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Oral Flora I
Karen Ross
2007
Anaerobic Bacteria of Clinical Importance
Genera
Bacilli (rod)
Gram-negative
Bacteroides
Fusobacterium*
Gram-positive
Anatomic Site
Colon
Mouth, Colon
Tannerella*
Mouth
Prevotella*
Mouth
Porphyromonas*
Mouth
Actinomyces*
Lactobacillus
Propionibacterium
Eubacterium,
Bifidobacterium and Arachnia
Clostridium
Cocci (spheres)
Gram-positive
Peptostreptococcus
Gram-negative
Veillonella*
Mouth
Mouth, Vagina
Skin
Mouth, Colon
Colon, also found in the soil
Colon
Mouth, Colon
Porphrymonas gingivalis
•
•
•
•
Gram -ve coccobacilli
Anaerobic, dark pigmentation on media containing lysed blood.
Black pigmentation due to accumulated hemin used as an iron source
for growth
The diseases collectively termed periodontitis are bacterial infections
which begin with inflammation of the periodontium, and can progress
to loss of teeth. Untreated infections lead to destruction of the
periodontal ligament and alveolar bone. It is estimated that over
49,000,000 people in the United States have some form of
periodontitis (Cutler et al., 1995). These diseases are infectious
conditions which may progress over several years with episodes of
exacerbation and remission. Periodontitis occurs with higher
frequency in patients with systemic diseases such as diabetes
mellitus, AIDS, leukemia, neutropenia, Crohn's disease, and Down's
syndrome (Neville et al., 1995)
Virulence Factors of P.g
Molecules and Organelles
Proteases -arginine and lysine specific cysteine
proteases
Hemagglutinins -mediate the binding of Pg to
epithelial cells and erythrocytes
LPS-very different composition from enteric
bacteria lacks endotoxicity
Fimbriae -peritrichous (all directions), neccesary
for infection
Outer membrane vesicles -outgrowth of outer
membrane, platelet aggregation, precise
delivery of virulence factors, can enter where
Pg cannot
Polysaccharide capsule -six serotypes, reduced
phagoscytosis
Cytotoxic metabolic end products -include
butyrate, propionate, have low molecular
weights which allows them to easily penetrate
periodontal tissue and disrupt the host cell
activity
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Tsute Chen, Department
of Molecular Genetics,
The Forsyth Institute.
Mechanisms
Adhesion, colonization and dental plaque
(biofilm) formation
Epithelial and Endothelial cell invasion
Proteolysis - proteases degrade host proteins
including fibrinogen, plasma proteins, cytokines,
can also activate neutrophils
Inflammatory response -can activate and suppress
components of the innate immune response.
Bone resorption, bone destruction, and bone
formation inhibition -LPS, fimbrial and outer
membrane consituents play a major role. Eg. LPS
causes release of bone resorption mediators
(cytokines) from fibroblasts, macrophages and
monocytes. These mediators also induce host cell
proteases that destroy both bone and connective
tissue and inhibit synthesis of collagen by
osteoblasts.
(Lamont et al., 1995)
CCR5 tropic HIV-1
Porphyromonas
gingivalis
CXCR4 tropic HIV-1
Oral
keratinocytes
HIV target
CD4(+) T cells
CCR5
gingipains
LPS
PAR 1-2
CCR5
TLR 2-4
Endosome
CCR5
CD4
CCR5
Other HIV receptors
Courtesy of Rodrigo Giacaman-Sarah; Herzberg Lab
Morphological changes of epithelial cells
after exposure to P. gingivalis
Morphological changes were delayed in KB-MRP8/14.
Morphological changes of epithelial cells
after exposure to P. gingivalis for 24 h
wild type
fimbriaedeficient
mutant
P. gingivalis proteases
Cysteine proteases
• Arg-gingipain, RgpA, RgpB
• Lys-gingipain, Kgp
Morphological changes of epithelial cells after exposure to P. gingivalis
wild type and protease-deficient mutants for 24 h
Strain
Phenotype
ATCC33277
Wild type
KDP129
Kgp-deficient
mutant
KDP133
RgpA, RgpBdeficient mutant
KDP136
Kgp, RgpA, and
RgpB-deficient
mutant
Cells expressing calprotectin are more resistant to cell
detachment mediated by P. gingivalis proteases, Kgp
and Rgp.
Seok-Woo Lee,
School of Dental and Oral Surgery
Columbia University
Tannerella forsythia
Gram -ve, filament shaped, non motile, non pigmented
Anaerobe
Virulence factors
Hydrolases -produces a trypsin-like protease, and an arginine-specific
cysteine protease, and a sailase.
Hemolytic activity -cyteine protease, iron acquisition from erythrocytes
Co-aggregation -P. gingivalis, S. cristatis
Adhesion -leucine rich surface protein (BspA), binding to RBCs,
fibroblasts, leukocytes, and epithelial cells (see above)
Treponema denticola
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Motile helical rods
Irregular (3-8) spirals
Gram-ve cell wall
Anaerobe, able to be grown in vitro
'TREPONEMA DENTICOLA’
by Joe Dixon, 2007
Molecules
Major outer membrane protein(Msp) - 53kDa adhesin with pore forming activity,
cytotoxic for epithelial cells and erythrocytes
Proteinases -Dentilisin/PrtP/CTLP involved in
cell attachment, tissue destruction, tissue
invasion
Hemin- and lactoferrin-binding proteins iron acquisition and utilises lactoferrin from
the saliva
Treponema denticola
T. d induces actin rearrangement and
detachment of human gingival
fibroblasts. Baehni et al., 1992
Mechanisms
Motility and chemotaxis - motility
mutants fail to infect their hosts.
