Streptococcae

Question 1

Role of the catalase test

Answer 1

Streptococcae are catalase negative (unlike enterococcus) - they can’t convert hydrogen peroxide to water and oxygen

Question 2

Role of blood agar test

Answer 2

Can be subcategorised into beta (complete haemolysis), alpha (partial haemolysis -green) and gamma (non-haemolytic)

Question 3

Main types of beta haemolytic streptococae

Answer 3

Lancefield groups A (pyogenes) and B (agalactia)

Question 4

What is the purpose of the Lancefield grouping?

Answer 4

To differentiate between beta haemolytic streptococcae i.e. group A and group B, based on their ability to agglutinate

Question 5

What is another name for group A strep?

Answer 5

Streptococcus pyogenes

Question 6

What is another name for group B strep?

Answer 6

Streptoccus agalactia

Question 7

What is another name for streptococcus agalactia?

Answer 7

Group B strep

Question 8

What is another name for streptoccus pyogenes?

Answer 8

Group A strep

Question 9

What is the difference between type 1 and 2 necrotising fasciitis?

Answer 9

Type 1 = polymicrobial (streptococcus, staphylococcus, enterobacteriae
Type 2 = caused by group A strep (streptococcus pyogenes)

Question 10

What causes toxic shock syndrome?

Answer 10

Streptococcus pyogenes (group A strep) - predominately caused by the exotoxins A and C which cause endothelial damage and fever

Question 11

What causes scarlet fever?

Answer 11

Group A streptococcus (streptoccus pyogenes)

Question 12

Normal habitat of group A strep

Answer 12

Oropharynx

Question 13

Normal habitat of group B strep

Answer 13

GI tract, female genital tract (30% of women are carriers)

Question 14

What percentage of women are GBS carriers?

Answer 14

20-40% (but carriage is intermittent), occurs more frequently in black African ethnic groups

Question 15

Which streptococci fall into the alpha haemolytic group?

Answer 15

Partial haemolysis = Enterococcus, strep pneumonia, strep viridans

Question 16

How is “early onset” neonatal GBS infection defined?

Answer 16

Within 7 days of delivery

Question 17

Risk of recurrent GBS carriage for a mother who has previously GBS detected in another pregnancy

Answer 17

50% will experience recurrence

Question 18

When should GBS treatment be given during pregnancy?

Answer 18

If the patient has a GBS positive UTI. Not if they have a positive vaginal or rectal swab.

Question 19

Recommended management for a patient who is known GBS positive who ruptures their membranes at term

Answer 19

Give intrapartum antibiotic prophylaxis and induce labour

Question 20

What should be given to a patient if she requires intrapartum antibiotic prophylaxis but is allergic to penicillin?

Answer 20

If mild allergy - give clindamycin or a cephalosporin

If severe allergy- give vancomycin

Question 21

Rate of neonatal GBS disease

Answer 21

5 in 10,000 births

Question 22

How does streptococcus pneumoniae appear on blood agar?

Answer 22

Partial haemolysis (alpha haemolytic group)-green ring around the colony

Question 23

How does streptococcus pneumoniae appear under the microscope?

Answer 23

diplococcus- “draughtsman shaped colonies”

Question 24

Which streptococcus species is described as forming “draughtsman shaped” colonies

Answer 24

Streptoccocus pneumoniae

Question 25

What is the role of optochin in differentiating species of streptococcus?

Answer 25

Streptococcus is sensitive to optochin, unlike other streptococcus species in the alpha haemolytic group

Question 26

What is the role of aesculin in differentiating species of streptococcus?

Answer 26

Derived from horsechesnut, when hydrolysed, it forms a dark brown ring. Enterococcus (both alpha haemolytic and gamma haemolytic strains) are aesculin positive

Question 27

optochin sensitive, bile soluble streptococcus

Answer 27

Streptococcus pneumonia

Question 28

optochin resistant, bile insoluble streptococcus

Answer 28

Streptococcus viridans

Question 29

aesculin positive streptococcus

Answer 29

Enterococcus

Question 30

Which gram positive bacteria are catalase positive?

Answer 30

Staph aureus and enterococcus

Question 31

Group F streptococcae (name and disease)

Answer 31

Streptococcus anginosus, forms Liver abscesses