Microbiology of dental caries
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MICROBIOLOGY OF DENTAL CARIES. INTRODUCTION. INFECTION: DISEASE: ASYMPTOMATIC CARRIAGE: COLONIZAION: ( NORMAL FLORA). BACETRAIL PATHOGENESIS. What is virulence? The ability of a bacterium to cause infection. Virulence factors: Two types:

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Introduction l.jpg
INTRODUCTION

  • INFECTION:

  • DISEASE:

  • ASYMPTOMATIC CARRIAGE:

  • COLONIZAION: ( NORMAL FLORA)


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BACETRAIL PATHOGENESIS

  • What is virulence?

    The ability of a bacterium to cause infection.

  • Virulence factors: Two types:

    • Those that promote bacterial colonization and invasion of the host tissue

    • Those that cause damage of the host tissue.


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Research in the past four decades have accumulated information which led to identification of possible pathogens of human dental caries.

Q. How a cause and effect relationship is established between bacterium and the disease?

A. Koch’s Postulate (1800s).


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KOCH’S POSTULATES information which led to identification of possible pathogens of human dental caries.

  • The bacterium should be found in people with the disease

  • The bacterium should be isolated from the lesions of infected person

  • Pure culture, inoculated into a susceptible individuals or animals should produce the disease

  • Same bacterium should be re-isolated from intentionally infected animals or humans.


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LIMITATIONS OF KOCH’S POSTULATES information which led to identification of possible pathogens of human dental caries.

  • Virulence is within the bacterium and is independent of the host

  • Isolation and growth of bacterium is necessary: Yet, some pathogens not yet cultured

  • Nos. 2 & 4: assume that all members of the same species are virulent

  • No. 3: Ethics with human subjects, Yet some pathogens from humans can not cause the same effect in animals.


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WHAT IS THE ALTERNATIVE? information which led to identification of possible pathogens of human dental caries.

MOLECULAR POSTULTES

  • Gene should be found in the bacterial strain.

  • Disturbing the virulent gene should reduce its virulence.

  • Bacterial virulent gene should be expressed in the animal or human at sometime during the infectious process

  • Abs to gene product should be protective or should elicit protective immunity (cell-mediated).


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Q. Why Did it Take Long Time for Caries Microbiology? information which led to identification of possible pathogens of human dental caries.

  • Complex ecology of the oral cavity.

    • 300 – 400 species are indigenous oral flora.

    • History:

      • Miller (1880): Little knowledge about which bacteria.

      • Clarke (1924): First who associate bacteria with dental caries

        • First to isolate MS from human dental caries

        • First to produce caries in extracted teeth.

      • Orland (1955): Used animals to induce dental caries using MS.


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DENTAL CARIES MICROBIOLOGY RESEARCH information which led to identification of possible pathogens of human dental caries.

  • 1960s : germ-free animals

  • 1960s and 70s: importance of glucan (glucanase):

    • Clinical trials using glucan hydrolyase rinses

    • Glucan is plaque enhancer

    • Problem with isolation: Number, media ….etc.

    • Specific plaque theory

  • MS identified as an associated bacteria with caries.


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MUTANS STRPETOCOCCI (MS) information which led to identification of possible pathogens of human dental caries.

  • TYPES: (Coykendall, 1989)

    • S. anginosus: important in purulent infections

    • S. bovis: found in patients with colon cancer

    • S. mitis: similar to sanguis but doesn’t ferment any sugar

    • S. mutans : seven species

    • S. salivarius: in saliva, rare in infections

    • S. sanguis: causes endocarditis

    • S. vestbularis: new species from oral cavity.


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STREPTOCOCCUS MUTANS information which led to identification of possible pathogens of human dental caries.


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SUMMARY information which led to identification of possible pathogens of human dental caries.


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WHY information which led to identification of possible pathogens of human dental caries.S. mutans SUCCEED?

  • Three factors:

    • Ability to adhere to other bacteria and tooth surface

    • Ability to rapidly metabolize nutrients (CHO)

    • Ability to tolerate acidic environment.


