M8 - oral streptococci Flashcards
Is staphylococcus catalase + or catalase negative?
catalase positive
Is steptococcus catalase positive or catalase negative?
catalase negative
which group of bacteria isolated from the mouth and can be cultivated from all oral sites?
Oral streptococci
list the four main groups of oral streptococci and the site they are present on
- mutans : tooth surfaces (fissures)
- salivarius - tongue
- anginosus (beta) - plaque
- oralis - tooth biofilm
which microflora produces alpha haemolysis?
oral or viridians streptococci
partial haemolysis
green
most oral streptococci
which microflora produces beta- haemolysis?
S.pyogenes
clear haemolysis on blood agar plates
S.pyogenes
what happens if there is gamma hemolysis? (enterococci)
no hemolysis of blood agar plates
which of the 4 main groups is the only one active in beta heamolysis?
anginosus - dental plaque
which mutans group is the leading cause of tooth decay (dental caries)
streptococcus mutans
- bind and colonise the tooth surface
carbohydrate –> acid –> demineralize enamel
- acidogenic
- aciduric
define acidogenic
produce acid at a high rate from sugar
define aciduric
tolerate high concentrations of acid
list 4 virulence factors
- colonisation
- establishing a biofilm
- acid production
- survival at low pH
how can streptococci mutans colonize on tooth surfaces?
produces water-soluble and insoluble extracellular polysaccharides from sucrose
which significant virulence factor is produced by the oralis group?
IgA protease - protein breakdown avoids immune system
what do S.sanguinis and S.gordonii produce?
extra-cellular soluble and insoluble glucans
which oralis group is most likely to cause bacterial endocarditis?
Strep. sanguinis - acts as a tether for other bacteria
how do S. sanguinis enter the blood system?
after oral trauma eg tooth ectractions
what is no longer recommended by NICE 1 hour before dental treatment?
Prophylaxis antibiotics
which oralis group is very closely related to S.sanguinis but a producer of alpha-amylase rather than IgA protease?
S.gordonii
what does alpha amylase do?
masks bacterial surface antigens and allows the organism to evade the host defences
what does alpa-amylase which is produced by S.gordinii cause?
infective endocarditis
- PadA surface protein interacts with platalets via fibrinogen receptor
what is caused by S.mitis?
bacteraemia, endocarditis and abscesses
which streptococci is similar to S.sanguinis but with tufts of fibrils on surface?
strep. crista
which strep is one of the first bacteria to colonise in the mouth?
salivarius group?
S.salivarius
dominant species in oral cavity throughout life
- isolation; mouth, upper respiratory tract and GI tract
- not normally found in plaque
list an advanatge and disadvantage of the salivarius group?
- Some strains produce bacteriocins ; small antimicrobial peptides
- associated with infections - pharyngitis, tonsilltus
different oral streptococci have different properties and occupy different habitats in the mouth
S.sanguinis, S.mutans - tooth surface
S.salivarius - saliva and tongue
S.mitis - oral epithelia
