L4: The microbial flora of dental plaque Flashcards
what is colonization resistance?
when normal flora acts to exclude pathogens and protect the host
on what sites of the body can microbial colonosation take place?
hard & non-shedding surfaces
tongue crypts have a ____ redox potential
low
what do the low redox potential of tongue crypts mean for gram -ve anaerobes?
acts as a reservoir for gram -ve anaerobes = periodontal disease
____ and ___ _____ of saliva at different oral sites may influence caries susceptibility
flow and ion content
what is the role of glycoproteins in saliva?
- 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
what is the role of urea and free amino acids in saliva?
they are metabolised to lead to an increased pH (counteracts acid production after carb intake)
what is GCF and what does it do?
gingival crevicular fluid; regulates the microflora of the gingival crevice during health and disease
what are the non-specific factors of saliva?
- 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
what are the specific factors in saliva
- 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
stroptococcus is gram ___
+ve
extracellular polysaccharides are associated with
plaque formation
what are the 2 strains present in the streptococcus mutans group?
S.mutans
S.sobrinus
what 2 isolates are present in the aetiology of enamel caries in children and young adults?
dental caries
what are the two main strains of the Streptococcus salivarius group?
• S. salivarius – common isolate from most areas
esp. mucosal surfaces.
• S. vestibularis – isolated mainly from vestibular
mucosa of mouth.
where is s. vestibularis found?
mainly at the vestibular mucosa of the mouth
what are the 3 main strains of the streptococcus milleri group?
S.constellatus, S.intermedius & S.anginosus
what type of pathogens are the streptococcus milleri group? (S.constellatus, S.intermedius & S.anginosus)
Opportunistic pathogens – important cause of
purulent disease
name 2 strains of the streptococcus oralis group?
S.sanguinis, S.gordonii
what type of pathogens are the streptococcus oralis group? (what type of pathogens are the streptococcus milleri group? (S.sanguinis, S.gordonii)
• Opportunistic pathogens – isolated frequently
from infective endocarditis
what type of bacteria is Peptostreptococcus spp (P. anaerobius)
obligate anaerobes
where is Peptostreptococcus spp (P. anaerobius) recovered from?
Recovered from dental plaque esp. in
advanced periodontitis, carious dentine,
infected pulp chambers and root canals, and
dental abscesses.
where is Enterococcus (E.faecalis) recovered from?
Recovered in low nos. from several oral
sites – involved in root canal infections.
where are Staphylococci and micrococci found?
not members of the resident oral microflora – may be present transiently
what is Rothia?
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.
where is Rothia rothia
(Stomatococcus) mucilagenous found?
isolated
from tongue
Actinomyces
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
Eubacterium
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
Lactobacillus
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
Propionibacterium
• Obligate anaerobes – several spp. reported from
mouth incl P. acnes in dental plaque
P. propionicus – opportunistic pathogen &
isolated from actinomycosis
Neisseria
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
Veillonella
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
gram -ve rods; Facultative/Capnophilic bacteria:
• 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.
Gram -ve Rods: obligate anaerobic bacteria
• 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
Prevotella
gram -ve • Isolated from dental plaque esp. subgingival sites • Some spp. associated with periodontal disease and abscesses
Fusobacterium
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
Spirochaetes
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
Fungi - what candida spp makes up the largest proportion of the oral fungal flora?
C.albicans
Viruses
• 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
what is the most common virus detected in the mouth;?
Herpes Simplex (type I)
what virus is present in the SALIVA of most individuals?
Cytomegalovirus
what virus is present in the saliva of
asymptomatic individuals?
Hepatitis & Human Immunodeficiency
Viruses
what 2 viruses are normally associates with lesions?
Coxsackie viruses & Papilloma
