L4: The microbial flora of dental plaque

Question 1

what is colonization resistance?

Answer 1

when normal flora acts to exclude pathogens and protect the host

Question 2

on what sites of the body can microbial colonosation take place?

Answer 2

hard & non-shedding surfaces

Question 3

tongue crypts have a ____ redox potential

Answer 3

low

Question 4

what do the low redox potential of tongue crypts mean for gram -ve anaerobes?

Answer 4

acts as a reservoir for gram -ve anaerobes = periodontal disease

Question 5

____ and ___ _____ of saliva at different oral sites may influence caries susceptibility

Answer 5

flow and ion content

Question 6

what is the role of glycoproteins in saliva?

Answer 6

• influeneces aggregation and adhesion of bacteria to oral surfaces
• interacts with other salivary components and immune defences
• acts as a primary source of nutrients for normal microflofora

Question 7

what is the role of urea and free amino acids in saliva?

Answer 7

they are metabolised to lead to an increased pH (counteracts acid production after carb intake)

Question 8

what is GCF and what does it do?

Answer 8

gingival crevicular fluid; regulates the microflora of the gingival crevice during health and disease

Question 9

what are the non-specific factors of saliva?

Answer 9

• physical removal by flow of saliva & GCF
• swallowing
• LYSOZYME in saliva hydrolyses peptidoglycan in bacterial cell walls
• LACTOFERRIN - high affinity iron - binding glycoprotein
• SIALOPEROXIDASE - salivary peroxidase enzyme system generates inhibitors of bacterial glycolysis
• antimicrobial peptides (i.e. histatins - histadine rich peptides) that regulate microorgansm levels

Question 10

what are the specific factors in saliva

Answer 10

• intra-epithelial lymphocytes, langerhan cells & IgA found within the mucosa - acts as a barrier to penetratng antigens
• secretory IgA - agglutinates bacteria, modulates enzyme activity & inhibits adherence of bacteria to buccal epithelium and enamel.
• CGF conatins IgG, IgM, IgA, complement and neutrophils
• specific Ab production stimulated by bacterial antigens at the gingival margin or on oral mucosa

Question 11

stroptococcus is gram ___

Answer 11

+ve

Question 12

extracellular polysaccharides are associated with

Answer 12

plaque formation

Question 13

what are the 2 strains present in the streptococcus mutans group?

Answer 13

S.mutans

S.sobrinus

Question 14

what 2 isolates are present in the aetiology of enamel caries in children and young adults?

Answer 14

dental caries

Question 15

what are the two main strains of the Streptococcus salivarius group?

Answer 15

• S. salivarius – common isolate from most areas
esp. mucosal surfaces.
• S. vestibularis – isolated mainly from vestibular
mucosa of mouth.

Question 16

where is s. vestibularis found?

Answer 16

mainly at the vestibular mucosa of the mouth

Question 17

what are the 3 main strains of the streptococcus milleri group?

Answer 17

S.constellatus, S.intermedius & S.anginosus

Question 18

what type of pathogens are the streptococcus milleri group? (S.constellatus, S.intermedius & S.anginosus)

Answer 18

Opportunistic pathogens – important cause of

purulent disease

Question 19

name 2 strains of the streptococcus oralis group?

Answer 19

S.sanguinis, S.gordonii

Question 20

what type of pathogens are the streptococcus oralis group? (what type of pathogens are the streptococcus milleri group? (S.sanguinis, S.gordonii)

Answer 20

• Opportunistic pathogens – isolated frequently

from infective endocarditis

Question 21

what type of bacteria is Peptostreptococcus spp (P. anaerobius)

Answer 21

obligate anaerobes

Question 22

where is Peptostreptococcus spp (P. anaerobius) recovered from?

Answer 22

Recovered from dental plaque esp. in
advanced periodontitis, carious dentine,
infected pulp chambers and root canals, and
dental abscesses.

Question 23

where is Enterococcus (E.faecalis) recovered from?

Answer 23

Recovered in low nos. from several oral

sites – involved in root canal infections.

Question 24

where are Staphylococci and micrococci found?

Answer 24

not members of the resident oral microflora – may be present transiently

Question 25

what is Rothia?

Answer 25

aka Stomatococcus mucilaginosus a species of Gram-positive, round- to rod-shaped bacteria that is part of the normal community of microbes residing in the mouth and respiratory tract.

