Microbes in oral health Flashcards
Which is the most common global health condition?
tooth decay (affects 34% of global population)
What is the oral microbiome?
The sum of microbes, their genetic information and the environment in which they interact
What makes up the oral microbiome?
bacteriome, virome, mycobiome, archaeome, protozoome
Aspects of the macrobiome that can impact the microbiome
socioeconomic status, oral hygiene, smoking, education, income
Example of macrobiome impacting microbiome
socioeconomic status impacts caries (higher decay rate in most deprived children)
Example of 2 keystone pathogens
Streptococcus mutans and Porphyromonas gingivalis
Description of Streptococcus mutans (gram stain and shape)
gram positive (purple). cocci in chains
How is Streptococcus mutans held together in chains?
By exopolysaccharide
What are the virulence factors of Streptococcus mutans?
- Lactic acid production
- Acid tolerance (favoured by pH < 5.5)
- Extracellular polysaccharide synthesis (protective)
- Biofilm formation
Description of symbiosis between the host and microbiome
plaque is dominated by commensal bacteria, low net acid production, no net demineralisation
Description of dysbiosis between host and microbiome
plaque dominated by pathogenic bacteria, high net acid production, net enamel demineralisation
Why does symbiosis occur?
an infrequent sugar intake means there is decrease pathogenic metabolism but increased commensal metabolism so there is a decreased bacterial load.
Why does dysbiosis occur?
frequent sugar intake increases pathogenic metabolism and decreases commensal metabolism so there is an increased bacterial load.
Stages of the ecological plaque hypothesis in caries aetiology
- fermentable carbohydrates lead to acid production
- environment has a lower pH
- Ecological shift from symbiosis to dysbiosis as pathogenic bacteria are favoured (S. mutans, Lactobacilli)
- caries (disease)
What is required for caries to develop?
tooth surface, bacteria, time, fermentable carbohydrates
Which is the keystone pathogen in periodontitis?
Porphyromonas gingivalis
Description of Porphyromonas gingivalis (gram stain, shape, growth medium)
gram negative, bacilli (coccobacilli), black pigmenting anaerobe (O2 is toxic, black - absorbs haem from blood agar)
What are the virulence factors of Porphyromonas gingivalis?
- increased resistance to phagocytosis (local chemokine paralysis, cleave complement proteins)
- can cause an inflammatory response (LPS type 1 - TLR4 agonist)
- releases outer membrane vesicles (OMV - contain enzymes like gingipains to cleave complement proteins and inhibit IL-8 synthesis)
- capsule
Description of the ecological plaque hypothesis for periodontal disease
plaque accumulation leads to increased inflammation. Environment changes to favour obligate anaerobes to thrive (lower Eh, higher temp, higher pH). There is an ecological shift to predominantly gram-negative, red complex, obligate anaerobes (ecological catastrophe)
What is Eh?
Redox potential - a high Eh increases bacteria associated with ecological balance
Facultative anaerobes meaning
microbes that survive with/without O2
Obligate anaerobes meaning
microbes that can only survive in absence of O2
Example of statistic demonstrating the effect of macrobiome on periodontal status
individuals in the most deprived areas had an average of 4.6 fewer sound teeth than those in the least deprived areas
