1. ADHESINS AND RECEPTORS
IN Dental Plaque
PRESENTED BY : RANEEM GAMAL
SUPERVISED BY : DR. YASMEEN FOUAD
2. OUTLINE
Introduction
Dental plaque definition
Dental plaque composition
Types of dental plaque
Mechanism of dental plaque formation
1. Formation of acquired pellicle.
2. Bacterial adherence (adhesins and receptors)
3. Formation of inter-microbial matrix
4. Bacterial colonization and plaque maturation (co-aggregation)
5. Dispersion
Innovations and future research.
3. Introduction
The classic presentation of periodontal disease is associated with
accumulation of plaque and calculus that harbors bacteria and
potent virulence factors which lead to destruction of periodontal
tissue and resorption of alveolar bone around teeth.
4. Dental Plaque
• Dental plaque is a complex microbial community (predominantly bacteria, but it may
contain yeast , protozoa and virus) found on the tooth surface, embedded in a matrix
of bacterial and salivary origin, so firmly adherent to tooth surface that they resist
wash off by salivary flow.
6. Types of Dental Plaque
Plaque is divided into 2 distinct types based on the relationship of the
plaque to the gingival margin:
• Supragingival plaque
• Subgingival plaque
7. Supragingival plaque dominant bacteria :
Facultative streptococci (90%)
Actinomyces species
Subgingival plaque dominant bacteria according to location :
1. Tooth associated gram positive rods and cocci such as;
Streptococcus mitis
Streptococcus sanguis
Actinomyces viscosus
Actinomyces naeslundii
8. 2. Tissue associated bacteria in these area are more loosely organized than the
very dense tooth associated region.
It contains gram negative rods and cocci as well as filaments, flagellated rods
and spirochetes.
Bacteria mostly predominate tissue associated flora include;
Prophyromonas gingivalis
Prevotella intermedia
Actinobacellus actinomycitimocometans
Capnocytophaga
9. The process of plaque formation can be divided into:
1. Formation of acquired pellicle.
2. Bacterial adherence
3. Formation of inter-microbial matrix
4. Bacterial colonization and plaque maturation
5. Dispersion
10.
11. 1.Formation of Acquired Pellicle
All surfaces of the oral cavity, including all tissue surfaces as well as surfaces of
teeth and fixed and removable prosthesis are covered with a glycoprotein
pellicle.
• Dental pellicle can be considered as the “skin” of the teeth. It is also called acquired
pellicle, salivary acquired pellicle, and enamel pellicle.
• They form in just few seconds after brushing the teeth. If left undisturbed will turn
into plaque which if left again will turn into caries and periodontal disease
12. • In addition to components originating from salivary glands, pellicles also contain
molecules that are not of salivary gland origin, including:
• Albumin originating from gingival crevicular fluid
• Bacterial products such as the glucosyltransferase of S. mutan
Among the salivary components that have been detected in enamel pellicle are :
• MUCINS • α-AMYLASE • S IgA • CYSTATINS • LYSOZYME. • PROLINE RICH
PROTEINS (PRPS).
13. The pellicle forms by selective adsorption of the environmental
macromolecules.
The mechanisms involved in enamel pellicle formation include
Electrostatic
Van der waal
Hydrophobic forces.
14. PROBABLE FUNCTIONS of The Acquired
Pellicle :
• Protect against acid attack (local buffering)
• Facilitate adhesion of gingiva to enamel surface
• Assist in remineralization
• Bind microorganisms
15. Initial colonization of the tooth surface:
The initial bacteria colonizing the pellicle coated tooth surface are predominantly
gram - positive facultative microorganisms such as actinomyces viscosus and
streptococcus sanguis.
The initial colonizers adhere to the pellicle through specific molecules termed
adhesins, on the bacterial surface that interact with receptors in the dental pellicle.
• They reduce oxygen tension to the low level required for growth and survival
of anaerobic secondary colonizers .
16.
17. 2.Bacterial Adherence
Plaque bacteria have developed adhesion mechanisms to colonize surfaces in the
mouth and to withstand cleansing actions, such as salivary flow.
Probably the single most important phenomenon in the development of a biofilm
is the process of microbial adhesion either to the substratum or to other adhering
cells of the same or another species.
