BK - Gut Ecology Flashcards
Where do biofilms cause the most trouble?
Biofilms, slimy communities of bacteria, can wreak havoc in various parts of the body:
Primary sites:
- Mouth: Dental plaque formation leading to cavities and gum disease.
- Subcutaneous tissues: Infections around catheters and implanted devices.
Secondary sites:
- Brain: Can cause meningitis.
- Kidneys: Can lead to urinary tract infections (UTIs).
- Spine: Can cause infections between vertebrae.
How does dental plaque wreak havoc? (3)
Bacteria: Streptococcus mutans and others ferment sugars, producing acids that erode teeth (cavities)
Biofilm structure: Plaque forms a sticky layer, protecting bacteria from the immune system and making removal difficult
Consequences: Cavities, gum inflammation (gingivitis), and gum tissue destruction (periodontitis).
Biofilms and medical devices (2)
- Catheters and implants can provide a surface for bacteria to adhere and form biofilms.
- Biofilms on these devices can lead to serious infections that are difficult to treat
What other organs can be affected by biofilm infections? (3)
- Heart valves (endocarditis)
- Urogenital tract (STIs like gonorrhea, syphilis)
- Bones (osteomyelitis)
What is the oral microbiome and how can it become imbalanced?
The oral microbiome is a complex community of bacteria in the mouth. It can shift from a healthy state to a disease-causing one (dysbiosis)
How does the body defend itself from harmful oral bacteria? (3)
The body employs various physical and chemical barriers to maintain oral health:
- Physical: Keratinized epithelium (skin lining), mucin production (lubricating mucus), and salivary flow (washing away debris).
- Chemical: Enzymes and antibacterials in saliva, and gingival fluid secretions containing immune components
- Inflammatory reaction
How do babies acquire their oral flora?
Acquisition of the Oral Flora (Early)
- Acquisition of oral flora depends upon exposure at the time of birth, cesarean or vaginal. Shortly thereafter, caregivers provide the next insult of microorganisms
Acquisition of the Oral Flora (Later)
- After tooth eruption: organisms favouring hard tissue e.g. Strep. sanguis and Strep. mutans, Actinomyces spp.
Colonisation of crevicular tissues: anaerobic organisms e.g. Prevotella spp.
Loss of teeth: “a 2nd childhood microflora”
Prosthetic appliance: e.g. dentures - similar to enamel plaque, may harbor large numbers of yeast
What is dental caries (cavities) and what factors contribute to it?
Cavities are holes in teeth caused by acid erosion
- High sugar intake and poor oral hygiene are major risk factors.
How does gingivitis differ from periodontitis?
- Gingivitis is gum inflammation caused by plaque buildup and poor hygiene
- Periodontitis is a more advanced stage with bone loss, often linked to specific bacteria
How do Streptococcus mutans bacteria contribute to cavities? (4)
Streptococcus mutans possess several virulence factors that promote cavities:
- Saccharolytic: Break down sugars into acids (acidogenic).
- Glucosyltransferases: Produce sticky glucans that form plaque biofilm (glucosyltransferase).
- Fructosyltransferases: Contribute to plaque formation (fructosyltransferase).
- Acidogenic: Ferment sugars to lactic, acetic, and formic acids, lowering the pH and eroding tooth enamel (aciduric)
What is the role of Veillonella in the oral cavity? (3)
- Gram-negative anaerobic cocci.
- Thrives in the acidic environment of caries and is thought to slow the development of dental caries.
- Converts the lactic acid of other species to less acidic products.
How are Lactobacillus bacteria associated with dental caries? (4)
- Gram-positive facultative anaerobes.
- Normally symbiotic in humans and found in the gut flora.
- Some species with increased numbers in plaque associated with carious lesions.
- “Microbial indicator of disease state” (with S. mutans etc)
What role do Fusospirochetes play in oral health?
In cases of bleeding gums, Fusospirochetes can contribute to infection and diseases like:
- Acute necrotizing ulcerative gingivitis (ANUG) - also referred to as “trench mouth”
- Vincent’s angina.” It’s caused by a combination of anaerobic bacteria including Prevotella intermedia, Fusobacterium, Treponema, and Borrelia spp
What are the three main bacterial culprits in chronic periodontitis?
Treponema denticola
- Gram-negative anaerobic spirochete.
- Elevated levels are found in patients with periodontitis.
- Considered the most important of the three due to its motility and highly proteolytic nature, contributing to tissue destruction.
Porphyromonas gingivalis
- Gram-negative oral anaerobe strongly associated with chronic adult periodontitis. Produces a number of well-characterized virulence factors.
Aggregatibacter actinomycetemcomitans
- Gram-negative facultative non-motile rod, association with localized aggressive periodontitis in young adolescents and bone loss.
- Virulence factors: leukotoxin kills PMNs and moncytes; cytolethal distending toxin; immunosuppression factors that inhibit blastogenesis, antibody production and activate T-suppressor cells
What is the order of colonization in plaque formation? (4)
- Salivary Proteins: Provide an initial adhesive layer on the tooth surface.
- Pioneer Species: Bacteria like Streptococcus mutans attach to the salivary layer, initiating biofilm formation.
- Secondary Colonizers: Species like Veillonella join the community, creating a more complex structure.
- Tertiary Colonizers: Further diversify the biofilm with a wider range of bacterial species.