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ADHERENCE OF information which led to identification of possible pathogens of human dental caries.S. mutans

  • Saliva:

    • Lysozyme

    • IgA: (IgA protease), (IgA deficiency)

  • Bacterial proteins:

    • Ag I/II family: Adhere to saliva proteins

    • Adhesin

    • Fimbrial adhesion: Adhere to saliva pellicle

    • glucan binding (GBP)


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CHO METABOLISM BY information which led to identification of possible pathogens of human dental caries.S.mutans

  • CHO must be transported across the membrane (Sugars must be phosphorylated):

    • Multiple Sugar Metabolism (MSM) System:

    • Transport via the Phosphoenolpyruvate (PEP):

    • Sugar Phosphotransferase System (PTS):


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CHO Metabolism information which led to identification of possible pathogens of human dental caries.

PEP + CHO PTS Pyruvate +P-CHO

  • S.mutans enolase: Fluoride inhibits it.

  • S.mutans store polysaccharides .. Why?


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S. mutans information which led to identification of possible pathogens of human dental caries. ACID TOLERANCE

  • Through cell membrane, extrusion of protons:

    • Membrane ATPase hydrolyze ATP molecules

    • Hydrolysis of one ATP, results in extrusion of three protons

    • This results in elevation of cytoplasmic pH.

    • When pH decreases, ATPase activity increases 4-folds.


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COLONIZATION OF information which led to identification of possible pathogens of human dental caries.S. mutans

  • Based on ability of S. mutans to synthesize insoluble glucan.

  • S. mutans have 3 genes:

    • gtfB encodes GTF-I enzyme: insoluble glucan

    • gtfC encodes GTF-SI enzyme: insoluble glucan

    • gtfD encodes GTF-S enzyme: soluble glucan


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RESEARCH USING GTFs information which led to identification of possible pathogens of human dental caries.

  • Purified S.mutans GTFs were used for caries immunization in rodents.

    (Smith et al., 1979).

  • Implantation of S. mutans defective in IS glucan synthesis into rats resulted in reduced smooth surface caries induction.

    (Munro et al., 1991).


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Strain Gtase Adherence% information which led to identification of possible pathogens of human dental caries.

MT8148 I,SI/S 72.8  2.6

B29 /SI/S 16.3  1.0

B29 I/SI/S 46.9  5.9

B58 I/ /S 9.6  1.0

B58 I/SI/S 69.9  1.8

B32 / /S 1.4  0.4

(Fujiwara et al., 1996)


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SUMMARY information which led to identification of possible pathogens of human dental caries.


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ACQUISITION OF information which led to identification of possible pathogens of human dental caries.S. mutans

  • Sterile mouth at birth

  • S. sanguis and S. mutans colonize teeth

  • Number of bacteria increases in the presence of:

    • Sucrose

    • Caries

    • Teeth


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ACQUISITION OF information which led to identification of possible pathogens of human dental caries.S. mutans

MS

26

Birth

5 Year

First Tooth 19 33

6.8 +/- 1.4 mo.

N=38

Caufield et al., J Dent Res. 72:37-45, 1993.


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ACQUISITION OF information which led to identification of possible pathogens of human dental caries.S. mutans

  • Important facts:

    • Difficult to change S. mutans strain(s)

    • High number of S.mutans strains and isolates.

    • One (or more) strain (isolates) is/are present in the mouth.


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GENETIC VARIATIONS information which led to identification of possible pathogens of human dental caries.

OF S.mutans


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TRANSMISSION OF CARIOGENIC FLORA information which led to identification of possible pathogens of human dental caries.

  • Mothers to children:

    • DNA technique

    • Method of transmission

  • Spouses:

    • Different bacteria studied

  • Replacement Therapy


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IF WE UNDERSTAND THE DENTAL CARIES information which led to identification of possible pathogens of human dental caries.

MICROBIOLOGY WELL..

WE WILL TREAT PATIENTS

DIFFERENTLY !!!!

HOW?????????????????????????????


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