18. Adhesins
• Adhesins are minor fimbria-associated proteins and are presented on the cell
surface at or near the tip of thin fimbrial structures extending from the cells.
• The theoretical maximum number of adhesin molecules on a cell surface is 300
and 500 molecules per cell for the 43- and 75-kDa adhesins size, respectively .
• Studies of coaggregation-mediating adhesins among the Gram-positive oral
bacteria have been limited to only a few streptococci and actinomyces.
• The adhesins of Gram-negative bacteria can be divided into two classes: fimbrial
adhesins and nonfimbrial adhesins.
19. 1.Streptococcal antigen I ⁄ II family of
proteins
• They are Polypeptides expressed by commensal oral streptococci such as S. gordonii,
S. oralis and S. sanguinis.
• High affinity binding is made by short fimbriae of P gingivalis which engage antigen
I/II adhesion on streptococci. (Jakubovics et al, 2005)
• Active immunization against Ag I/II or to block adhesins (fimbriae) with specific
inhibitors such as peptides have been recently investigated for immunization against
dental caries and PD (Younson and Kelly, 2004), (Li et al, 2009).
20. • Streptococci have the ability to coaggregate with other streptococci
( intrageneric coaggregation) , which offers an extra advantage in allowing them to
bind to the nascent monolayer of already bound streptococci . In addition,
actinomyces, which are other primary colonizers, bind to the acquired pellicle and to
the streptococci.
21.
22.
23. 2. Galactose binding adhesins
• It is an outer membrane polypeptide on F. nucleatum
• Mediates not only coaggregation with P. gingivalis, but also the attachment of F.
nucleatum to a variety of mammalian cells including human gingival and periodontal
ligament fibroblasts, macrophages, and PMNs (Weiss EI, et al. 2000)
• F. nucleatum is sometimes thought of as a bridging bacterium in plaque, adhering to
primary colonizers
24.
25. 3. Galactosyl-binding adhesins
• The increased exposure of galactosyl residues promotes the interaction of
actinomyces with this salivary molecule in the early stages of biofilm formation.
• Several mechanisms have been identified for adherence of A.actinomycetemcomitans
to epithelial cells : extracellular amorphous material, fimbriae, and extracellular
vesicles may all be involved .
• Smooth variants invade more proficiently than rough variants. Fimbriae most
probably function in adherence of rough variants, whereas non-fimbrial components
(eg. vesicles) are probably involved in adherence of smooth, highly invasive strains .
26. • Type 1 fimbriae mediate binding to saliva coated hydroxyapatite(SHA) and
specifically to salivary proline-rich proteins. Type 2 fimbriae mediate lactose-
inhibitable binding to other oral bacteria and to mammalian cells. Some
actinomyces strains bear both types of fimbriae, and others bear only type 2
27. 4.Glucan-binding proteins
• These are essentially lectins that bind glucans inside plaque matrix
• GBPs are found on the cell surface of S. mutans, and some other streptococci.
28. 5. Arginin inhibitable adhesins:
• It is a cell-surface protein of F. nucleatum
• It mediates large numbers of S. cristatus to adhere to F. nucleatum,
resulting in formations known as corncobs coaggregation (Kaplan et al,
2009).
• It enables S. cristatus to passively invade human epithelial cells (Edwards
et al. 2007)
29.
30. 6. Hemagglutinin
• It is important adhesion molecule which allows P gingivalis to adhere to gingival
tissue cells and to attach and lyse erythrocyte in order to uptake (Fe) ions as essential
nutrition
• Can bind to host proteins, such as fibronectin, fibrinogen , laminin, and collagen
type V . that have been reported to coat epithelial, endothelial, and fibroblast cells.
(TezukaA , et al.2006 , Sakai E, et al. 2007)
• Hemagglutinins are expressed on the bacterial cell surface in association either
with filamentous structures such as fimbriae (fimbrial adhesins) or with nonfimbrial
surface components (nonfimbrial adhesins) and are frequently the adhesins
through which bacteria attach to mammalian cells. (Han.1996)
31. 7.Bacterial Lipopolysaccarides
• Probably facilitates coaggregation with the diverse variety of
grampositive (Streptococcus and Actinomyces species) and
gramnegative (Haemophilus, Prevotella, and Veillonella) species
32.