Maneuvering in viscous fluids, gingival
crevice is highly viscous.
Hemagglutination and hemolytic activity
Adhesion - Fibroblasts, extracellular
matrix, epithelial cells, endothelial cells
coaggregation
Invasion-Tissue and cellular invasion,
produce lesions in tissue models,
penetrate epithelial and endothelial cell
monolayers
Proteolytic activity Dentilisin/PrtP/CTLP
disrupts cell junction and impairs
epithelial monolayers
Immunosupppressive activity lymphocyte proliferative responses to
antigens and mitogens suppressed
Fusobacterium
nucleatum
Gram -ve, anaerobic, cigar-shaped bacilli with pointed ends
Recovered mainly from periodontal pockets
In combination with oral spirochaetes) causes fusospirochaetal
infections -acute necrotizing ulcerative gingivitis, vincents
angina, cancrum oris or noma
Toxic metabolites -butyrate, proprionate, ammonium ions
Coaggregation -anchor, bridge formation
Adhesion -binds to fibronectin
-binds PMNs, macrophages, lymphocytes, HeLa
cells, fibroblasts, both periodontal ligament and gingival
fibroblasts and buccal epithelial cells
Invasion -epithelial cells
Collaborative invasion
Tissue culture experiment
F. nucleatum invades
epithelial cells
S. cristatus does not invade
cells
After coaggregation, S.
cristatus is carried inside by
F. nucleatum
Edwards, Grossman, and Rudney 2006, Infect Immun 74: 654
Prevotella intermedia
Anaerobic, Non-motile,
Short, round-ended, Gram-ve rods
Virulence
Fimbriae -4 different types
Hydrolases
Hemolysin and hemagglutinin
Coaggregation
Adhesion
Invasion
Induction of inflammatory lymphokines
Veillonella spp.
• V. parvula, V. dispar, V. atypica
• Non-motile, nonsporulating, small, anaerobic Gram-ve
cocci
• Commensals of the oropharynx, gastrointestinal tract
and female genital tract
• Unable to use carbohydrates or amino acids, ferment
organic acids to propionic and acetic acids, CO2 and H2
• Component of early plaque, may use lactic acid
produced by streptococci the early colonisers -metabolic
cooperation
Capnocytophaga spp.
C. gingivalis
C. ochracea
C. sputingena
C. granulosa
C. haemolytica
Hydrolases
Trypsin-like protease
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Actinomyces
• Gram+ve anaerobic and microaerophilic
• Filamentous, branching,gram-positive rods.
Older microbiologists sometimes referred to
actinomyces as fungi because of the were
long like fungal hyphae. However, they are
only about a tenth as wide.
• They normally reside in the human mouth, throat, large intestine,
vagina, and the crevices between teeth and gums, especially
underneath dental plaque.
• Normal flora and is not transmitted from person to person.
• Not usually virulent, reside as saprophytes in the body without
producing disease.
• Problem only if they have the opportunity to grow on a surface
away from oxygen. They stick to one another, and eventually can
break loose as a mass that is too big to be engulfed by the body's
defense cells.
Actinomycosis
•
•
•
•
•
Actinomyces israelii
Tooth abscess or a tooth extraction and the endogenous organism becomes
established in the traumatized tissue and causes a suppurative infection(pus).
These abscesses are not confined to the jaw and may also be found in the
thoracic area and abdomen.
The patient usually presents with a pus-draining lesion, so the pus will be the
clinical material you send to the laboratory.
Yellow sulfur granules, characteristic of this organism, can be seen with the
naked eye. You can also see these granules by running sterile water over the
gauze used to cover the lesion. The water washes away the purulent material
leaving the golden granules on the gauze.
• Aggregation
• Co-aggregation
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Fusobacterium nucleatum cells
coaggregating with Porphyromonas
gingivalis cells.
Fusobacterium nucleatum intergeneric
coaggregations in the form of corn-cob formations
Kolenbrander et al., 2000
Advantages of co-aggregation
Physical contact -attachment
Metabolic exchange
Small-signal-molecule-mediated
communication
Exchange of genetic material
Kolenbrander et al., 2006
Streptococcus oralis in
three-fold excess over
partner Prevotella loescheii
(arrows)
Fusobacterium nucleatum
P. loeschii does not
coaggregate with F.
nucleatum but S. oralis
coaggregates with both
and acts as a
coaggregation bridge
Kolenbrander et al., 2006
Kolenbrander
2006
Reviews: light reading :)
Socransky and Haffagee
Periodontal microbial ecology
Periodontology 2000
Vol 38:135-187, 2005
Kolenbrander et al.,
Bacterial interactions and sucessions during plaque
development
Periodontology 2000
Vol 42: 47-79, 2006