Biofilm / Diet

Question 1

Resident microflora

Answer 1

diverse composition, gram positive and negative bacteria

early colonizers: streptococcus salivarius, streptococcus mitis, streptococcus oralis

With time, gram-negative anaerobes including prevotella melaninogenica, fusobacterium nucleatum, veillonella spp. appear.

Question 2

Cross talk in resident microflora

Answer 2

Communication between host and resident microflora to maintain a beneficial and symbiotic relationship

Question 3

Development of biofilm stages

Answer 3

1.) Pellicle formation (minutes)
2.) Attachment of early colonizers (0-24 hrs)
3.) Microcolony formation by co-adhesion and growth (4-24 hrs)
4.) Species diversity through microbial succession (1-7 days)
5.) Mature biofilm (1 week / older)

Question 4

Biofilm structure

Answer 4

made of microcolonies (15-20% volume) distributed in shaped matrix (75-80% volume)

Presence of voids and water channels

Exopolysaccharides (EPS): backbone of biofilm

Physiological heterogeneity within biofilm

Question 5

Bacterial Metabolic Pathways

Answer 5

Glucose comes into cell via PEP-PTS enzyme, PEP ->PYR

Veillonella uses Lactate to make lactic acid. forms acetate, formate to reduce pH in biofilm

Xylitol in and out, using PEP-PTS system. Xylitol cannot be used by bacteria to form ATP so it is spit out and constantly repeated. Bacteria starves because it cant make the ATP needed.

glucosyltransferase/fructosyltransferase produce fructon/glucon (sticky matrix in biofilm) from sucrose

Question 6

Biofilm composition by site

Answer 6

Within fissures: normal microflora of fissures is sparse. Streptococci predominate with few gram-negative / anaerobic organisms.

Gingival crevice: more diverse microflora, more gram negative / anaerobic organisms.

Approximal surfaces: combination of microflora of both fissures / gingival crevices.

Question 7

Streptococcus mutans facts

Answer 7

Facultative anaerobic

Gram positive coccus

0.5-0.75 um in diameter

Question 8

6 Species associated with severe caries

Answer 8

S. mutans

Actinomyces Gerencseriae

Bifidobacterium spp.

S. salivarius

Lactobacillus fermentum

Veillonella spp.

Question 9

Carbohydrate classification

Answer 9

monosaccharides: glucose fructose galactose

disaccharides: sucrose maltose lactose

oligosaccharides (3-15 monosaccharides)

polysaccharides (large polymer of simple sugars) : starch glycogen cellulose

Question 10

Resident microflora prevent overgrowth of pathogenic organisms by:

Answer 10

Saturation of microbial attachment sites

Effective competition with essential nutrients

Creating unfavorable conditions to invading microbes

Production of inhibitory factors.

Question 11

Caries prevention strategies

Answer 11

limit eating / drinking between meals

be mindful of sugar beverages

stimulation of saliva flow after main meals

brush 2x a day, floss