33.
34.
35.
36. 1- Statherin receptors
• Porphyromonas gingivalis long fimbriae (FimA) adhere to salivary statherin in
pellicle.
• Of all human salivary proteins, statherin exhibited the strongest ability to bind to F.
nucleatum cell surface protein . (Sekine S et al. 2004, NakagakiH, et al, 2010)
Receptors
37. 2. Sialic acid binding protein receptor
• One of the components of saliva incorporated in acquired pellicle and act as a
receptor provided by the host for the early colonizers S. sanguinis and S. gordonii.
• Both organisms express specific cell surface adhesin molecules called the sialic acid–
binding protein.
• Inhibited by sialidase enzyme
38. 3.Proline-rich proteins (PRPs)
• Actinomyces naeslundii type 1 fimbriae and Porphyromonas
gingivalis long fimbriae (FimA) adhere to PRPs.
• PRPs are not only receptors for binding bacteria , they are also a ready
nutrient source for early colonizers. S. gordonii They can bind to other
host receptors or to other bacteria while degrading the PRP nutrient.(Li T
et al. 2000)
39. 4-Salivary agglutinin or glycoprotien340
• When gp340 is integrated into the acquired enamel pellicle, it was found to
promotes adhesion of streptococci binding proteins. (Loimaranta et al., 2005)
40.
41. 3.Formation of intermicrobial matrix
Organic substances formed by bacterial enzymes from sucrose, they are mainly
polysaccharides of:
• Glucans • Levans.
• The glucan is mainly dextran which is a sticky adhesive material that plays a major
role in colonization of bacteria.
• Glucan synthesis allows the bacteria to firmly attach to the tooth surface and form a
biofilm.
• Levan function as storage of polysaccharide, providing a source of fermentable
carbohydrate when hydrolyzed.
42. 4.Bacterial colonization and plaque
maturation
• Secondary colonizers are the microorganisms that do not initially colonize
clean tooth surface.
• Secondary colonizers include: Fusobacterium nucleatum, • Prevotella
intermedia, and • Capnocytophaga species.
• Interaction occurs among different gram positive species and gram
negative species.
• In the later stages of plaque formation , coaggregation between different
gram negative species predominates.
43.
44. • After one week of plaque accumulation, other gram-negative species may also be
present in plaque. These species represent what is considered to be the "tertiary
colonizers", and include:
• 1. Porphyromonas gingivalis (Pg)
• 2. Aggregatibacteractinomycetemcomitans
• 3. Campylobacter rectus
• 4. Eikenella corrodens
• 5. Spirochetes (Treponema species).
• Gram positive species use sugars as an energy source and saliva as a carbon source
• The bacteria that predominates in mature plaque are anaerobic and asaccharolytic,
and use amino acids and small peptides as energy sources
45. Colonization and adsorption to a surface are followed by the
matrix production and development of the water channels
46.
47. The initial attachment of primary colonizers to oral surfaces presents new receptors for
the subsequent adhesion of other bacteria.
The binding of bacterial cells to pre-adherent cells on a surface is important for the
recruitment of secondary colonizers to the oral biofilm. The adhesion of different
bacteria to one another in suspension is termed ‘co-aggregation’
(Cisar et al., 1979)
In many cases, co-aggregation involves the recognition of carbohydrate structures on
one organism by lectin-like protein adhesins on the compatible partner. The
identification of the key protein adhesins is still very much a work in progress.
Co-Aggregation and Co-adhesion
48. Conclusion
• Coaggregation is highly specific in that partners of one cell type may not be partners of a closely
related cell type.
• The recognition may be intrageneric, intergeneric or multigeneric in nature .
• All coaggregations occur between genetically distinct bacteria, including those that occur between
bacteria of the same genus.
• The latter intrageneric coaggregations seem to be limited to those among streptococci and a few
actinomyces; both of these groups of bacteria are initial colonizers and may use intrageneric
coaggregation as a critical function in adherence
49. • An interesting feature of the coaggregations is the bridging
between one cell type and its partners.
• One of the first examples of a coaggregation bridge was
Prevotella loescheii PK1295, which can serve as a bridge
between Streptococcus oralis and Actinomyces israelii PK14,
two gram-positive oral bacteria that are otherwise unable to
coaggregate
53. Carbohydrate receptors that mediate coaggregation have been
isolated and extensively characterized from five streptococci .
