Biofilms 1 - Caries Flashcards
What is the formal definition of a biofilm?
Matrix-enclosed microbial populations (aggregates) adherent to each other and/or to surfaces or interfaces
Describe the stages of biofilm development in chronological order.
Attachment
Colonization
Development/maturation
Release
What are the five key characteristics of biofilms mentioned in the summary section?
1) Predominant form of microbial growth in natural environments
2) Can be single species or mixed species,
3) Individual cells embedded in a matrix of extracellular polymers
4) Resistance to antimicrobial agents and the immune system
5) Biofilm cells are phenotypically distinct (the biofilm phenotype)
List all the oral diseases mentioned in the lecture that involve biofilms.
Caries, Gingivitis and Periodontal Disease, Denture Stomatitis (Candidal Biofilms), Angular Cheilitis, and Endodontic Infections
Which bacteria are identified as early colonizers in dental plaque?
Streptococci
What are the five progressive stages in caries development?
Adhesion → Survival & growth → Biofilm formation → Complex plaque → Acid → Caries
What is the critical pH threshold for the process of demineralization and remineralization?
5.5
What are the characteristics of strep mutans?
- Facultative anaerobe (with or without oxygen)
- Gram Positive
- Cocci shape
- Large amount of evidence within the scientific literature implicating S. mutans
- Linked to caries in the “specific plaque hypothesis”
- Linked to high levels of sugar in the diet
What are the key virulence mechanisms of S. mutans? List all mentioned in the lecture.
- Adhesins (to pellicle)
- Glucosyltransferases (Gtfs)
- Biofilm formation
- Acid Production and Tolerance
- Bacteriocins
- Production of EPS (particularly in the
presence of sucrose) through biofilm and glucans
Explain how sucrose contributes to two fundamental virulence factors of S. mutans.
1) Fermentation of sucrose produces lactate (acid)
2) Sucrose is used by Glucosyltransferases to produce Glucans, which increase biofilm formation
How does S. mutans adapt to low pH environments?
S. mutans utilizes proton pumps to expel H⁺ ions from the cell, allowing it to tolerate acidic conditions
Besides S. mutans, list at least five other bacterial genera associated with caries development.
Actinomyces, Abiotrophia, Atopobium, Bifidobacterium, Lactobacillus, Veillonella, Propionibacterium, Prevotella
What are the three major hypotheses regarding the etiology of dental plaque that have evolved over time?
Non-specific Plaque Hypothesis” → “Specific Plaque Hypothesis” → “Ecological Plaque Hypothesis
What is the concept of “redundancy of microbes” in relation to caries biofilms?
Multiple different species share common functional capabilities (such as acid production and tolerance), making them all potentially important in caries development rather than just a single species
What observation challenges the exclusive role of S. mutans in caries development?
S. mutans is not always present in caries (variable findings from clinical studies), and many organisms associated with caries are also found in health
Compare and contrast the four main approaches to identifying microbes in caries.
1) Culture methods (traditional growth on selective media)
2) Molecular methods (PCR, sequencing)
3) DNA markers
4) Metabolic/Protein approaches (e.g., MALDI)
What selective agar is specifically used to identify S. mutans, and under what conditions is it grown?
Mitis Salivarius Bacitracin (MSB) agar in CO₂ at 37°C
What are the key benefits of molecular methods for identifying microbes in caries?
Increased specificity for speciation of organisms and identification of non-culturable organisms
What principle regarding food retentivity was mentioned using the phrase “Sticky in the hand, sticky in the mouth”?
Retentivity of food may be crucial for cariogenicity, not just sugar content
What is meant by “microbiome resilience” in the context of oral health?
Some individuals are less susceptible to dysbiosis due to the buffering capacity and composition of their oral microbiome
Under normal conditions, what protects the pulp from infection?
Intact enamel and dentine
How are endodontic infections generally classified in terms of their origin?
They are classified as opportunistic infections derived from endogenous microflora
What are the primary routes through which infections reach the pulp?
Secondary to tooth infections/trauma (e.g., caries caused by Streptococci & Lactobacilli)
List the seven most common bacterial genera found in endodontic infections
Bacteroides (70%)
Prevotella (60%)
Lactobacillus (51%)
Streptococcus (oral) (41%)
Clostridium (36%)
Fusobacterium (33%)
Propionibacterium (29%)
