M8 - oral streptococci

Question 1

Is staphylococcus catalase + or catalase negative?

Answer 1

catalase positive

Question 2

Is steptococcus catalase positive or catalase negative?

Answer 2

catalase negative

Question 3

which group of bacteria isolated from the mouth and can be cultivated from all oral sites?

Answer 3

Oral streptococci

Question 4

list the four main groups of oral streptococci and the site they are present on

Answer 4

• mutans : tooth surfaces (fissures)
• salivarius - tongue
• anginosus (beta) - plaque
• oralis - tooth biofilm

Question 5

which microflora produces alpha haemolysis?

Answer 5

oral or viridians streptococci
partial haemolysis
green
most oral streptococci

Question 6

which microflora produces beta- haemolysis?

Answer 6

S.pyogenes
clear haemolysis on blood agar plates
S.pyogenes

Question 7

what happens if there is gamma hemolysis? (enterococci)

Answer 7

no hemolysis of blood agar plates

Question 8

which of the 4 main groups is the only one active in beta heamolysis?

Answer 8

anginosus - dental plaque

Question 9

which mutans group is the leading cause of tooth decay (dental caries)

Answer 9

streptococcus mutans
- bind and colonise the tooth surface

carbohydrate –> acid –> demineralize enamel

• acidogenic
• aciduric

Question 10

define acidogenic

Answer 10

produce acid at a high rate from sugar

Question 11

define aciduric

Answer 11

tolerate high concentrations of acid

Question 12

list 4 virulence factors

Answer 12

• colonisation
• establishing a biofilm
• acid production
• survival at low pH

Question 13

how can streptococci mutans colonize on tooth surfaces?

Answer 13

produces water-soluble and insoluble extracellular polysaccharides from sucrose

Question 14

which significant virulence factor is produced by the oralis group?

Answer 14

IgA protease - protein breakdown avoids immune system

Question 15

what do S.sanguinis and S.gordonii produce?

Answer 15

extra-cellular soluble and insoluble glucans

Question 16

which oralis group is most likely to cause bacterial endocarditis?

Answer 16

Strep. sanguinis - acts as a tether for other bacteria

Question 17

how do S. sanguinis enter the blood system?

Answer 17

after oral trauma eg tooth ectractions

Question 18

what is no longer recommended by NICE 1 hour before dental treatment?

Answer 18

Prophylaxis antibiotics

Question 19

which oralis group is very closely related to S.sanguinis but a producer of alpha-amylase rather than IgA protease?

Answer 19

S.gordonii

Question 20

what does alpha amylase do?

Answer 20

masks bacterial surface antigens and allows the organism to evade the host defences

Question 21

what does alpa-amylase which is produced by S.gordinii cause?

Answer 21

infective endocarditis

- PadA surface protein interacts with platalets via fibrinogen receptor

Question 22

what is caused by S.mitis?

Answer 22

bacteraemia, endocarditis and abscesses

Question 23

which streptococci is similar to S.sanguinis but with tufts of fibrils on surface?

Answer 23

strep. crista

Question 24

which strep is one of the first bacteria to colonise in the mouth?

Answer 24

salivarius group?

Question 25

S.salivarius

Answer 25

dominant species in oral cavity throughout life

• isolation; mouth, upper respiratory tract and GI tract
• not normally found in plaque

Question 26

list an advanatge and disadvantage of the salivarius group?

Answer 26

• Some strains produce bacteriocins ; small antimicrobial peptides
• associated with infections - pharyngitis, tonsilltus

Question 27

different oral streptococci have different properties and occupy different habitats in the mouth

Answer 27

S.sanguinis, S.mutans - tooth surface
S.salivarius - saliva and tongue
S.mitis - oral epithelia