Streptococci

Question 1

Name 3 species of the mutans streptococcus group

Answer 1

1. S. mutans 2. S. sobrinus 3. S. cricetus

Question 2

Mode of action of mutans streptococcus

Answer 2

They bind to and colonise the tooth surface by producing extracellular polysaccharides (sucrose)

Question 3

Name 3 virulence factors of streptococcus pyogenes required for adherence

Answer 3

1. M protein 2. Fibronectin binding protein (Protein F) 3. Lipoteichoic acid

Question 4

Major causes of infective endocarditis

Answer 4

1. S. sanguinis (32%) 2. S. oralis (30%) 3. S. gordonii (13%)

Question 5

Name some members of the viridans group streptococci Describe their appearance on a CBA.

Answer 5

Streptococcus mutans Streptococcus salivarius Streptococcus sanguinis Streptococcus mitis Green colonies Alpha-haemolytic

Question 6

What does pyrogenic exotoxins cause?

Answer 6

• Scarlet fever - Toxic shock like syndrome (TSLS)

Question 7

Which bacteria is the leading cause of dental caries?

Answer 7

Streptococcus mutans

Question 8

What does GAS bacteria cause? Name one bacteria

Answer 8

Streptococcus pyogenes “Strep” throat Scarlet fever Rheumatic fever Post-streptococcal glomerulonephritis (PSGN) Necrotising fasciitis

Question 9

Antibiotic treatment for GAS?

Answer 9

1. Penicillin (10 day course) 2. Amoxicillin (but narrow spectrum acceptable for children) 3. Erythromycin (for patients sensitive to penicillin) 4. CoAmoxy-Clav Clindamycin (for repeated infections)

Question 10

Where would one expect to find Streptococcus salivarius?

Answer 10

Saliva and tongue; (keratinised surfaces of mouth) Upper respiratory tract; GI tract

Question 11

Name 2 properties of mutans streptococcus

Answer 11

1. Acidogenic - produce acid at a high rate from sugar 2. Aciduric - tolerate high concentrations of acid

Question 12

Where would one expect to find Streptococcus mutans?

Answer 12

On tooth surfaces/fissures

Question 13

Name the group of bacteria that appears to have a “greening” effect on CHOC

Answer 13

Viridans group of streptococcus

Question 14

What test can be carried out to differentiate streptococcus from staphylococcus?

Answer 14

1. Gram stain –> Streptococcus appear as chains; Staphylococcus appear as grape-like clusters 2. Catalase test –> Streptococcus - catalase negative Staphylococcus - catalase positive

Question 15

What can streptococcus anginosus lead to?

Answer 15

Nasty infections: - oral abscesses & brain, liver - bacteraemia & endocarditis - appendicitis & peritontitis

Question 16

Name the bacteria that have ‘beta’ haemolytic activity on CBA

Answer 16

Streptococcus Pyogenes; Streptococcus Anginosus

Question 17

Name a bacteria sensitive to bacitracin

Answer 17

Streptococcus Pyogenes

Question 18

What does M protein serve as?

Answer 18

Major virulence factor for the group A streptococcus. It inhibits the activation of complement and protects the organism from phagocytosis. However, plasma (B) cells generate antibodies against the M protein, which bind to the M protein (opsonization), aiding in the destruction of the organism by macrophages and neutrophils.

Question 19

Name a bacteria sensitive to optochin

Answer 19

Streptococcus Pneumonia

Question 20

Viral pharyngitis VS “Strep Throat”?

Answer 20

Absence of fever and presence of cough in viral pharyngitis

Question 21

Name 5 members of the oralis group of streptococci

Answer 21

1. Streptococcus oralis 2. Streptococcus sanguinis 3. Streptococcus gordonii 4. Streptococcus mitis 5. Streptococcus crista

Question 22

Where would one expect to find Streptococcus anguinosis?

Answer 22

On dental plaque and abscesses

Question 23

Name the bacteria with ‘alpha’ haemolytic activity on CBA

Answer 23

Viridans group of streptococcus; Streptococcus pneumonia

Question 24

Where would one expect to find Streptococcus oralis?

Answer 24

On tooth, forming biofilms

Question 25

Name 3 main types of infections caused by the viridans group of streptococcus

Answer 25

1. Dental infections - caries 2. Endocarditis 3. Abscesses

Question 26

Function of hyaluronic acid capsule in S. pyogenes

Answer 26

Serve as a virulence factor - 1. Evasion of host defences: function as an immunological disguise as it produces hyaluronic acid which is similar to human produced ones, hence reducing phagocytosis 2. Functions in tissue penetration/spread

Question 27

Type of vaccine used against Strep. Pneumonia

Answer 27

Inactivated (Killed) vaccine