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FIM > 13. Streptococci > Flashcards

13. Streptococci Flashcards

1
Q

Development of post streptococcal glomerulonephritis is due to what mechanism?

A

Cross-reaction of host antibodies against Streptococcus pyogenes

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2
Q

Which streptococci is a recognised cause of disease in neonates?

A

Agalactiae

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3
Q

Which streptococci is commonly associated with abscess formation?

A

Aginosus

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4
Q

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

A

Pneumoniae

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5
Q

What is the appearance of streptococci with gram staining?

A

Gram positive cocci in chains or pairs

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6
Q

What agar is optimal for streptococci?

A

Blood supplemented

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7
Q

How are streptococci grouped based on blood haemolysis?

A 
a= partial haemolysis, turns blood agar green
b= total lysis
y= no lysis
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8
Q

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

A

Group D

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9
Q

How are streptococci differentiated from staphylococci?

A

Strep are catalase negative

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10
Q

What decides the Lancefield group of a strep?

A

Antigen present on the cell wall

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11
Q

Name the b haemolytic streps

A

Pyogenes
Agalactiae
Group C and G

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12
Q

What Lancefield group is strep pyogenes?

A

A

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13
Q

Where do pyogenes colonise?

A

Oropharynx of children and young adults

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14
Q

How is pyogenes transmitted?

A

Droplets

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15
Q

What are the main virulence factors of strep pyogenes?

A 
M proteins
M-like proteins
Capsule
Hyaluronidase
Streptolysin
Pyogenic exotoxin
Haemolysins
Streptokinase
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16
Q

What is the function of M proteins?

A

Attach to cells

Prevent phagocytosis

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17
Q

What is the function of M-like proteins?

A

Prevent oponisation

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18
Q

What is the function of streptolysin?

A

Lysis of neutrophils, platelets and organelles

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19
Q

What is the function of pyogenic exotoxin?

A

superantigen which causes rash and fever

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20
Q

Name the infections that can be caused by strep pyogenes

A 
Pharyngitis
Scarlet fever
Impetigo
Erysipelas
cellulitis
Necrotising fasciitis
TSS
BSI
Puerperal sepsis
Burns infections
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21
Q

Describe the rash present in scarlet fever

A

Blanches

Sandpaper feel

22
Q

What is the difference between erysipelas and cellulitis?

A

Erysipelas involves upper dermis and superficial lymphatics

Cellulitis involves deeper dermis and subcutaneous fat

23
Q

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

A

Rheumatic fever

Glomerulonephritis

24
Q

What type of hypersensitivity reaction causes rheumatic fever?

A

Type 2

Antibodies cross-react with cardiac tissue

25
Q

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

A

Jones criteria

26
Q

What type of hypersensitivity reaction causes glomerulonephritis?

A

Type 3

Immune complexes are deposited on glomerular basement membrane

27
Q

What Lancefield group is strep agalactiae?

A

B

28
Q

Where does strep agalactiae colonise?

A

Lower GI and genitourinary tract

29
Q

What infection is caused by strep agalactiae?

A

Neonatal sepsis

30
Q

What infections are caused by group C b haemolytic strep?

A

Tonsilitis

Wound sepsis

31
Q

What infections are caused by group G b haemolytic strep?

A

Upper RTI

Endocarditis

32
Q

Name the a haemolytic strep

A

Viridans

Pneumoniae

33
Q

Where does strep viridans colonise?

A

Oropharynx
GIT
Genitourinary tract

34
Q

What diseases are caused by strep viridans?

A

Dental carries
Endocarditis
Brain lesions

35
Q

How is spread of strep pneumoniae prevented?

A

Vaccine is available

36
Q

Where does strep pneumoniae colonise?

A

Oropharynx

37
Q

How does strep pneumoniae spread?

A

Droplet

38
Q

What infections are caused by strep pneumoniae?

A

Pneumonia
Sinusitis and otitis media
Meningitis
BSI

39
Q

What are the main virulence factors of strep pneumoniae?

A

Pneumolysin

Capsule

40
Q

What are the risk factors for strep pneumoniae infection?

A 
Influenza
Splenectomy
COPD, asthma
Immunocompromised
Smoking and alcohol
41
Q

What class of drugs is pneumoniae becoming resistant to?

A

Penicillins

Can alter the structure of penicillin binding protein

42
Q

Where are enterococci found?

A

Bowel flora

43
Q

What are the lab results for enterococci?

A

Faculative anaerobes
a or b haemolytic
Grow on MacConkey agar

44
Q

What does VRE stand for?

A

Vancomycin resistant enterococci

45
Q

What infections are caused by enterococci?

A

UTI
Wound and intra-abdominal
Endocarditis
BSI

46
Q

What class of antibiotics are enterococci intrinsically resistant to?

A

Cephalosporins

47
Q

What are the antibiotics of choice for enterococci?

A

Amoxicillin
Vancomycin
Linezolid

48
Q

How is a past group A strep infection detected?

A

ASO (antibodies to streptolysin O) titre serology test

49
Q

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

A

Optochin: pneumoniae are susceptible

50
Q

How do enterococci appear on MacConkey agar?

A

Small, magenta coloured colonies

FIM (44 decks)

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