13. Streptococci

Question 1

Development of post streptococcal glomerulonephritis is due to what mechanism?

Answer 1

Cross-reaction of host antibodies against Streptococcus pyogenes

Question 2

Which streptococci is a recognised cause of disease in neonates?

Answer 2

Agalactiae

Question 3

Which streptococci is commonly associated with abscess formation?

Answer 3

Aginosus

Question 4

Which streptococci is identified in the microbiology lab by its susceptibility to optochin?

Answer 4

Pneumoniae

Question 5

What is the appearance of streptococci with gram staining?

Answer 5

Gram positive cocci in chains or pairs

Question 6

What agar is optimal for streptococci?

Answer 6

Blood supplemented

Question 7

How are streptococci grouped based on blood haemolysis?

Answer 7

a= partial haemolysis, turns blood agar green
b= total lysis
y= no lysis

Question 8

Which Lancefield group is the only one which is not beta haemolytic?

Answer 8

Group D

Question 9

How are streptococci differentiated from staphylococci?

Answer 9

Strep are catalase negative

Question 10

What decides the Lancefield group of a strep?

Answer 10

Antigen present on the cell wall

Question 11

Name the b haemolytic streps

Answer 11

Pyogenes
Agalactiae
Group C and G

Question 12

What Lancefield group is strep pyogenes?

Answer 12

A

Question 13

Where do pyogenes colonise?

Answer 13

Oropharynx of children and young adults

Question 14

How is pyogenes transmitted?

Answer 14

Droplets

Question 15

What are the main virulence factors of strep pyogenes?

Answer 15

M proteins
M-like proteins
Capsule
Hyaluronidase
Streptolysin
Pyogenic exotoxin
Haemolysins
Streptokinase

Question 16

What is the function of M proteins?

Answer 16

Attach to cells

Prevent phagocytosis

Question 17

What is the function of M-like proteins?

Answer 17

Prevent oponisation

Question 18

What is the function of streptolysin?

Answer 18

Lysis of neutrophils, platelets and organelles

Question 19

What is the function of pyogenic exotoxin?

Answer 19

superantigen which causes rash and fever

Question 20

Name the infections that can be caused by strep pyogenes

Answer 20

Pharyngitis
Scarlet fever
Impetigo
Erysipelas
cellulitis
Necrotising fasciitis
TSS
BSI
Puerperal sepsis
Burns infections

Question 21

Describe the rash present in scarlet fever

Answer 21

Blanches

Sandpaper feel

Question 22

What is the difference between erysipelas and cellulitis?

Answer 22

Erysipelas involves upper dermis and superficial lymphatics

Cellulitis involves deeper dermis and subcutaneous fat

Question 23

What are the 2 post infectious immune-mediated complications caused by a strep pyogenes infection?

Answer 23

Rheumatic fever

Glomerulonephritis

Question 24

What type of hypersensitivity reaction causes rheumatic fever?

Answer 24

Type 2

Antibodies cross-react with cardiac tissue

Question 25

What is the name of the criteria used to diagnose rheumatic fever?

Answer 25

Jones criteria

Question 26

What type of hypersensitivity reaction causes glomerulonephritis?

Answer 26

Type 3 | Immune complexes are deposited on glomerular basement membrane

Question 27

What Lancefield group is strep agalactiae?

Answer 27

B

Question 28

Where does strep agalactiae colonise?

Answer 28

Lower GI and genitourinary tract

Question 29

What infection is caused by strep agalactiae?

Answer 29

Neonatal sepsis

Question 30

What infections are caused by group C b haemolytic strep?

Answer 30

Tonsilitis | Wound sepsis

Question 31

What infections are caused by group G b haemolytic strep?

Answer 31

Upper RTI | Endocarditis

Question 32

Name the a haemolytic strep

Answer 32

Viridans | Pneumoniae

Question 33

Where does strep viridans colonise?

Answer 33

Oropharynx GIT Genitourinary tract

Question 34

What diseases are caused by strep viridans?

Answer 34

Dental carries Endocarditis Brain lesions

Question 35

How is spread of strep pneumoniae prevented?

Answer 35

Vaccine is available

Question 36

Where does strep pneumoniae colonise?

Answer 36

Oropharynx

Question 37

How does strep pneumoniae spread?

Answer 37

Droplet

Question 38

What infections are caused by strep pneumoniae?

Answer 38

Pneumonia Sinusitis and otitis media Meningitis BSI

Question 39

What are the main virulence factors of strep pneumoniae?

Answer 39

Pneumolysin | Capsule

Question 40

What are the risk factors for strep pneumoniae infection?

Answer 40

``` Influenza Splenectomy COPD, asthma Immunocompromised Smoking and alcohol ```

Question 41

What class of drugs is pneumoniae becoming resistant to?

Answer 41

Penicillins | Can alter the structure of penicillin binding protein

Question 42

Where are enterococci found?

Answer 42

Bowel flora

Question 43

What are the lab results for enterococci?

Answer 43

Faculative anaerobes a or b haemolytic Grow on MacConkey agar

Question 44

What does VRE stand for?

Answer 44

Vancomycin resistant enterococci

Question 45

What infections are caused by enterococci?

Answer 45

UTI Wound and intra-abdominal Endocarditis BSI

Question 46

What class of antibiotics are enterococci intrinsically resistant to?

Answer 46

Cephalosporins

Question 47

What are the antibiotics of choice for enterococci?

Answer 47

Amoxicillin Vancomycin Linezolid

Question 48

How is a past group A strep infection detected?

Answer 48

ASO (antibodies to streptolysin O) titre serology test

Question 49

What susceptibility test is used to show a bacteria is strep pneumoniae?

Answer 49

Optochin: pneumoniae are susceptible

Question 50

How do enterococci appear on MacConkey agar?

Answer 50

Small, magenta coloured colonies