Question 26

where is Rothia rothia | (Stomatococcus) mucilagenous found?

Answer 26

isolated | from tongue

Question 27

Actinomyces

Answer 27

gram +ve Forms a major portion of plaque microflora esp. at approximal sites – also colonise gingival crevice – nos increase with gingivitis and are associated with root surface caries. A.israelii can act as opportunistic pathogen and cause actinomycosis

Question 28

Eubacterium

Answer 28

``` gram +ve • Poorly-defined genus – obligate anaerobes • Found in subgingival plaque esp. in periodontitis • Often isolated from infections of head, neck and lung and necrotic dental pulp ```

Question 29

Lactobacillus

Answer 29

gram +ve • Commonly isolated although comprise <1% of total cultivable flora • Little known of preferred habitat in normal mouth • Proportions and prevalence increase at advanced caries lesions of enamel and root surface – highly acidogenic organisms

Question 30

Propionibacterium

Answer 30

• Obligate anaerobes – several spp. reported from mouth incl P. acnes in dental plaque P. propionicus – opportunistic pathogen & isolated from actinomycosis

Question 31

Neisseria

Answer 31

``` gram -ve • Aerobic – isolated in low numbers from most sites in mouth • With S.oralis-group are among early colonisers of a clean tooth surface ```

Question 32

Veillonella

Answer 32

gram -ve • Strict anaerobes • Isolated from most surfaces in mouth • Highest numbers in dental plaque • Do not metabolise carbohydrates – utilise intermediary metabolites (esp. lactate) as energy sources • May play important role in ecology of dental plaque and in aetiology of dental caries

Question 33

gram -ve rods; Facultative/Capnophilic bacteria:

Answer 33

• Haemophilus spp – common in saliva, on epithelial surfaces, and in dental plaque. • Eikenella corrodens – isolated from wide range of oral infections. • Capnocytophaga spp – found in sub-gingival plaque – opportunistic pathogens. • Aggregatibacter (Actinobacillus) actinomycetemcomitans – found in aggressive periodontitis – uncommon in plaque from healthy sites. • Simonsiella – isolated from epithelial surfaces.

Question 34

Gram -ve Rods: obligate anaerobic bacteria

Answer 34

• Comprise a large proportion of the microflora of dental plaque Black-pigmented; Porphyromonas spp (asaccharolytic), Prevotella spp (saccharolytic) Porphyromonas gingivalis • found at subgingival sites (esp. periodontal pockets) highly virulent • produces many putative virulence factors • rarely found in health

Question 35

Prevotella

Answer 35

``` gram -ve • Isolated from dental plaque esp. subgingival sites • Some spp. associated with periodontal disease and abscesses ```

Question 36

Fusobacterium

Answer 36

gram -ve • Asaccharolytic • Certain spp. found in normal gingival crevice and other recovered mainly form periodontal pockets. Other oral Gram-negative anaerobic and microaerophilic bacteria inc Leptotrichia, Campylobacter, Selenomonas, Centipeda

Question 37

Spirochaetes

Answer 37

gram -ve • Numerous in sub-gingival plaque – several morphological types – numbers increase in periodontal disease; role remains unclear Mycoplasma • Pleomorphic bacteria with non-rigid outer membrane – isolated from saliva, oral mucosa and dental plaque

Question 38

Fungi - what candida spp makes up the largest proportion of the oral fungal flora?

Answer 38

C.albicans

Question 39

Viruses

Answer 39

• Herpes Simplex (type I) most common virus detected in the mouth (occasionally detected in the absence of cold sores) • Cytomegalovirus present in the saliva of most individuals • Hepatitis & Human Immunodeficiency Viruses – present in the saliva of asymptomatic individuals • Coxsackie viruses & Papilloma – both groups normally associated with lesions

Question 40

what is the most common virus detected in the mouth;?

Answer 40

Herpes Simplex (type I)

Question 41

what virus is present in the SALIVA of most individuals?

Answer 41

Cytomegalovirus

Question 42

what virus is present in the saliva of | asymptomatic individuals?

Answer 42

Hepatitis & Human Immunodeficiency | Viruses

Question 43

what 2 viruses are normally associates with lesions?

Answer 43

Coxsackie viruses & Papilloma