All five of the carbohydrate receptors are linear cell wall
polysaccharides, each having been removed from the cell wall
by the action of mutanolysin,
a mureinolytic enzyme.
54. Several structural features are common to these receptor
polysaccharides. All contain:
1- Galactopyranose and -galactofuranose
2- Hexasaccharides or heptasaccharides
3 - Phosphodiester linkages.
55.
56. The top four of the five polysaccharides are similar in structure and in
biological activity and will be discussed as a group.
- Two common features of these four polysaccharides are :
1) the oligosaccharide repeating units are linked by phosphodiester bonds to the
6-carbon of the nonreducing terminal sugar.
2) all contain N-acetylgalactosamine.
- The top two streptococcal polysaccharides
contain --Galfi 1-36)-f3-GalpNAc (1-*3)-a- Galp(1-*)
- The next two contain -J-GalJ(1--*6)-fr Galp( 1-i.3)-ct-GalpNAc (1-i).
They differ in the order of the two sugars near the reducing end (GalNAc-
Gal vs.
Gal-GalNAc), but the glycosidic linkages are the same.
This disaccharide region of the four oligosaccharides is considered to be the
active actinomyces-adhesin binding site. Abeygunawardana et al.
57. All four of these streptococci are partners of actinomyces and all exhibit lactose-
inhibitable coaggregalions with some of the actinomyces.
Yet the degree of coaggregation of the streptococcus-actinomyces coaggregation
varies with each streptococcus and any common- partner actinomyces.
For example,
S. sanguis C104 co-aggregates poorly with A. naeslundii T14V, whereas the other
three show strong coaggregation.
58.
59. The fifth streptococcal polysaccharide acts as a receptor for a
Gram-negative bacterium.
Of the five streptococci listed . only S. oralis ATCC 55229 coaggregates with
C. ochracea ATCC 33596.
S. oralis ATCC 55229 contains a quite different surface receptor that lacks N-
acetylated sugars.
- The repeating hexasaccharide is not linked by phosphodiester bonds, but
rather the phosphate is found as a glycerol phosphate substitution on an internal
galactose moiety .
- The coaggregation is sensitive to lactose and galactose, 16-fold more sensitive
to L-rhamnose, but insensitive to GalNAc.
60. 5. Dispersion
• Once biofilms are established, planktonic bacteria may periodically leave the biofilm
on their own. When they do, they can rapidly multiply and disperse.
• Biofilm bacteria can move in numerous ways: collectively, by
• Rippling or rolling across the surface
• Detaching in clumps.
• Individually, through a “swarming and seeding” dispersal.
61. • Dispersal of cells from the biofilm colony is an essential stage of
the biofilm lifecycle.
• Dispersal enables biofilms to spread and colonize new surfaces
62. INNOVATIONS AND FUTURE
RESEARCH
•Understanding these methods of bacterial-
bacterial interactions and bacterial-host
interaction develops new strategies to
inhibit bacterial adhesion as seen in the
diagram
63. • The principle of oral disease vaccines is to induce antigen specific antibodies against
the causative agent or agents that inhibit the infection process by one of 3 main
mechanisms:
1. Antibody-mediated clearance,
2. Blocking of essential receptors required for microbial attachment,
3. Inhibition of enzymes required for metabolism or colonization.
• For mutans streptococci, 3 proteins are promising vaccine candidates:
AgI/II family polypeptide SpaP, GTF, and GbpB (Taubman and Nash, 2006).
• However, dental caries is not associated just with S. mutans; therefore, vaccines
targeting only these organisms may not be 100% effective
64. • No clinical trials have been performed to date against periodontitis. Nonetheless,
animal models have shown that vaccines against fimbriae, gingipains, or OMPs can
successfully interfere with P. gingivalis colonization and reduce periodontal bone
resorption (Persson, 2005; Beevi et al., 2009).
• Molecular information about adherence mechanisms can also be exploited in the
design of replacement therapies, attachment-blocking peptides, and biomimetics or
signaling inhibitors to disrupt microbial community development. (Nobbs et al.,
2009; Chen and Wang, 2010).
