Dextran polymerized by GtfD GtfC responsible
for a mixture of a-1,3 a-1,6
(Adapted from Slots Taubman, 1992)
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Aggregation
Pellicle Glycoprotein
Glucan Binding Protein
S. mutans
S. mutans
S. mutans
(Adapted from Slots Taubman, 1992)
Glucans
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Decreased Adhesion of S. mutans Strains Lacking
Glucan Binding Protein
WT GBP Mutants
(Matsumoto et al., Oral Microbiol Immunol, 2007)
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Decreased GTF Activity of S. mutans Strains
Lacking Glucan Binding Protein
WT GBP Mutants
(Matsumoto et al., Oral Microbiol Immunol, 2007)
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Caries is

• Infectious bacterial
• Etiologic agents?
• Dependent on dietary carbohydrates

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Major Virulence Factors of S. mutans

• Adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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Fructosyltransferase (FTF) Fructanase
Sucrose
Glucose
Fructose

Fructosyltransferase
Fructan Polymers (soluble)
Fructanase
Monosaccharides
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Major Virulence Factors of S. mutans

• Adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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Sugar
Demineralization occurs
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S. mutans
Acid
S. mutans
S. mutans
(Adapted from Slots Taubman, 1992)
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Caries is

• Infectious bacterial
• Etiologic agents?
• Dependent on dietary carbohydrates
• Dependent on demineralization-remineralization
  cycle

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Major Virulence Factors of S. mutans

• Adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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Streptococcal Resistance to Acid Stress

• Arginolysis
• ATPase
• Stress-response proteins

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Arginolysis
Streptococci
ADS Urease
Ammonia ATP
Arginine Urea
ADS Arginine/Agmantine deiminase systems
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ATPase
Optimal pH S. mutans 6.0 Lactobacillus 5.0
pH
ATPase
H
H
pH 0.5 1 unit higher than extracellular
environment
pH
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ATPase
pH
Fluoride Benzoate Ketoprofen
ATPase
H
H
pH
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Stress-response Proteins
pH
DNA damage
Stress- response Proteins
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Acid Adaptation of S. mutans Biofilm vs.
Planktonic
(McNeill Hamilton, FEMS Microbiol Lett, 2003)
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Decreased Aciduricity of S. mutans Strains
Lacking Glucan Binding Protein
WT GBP Mutants
WT GBP Mutants
(Matsumoto et al., Oral Microbiol Immunol, 2007)
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Major Virulence Factors of S. mutans

• Adherence to teeth
• Glucan synthesis
• Extra storage of polysaccharides
• Acidogenicity
• Aciduricity

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S. mutans and Infective Endocarditis (IE)

• Oral streptococci - second-most involved in IE
• PAc antibody titers elevated in IE patients
• Patients with Sjögren's syndrome have repeated IE
  caused by S. mutans
• (Nomura et al., J Med Microbiol, 2007)

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S. mutans and Infective Endocarditis (IE)

• Same isolates from the oral cavity and the
  infected heart valve of the same patient?
• Different GTF types
• Adhesion rates of the isolates from heart valve
  significantly lower
• (Nomura et al., J Med Microbiol, 2006)

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Lactobacillus
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Lactobacillus
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Lactobacillus the Good

• Part of the normal flora of almost all mucosal
  membranes
• Ferments lactose and fructose
• Secretes lactase
• Degrade sugars
• Reduce the number of pathogenic microorganisms
• Helps maintain proper pH balance

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Lactobacillus the Bad

• Produces lactic acid
• Aciduric - ATPase
• Not able to form caries by itself
• Colonizes in the biofilms with the help of S.
  mutans

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Actinomyces
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Genotypic Diversity of Actinomyces
(Paddick et al., Appl Environ Microbiol, 2003)
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Genotypic Diversity of Actinomyces

• Certain genotypes more prevalent in caries-active
  individuals
• Effect of the environment
• acidic pH a factor?

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vs.
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Quorum Sensing
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com genes of S. mutans

• Initiates biofilm formation of S. mutans
• Optimal when the cells are in actively growing
  biofilm
• Mutations lead to
• abnormal biofilm formation
• changes in membrane integrity and acid tolerance

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Quorum-sensing important in acid adaptation
(Li et al., J Bacteriol, 2001)