Biofilm 2 - Periodontal Flashcards
What pathogens are associated with PD disease?
red complex
- Porphyromonas gingivalis
- Tannerella forsythia (previously Bacteroides forsythus)
- Treponema denticola
What are the orange and green complex bacteria?
🟠 Orange Complex –
👉 Bridging between health & disease
Fusobacterium nucleatum
Prevotella intermedia
🟢🔵🟡 Green/Blue/Yellow Complexes
👉 Associated with health
Streptococcus spp.
Actinomyces
How does the biofilm cause periodontal disease?
drivers of dysbiosis
- Presence of red complex bacteria
- Biofilms persist within community surrounded by
extracellular matrix (glycocalyx)
Environmental changes and inflammation promote overgrowth of pathobionts, shifting from saccharolytic (sugar-based) to proteolytic (protein-based) metabolism.
What are the interactions that pathogens have in the oral biome?
Competition (dominance)
* Metabolic products – acids, oxidants
* Bacteriocins
Co-operation (integration)
* Metabolic products – saccharides, peptides, growth factors
* Adhesion substrates
* Immune avoidance
What are the characteristics of p.gingivalis?
- Commonly isolated in periodontal disease
- Gram negative rod, obligate anaerobe (cannot survive in the presence of oxygen)
What are the virulence factors of p.gingivalis?
- Host cell tissue adherence and invasion through fimbriae
- Endotoxin (LPS)
- Outer membrane vesicles
- Proteases (including gingipains)
- Metabolic byproducts
What are gingipains?
- Multifunctional proteins
- Proteolytic, hemagglutinin, adhesion activity and
hemin binding - Damage host cell
- Degradation of cytokines and complement proteins
- Provide nutrition to the cell
How does p.gingivalis subverse the immune system?
- Neutrophil subversion through gingipains activating toll like receptors TLR
- Degradation of antimicrobial peptides
- Inflammatory response without bactericidal effects
- Selection for pathogenic species
What is a periodontal pathogen that is asssociated with aggressive periodontitis?
not part of the red complex
Aggregatibacter Actinomycetemcomitans
What are the virulence factors of aggregatibacter actinomycetemcomitans?
- Leukotoxin (interference with host responses)
- LPS (inflammation)
- Antibiotic resistance
- Fimbrae
- A range of enyzmes which damage tissues and bone resoption
How were the bacterial pathogens cultured?
Paper points (subgingival plaque)
Fast culturing or anaerobic transport
FAA (agar) + blood & hemin
Black colonies = P. gingivalis
Gram-negative rods
Antibiotic sensitivity testing (Disk Diffusion or MIC)
What molecular methods were used to identify known species?
- qPCR – Specific primers targeted at key species
- MALDI-TOF following culture
- Multi-locus sequence typing (identifies variations in housekeeping genes to characterise strains)
What molecular methods were used to identify unknown species?
- 16S Sequencing – traditionally Sanger (NGS also applicable)
- Whole Genome Sequencing (WGS)
How were entire communities identified?
which molecular methods
- 16S Sequencing
- WGS
How does 16s amplicon sequencing work?
- 16S genes encode the small subunit of the ribosome - Ubiquitous but hypervariable
- 9 distinct hypervariable regions V1-V9
- Vary dramatically in their genetic sequence between species and strains
- This signature can be used to identify the specific organism and its abundance.
