Streptococci Flashcards

1
Q

The three most important human pathogens

A

Strep pyogenes (A), Strep agalactiae (B), Strep pnumonia

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2
Q

Are Strep facultative anaerobes?

A

Yes

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3
Q

What color is Alpha hemolysis on a blood agar plate?

A

Green

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4
Q

What color is Beta Hemolysis

A

Clear

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5
Q

What about gamma hemolysis?

A

This is almost non-hemolytic.

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6
Q

What hemolysis pattern do AN and B follow?

A

Beta hemolytic

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7
Q

S. pneumoniae?

A

Alpha hemolytic

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8
Q

Catalase negative or positive?

A

Negative…this differentiates them from staph

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9
Q

Oxidase negative or positive?

A

Negative

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10
Q

What is the largest Strep A burden in the world?

A

Acute Rheumatic Fever which follows pharyngitis. Can lead to Rheumatic heart disease.

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11
Q

Acute glomerulonephrits is a sequela of strep that follows what type of infections

A

Skin infections generally

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12
Q

ARF and AGN are immune mediated diseases?

A

Yes

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13
Q

Beta hemolysis due to what enzymes?

A

Streptolysin O and streptolysin S

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14
Q

Streptolysin S is oxygen stable

A

true

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15
Q

SLO is oxygen stable

A

False. SLO is oxygen unstable so you have to grow it below the surface of the agar to see its activity

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16
Q

Group A virulence factors

A

Hyaluronic acid capsule
M Protein
Lipoteichoic acid

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17
Q

What is significant about the hyaluronic acid capsule

A

It is antiphagocytic and the structure of the hyaluronic acid is identical to the structure of human hyaluronic acid meaning that there are no antibodies formed against it

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18
Q

M protein significance?

A

Binds to fibronectin and other host proteins which hides the bacteria from the immune system and makes it antiphagocytic. It is the serological marker for Group A strep.

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19
Q

LTA?

A

adhesin, PAMP, and defense against antimicrobial peptides

20
Q

What are streptococcal pyrogenic exotoxin A?

A

Superantigens…massively activate the immune system and create cytokine storms leading to sepsis

21
Q

Treatment of Streptococcal pharyngitis with penicillin reduces the risk of

A

ARF

22
Q

Can you get strep throat from strains with identical M proteins more than once?

A

Nope. You develop a type specific M- antibody to protect against the recurrence of infection with the infecting serotype.

23
Q

Puerperal fever?

A

streptococcal infection that frequently developed after giving birth.

24
Q

Group A strep Impetigo

A

superficial purulent skin infection
Most common in children
Often follows insect bites
weeping vesicles that form honey colored crust

25
Q

What can a GAS skin infection like Impetigo turn into?

A

Glomerulonephritis

26
Q

What is Ecthyma

A

deep impetigo…pus filled center.

27
Q

erysipelas

A

a form of streptococcal cellulitis, charactertized by red erythema, edema, pain, fever, lymphadenopathy

28
Q

Cellulitis

A

Acute inflammatory condition of the skin. Deeper than ecthyma or erysipelas. Pain edema, swelling, heat,

29
Q

Streptococcal toxic shock and necrotizing fascitis

A

Infection begins inside. Just looks like a bruise, Rapid necrosis of up to an inch an hour. Flu-like, edema, extreme pain way out of proportion to the lesion appearance

30
Q

Major virulence factors in necrotizing fascitis?

A

Streptococcal pyrogenic exotoxins.

31
Q

Treatment of NF?

A

Rapid antibiotic treatment with penacillin or clindamycin if they have a penicillin allergy

32
Q

Streptococcal toxic shock presentation

A

Shock, sepsis, rash that blanches when pressure is applied. Not as common as staph aureus tss

33
Q

Clinical diagnosis of group A strep toxic shock syndrome

A
Isolation of GAS from a clinically significant specimen and two or more of the following:
renal impairment
coagulopathy
Liver dysfunction
Acute respiratory distress
macular rash
soft tissue necrosis
34
Q

Erythema marginatum

A

skin rash that is a sign of ARF

35
Q

Subcutaneous nodules

A

Also a sign of ARF

36
Q

AGN findings

A

edema, hypertension, hematuria, proteinuria, malaise, headache, back pain
Lab: Ig, C3

37
Q

Group B strep

A

Beta hemolysis

Bile esculin synthesis, Bacitracin resistant…the 3 Bs

38
Q

What is CAMP factor

A

A factor produced by Group B strep that synergizes with staph aureus hemolysin to create increased lysis of red cells

39
Q

Group B strep used to be the predominant cause of what in infants?

A

septicemia and meningitis in infants

40
Q

What is a sensitive test for Group B strep>

A

Bile Esculin Hydrolysis

41
Q

CAMP test

A

You cross streak a potential GBS sample with staph aureus and look to see if its Beta Hydrolysis ring expands. Will separate GBS from GAS.

42
Q

GBS virulent factor

A

Capsule…antiphagocytic of course

43
Q

Adheisns

A

Alpha protein and fibrinogen binding proteins

44
Q

Early onset GBS infection in neonates falls during what time period?

A

7 days or younger.

Includes septicemia, resp distress, meningitis

45
Q

Late onset GBS in infants when?

A

2 weeks to 2 months

46
Q

Viridans streptococci

A

oral strep, alpha hemolytic

distinguished from enterococci by inabiltiy to grow in 6.5 % nacl