Microbes in oral health

Question 1

Which is the most common global health condition?

Answer 1

tooth decay (affects 34% of global population)

Question 2

What is the oral microbiome?

Answer 2

The sum of microbes, their genetic information and the environment in which they interact

Question 3

What makes up the oral microbiome?

Answer 3

bacteriome, virome, mycobiome, archaeome, protozoome

Question 4

Aspects of the macrobiome that can impact the microbiome

Answer 4

socioeconomic status, oral hygiene, smoking, education, income

Question 5

Example of macrobiome impacting microbiome

Answer 5

socioeconomic status impacts caries (higher decay rate in most deprived children)

Question 6

Example of 2 keystone pathogens

Answer 6

Streptococcus mutans and Porphyromonas gingivalis

Question 7

Description of Streptococcus mutans (gram stain and shape)

Answer 7

gram positive (purple). cocci in chains

Question 8

How is Streptococcus mutans held together in chains?

Answer 8

By exopolysaccharide

Question 9

What are the virulence factors of Streptococcus mutans?

Answer 9

1. Lactic acid production
2. Acid tolerance (favoured by pH < 5.5)
3. Extracellular polysaccharide synthesis (protective)
4. Biofilm formation

Question 10

Description of symbiosis between the host and microbiome

Answer 10

plaque is dominated by commensal bacteria, low net acid production, no net demineralisation

Question 11

Description of dysbiosis between host and microbiome

Answer 11

plaque dominated by pathogenic bacteria, high net acid production, net enamel demineralisation

Question 12

Why does symbiosis occur?

Answer 12

an infrequent sugar intake means there is decrease pathogenic metabolism but increased commensal metabolism so there is a decreased bacterial load.

Question 13

Why does dysbiosis occur?

Answer 13

frequent sugar intake increases pathogenic metabolism and decreases commensal metabolism so there is an increased bacterial load.

Question 14

Stages of the ecological plaque hypothesis in caries aetiology

Answer 14

1. fermentable carbohydrates lead to acid production
2. environment has a lower pH
3. Ecological shift from symbiosis to dysbiosis as pathogenic bacteria are favoured (S. mutans, Lactobacilli)
4. caries (disease)

Question 15

What is required for caries to develop?

Answer 15

tooth surface, bacteria, time, fermentable carbohydrates

Question 16

Which is the keystone pathogen in periodontitis?

Answer 16

Porphyromonas gingivalis

Question 17

Description of Porphyromonas gingivalis (gram stain, shape, growth medium)

Answer 17

gram negative, bacilli (coccobacilli), black pigmenting anaerobe (O2 is toxic, black - absorbs haem from blood agar)

Question 18

What are the virulence factors of Porphyromonas gingivalis?

Answer 18

1. increased resistance to phagocytosis (local chemokine paralysis, cleave complement proteins)
2. can cause an inflammatory response (LPS type 1 - TLR4 agonist)
3. releases outer membrane vesicles (OMV - contain enzymes like gingipains to cleave complement proteins and inhibit IL-8 synthesis)
4. capsule

Question 19

Description of the ecological plaque hypothesis for periodontal disease

Answer 19

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)

Question 20

What is Eh?

Answer 20

Redox potential - a high Eh increases bacteria associated with ecological balance

Question 21

Facultative anaerobes meaning

Answer 21

microbes that survive with/without O2

Question 22

Obligate anaerobes meaning

Answer 22

microbes that can only survive in absence of O2

Question 23

Example of statistic demonstrating the effect of macrobiome on periodontal status

Answer 23

individuals in the most deprived areas had an average of 4.6 fewer sound teeth than those in the least deprived areas