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Flashcards in Streptococcus Deck (67):
0

What does pyogenic mean?

Pus

1

Strep and Staph, which one clusters, which one is in chains?

Strep in chains
Staph in clusters

2

Streptococcus pyogenes

Pharyngitis and skin/soft tissue infections

3

viridans (means green) streptococci

common cause of infective endocarditis

4

streptococcus pneumoniae

pneumonia, upper respiratory infections, meningitis

5

enterococcus faecalis and enterococcus faecium

nosocomial infections

6

Streptococcus gram stain and culture?

Gram positive cocci (spherical)
Arranged in chains or pairs (divides in one plane)

7

streptococcus pneumoniae gram stain and culture

diplococci but can be in chains
lancet-shaped

8

catalase test to distinguish what?

Strep is catalase negative
Staph is catalase positive

9

What do you look at to distinguish between strep types?

Hemolysis patterns

10

Beta strep/hemolysis

Clear zone from complete lysis of RBCs because of production of hemolysins (streptolysin O and streptolysin S)

11

alpha strep/hemolysis

Green zone due to incomplete lysis of RBCs

12

Gamma strep/hemolysis

No hemolysis

13

Strep pyogenes hemolysis pattern?

Beta

14

Strep pneumoniae hemolysis?

alpha

15

How to distinguish between strep pneumoniae and viridans strep?

Strep pneumoniae is bile soluble and inhibited by optochin

16

viridans strep hemolysis?

alpha, green!

17

Besides hemolysis patterns, what is another way to classify strep?

Lancefield classification A-V
Based on antigenic differences in C carbohydrate of cell wall

18

Group A strep is sensitive to bacitracin, whats an example?

strep pyogenes

19

Group B is resistant to bacitracin and hydrolyzes hippurate. Ex?

Strep agalactiae

20

Group D strep hyrolyzes esculin in the presence of bile producing a black pigment. Examples?

Enterococcus grows in high salt
streptococcus bovis does not grow in high salt

21

What is the most important virulence factor for strep pyogenes? What does it do? Is there an antibody for it?

M protein
inhibits opsonization: blocks phagocytosis
Yes but its only strain specific

22

Does strep pyogenes have a capsule? Can antibodies be made against it?

Yes, it is an anti-phagocytic capsule
Antibodies can't be made against it because the capsule is made of hyaluronic acid which is a normal component of the human body

23

2 enzymes made by group A strep (strep pyogenes)

streptokinase - activates plasminogen to form plasmin, which dissolves fibrin in clots
streptolysin O (anti-streptolysin O antibody can be used to diagnose recent group A strep infections which can be important for diagnosing rheumatic fever)

24

What is strep pyogenes erythrogenic toxin? What is it produced by?

causes the rash of scarlet fever
functions as superantigen (polyclonal stimulation of subset of T cells to produce cytokines)
produced only by strains that carry a lysogenic phage

25

There are toxins involved with specific clinical presentations. strep pyrogenic exotoxin A (superantigen) ?

strep toxic shock syndrome

26

There are some toxins involved with specific clinical presentations. Strep pyrogenic exotoxin B?

necrotizing fasciitis

27

Strep pyogenes is normal flora... where?

skin

28

Strep pyogenes can cause 3 types of disease:

1. pyogenic - inflamm produced locally at site where organisms are present (pharyngitis, cellulitis)
2. toxigenic - exotoxin production can cause systemic symptoms at sites where organism is not present (scarlet fever, strep toxic shock syndrome)
3. immunologic - inflamm at sites where there are no organisms (rheumatic fever, acute glomerulonephritis)

29

strep pyogenes is the most common bacterial cause of

sore throat, strep throat

30

throat swab of someone with strep pyogenes doesn't distinguish between normal flora and infection, why?

Some people are carriers but doesn't mean they are sick

31

erysipelas?

strep pyogenes infection involving the skin

32

cellulitis?

strep pyogenes infection involving the skin and superficial fascia

33

necrotizing fasciitis?

strep pyogenes infection affecting the fascia

34

scarlet fever is caused by what and looks like what?

strep pyogenes toxin mediated disease (erythrogenic toxin)
diffuse sand paper rash and sunburn look

35

how do you distinguish strep and staph toxic shock?

strep toxic shock usually has obvious site of soft tissue infection and positive blood cultures

36

What are two presentations of inflammation (at different sites than the original microorganisms) created by a post-strep pyogenes infection?

1. acute glomerulonephritis - immune complex deposition
2. acute rheumatic fever - autoimmune disease caused by cross-reaction of strep M protein antibodies with human antigens in heart, brain, joints

37

acute glomerulonephritis occurs after what? Preventative treatment?

Occurs after skin/soft tissue infection or pharyngitis
No preventative treatment
smoky or rust colored urine

38

Acute rheumatic fever occurs after what? What can it cause? Preventative treatment?

Pharyngitis, not skin/soft tissue infections
Can cause mitral and aortic valve damage
Yes, antibiotics within 9 days of onset of pharyngitis

39

All group A strep are sensitive to what antibiotic?

penicillin G

40

What is the most important virulence factor for strep pneumoniae?

polysaccharide capsule
it is anti-phagocytic like all capsules

41

how many different capsular types of strep pneumoniae?

> 90

42

What do the antibodies against strep pneumoniae do?

opsonize them

43

What is the Quellung reaction?

anti-capsular antibody causes the capsule to swell

44

What percent of adults and children have strep pneumoniae as normal flora in their oropharynx?

5-10% adults
20-40% children

45

What two things can strep pneumoniae also cause?

bacteremia and meningitis

46

How often do people with strep pneumoniae also get bacteremia?

10-20% of cases

47

What does the sputum of a person with strep pneumoniae look like?

purulent - bloody

48

What do people who have had a splenectomy, hyposplenism, and sickle cell disease have in common?

At risk for invasive pneumococcal disease

49

What is a rapid test for strep pneumoniae

Latex agglutination test of CSF

50

When would you use a strep pneumoniae urinary test, what is it looking for?

When you suspect bacteremia
C polysaccharide from cell wall
Its not as sensitive for mild infections

51

How many strains of strep pneumoniae are not fully penicillin susceptible? Why?

5%
Altered penicillin binding protein with decreased binding affinity for penicillin (not inhibited by beta lactamase inhibitor)

52

What are the two vaccines available for strep pneumoniae?

1. polysaccharide vaccine for adults and older children (23 valent)
2. conjugate vaccine for young children (13 valent, conjugated to a carrier protein diphtheria toxoid which stimulates a helper T cell response)

53

Group D streptococcus that grows in high salt

enterococcus

54

Enterococcus is normal flora where?

colon

55

2 main enterococcus pathogens?

E. faecalis - more common, usually not vancomycin resistant
E. faecium - more likely to be resistant to vancomycin

56

vancomycin resistant enterococcus cause what?

nosocomial infections

57

how does enterococcus become resistant to vancomycin?

altered cell well oligopeptide with low affinity for vancomycin so there would be decreased inhibition of peptidoglycan synthesis

58

vancomycin resistant enterococcus is acquired in the hospital. Where does it hang out?

In colons of patients and is transferred to other patients by healthcare workers

59

are vancomycin resistant enterococcus infections usually E. faecium or E. faecalis?

E. faecium

60

Most positive VRE cultures represent what?

Colonization

61

Treatment: penicillin sensitive, penicillin resistant, vancomycin resistant?

penicillin-sensitive: penicillin + aminoglycoside (gentamicin) for synergy
penicillin-resistant: vancomycin
VRE: linezolid or daptom

62

what is a group D streptococcus that doesn't grow in high salt?

streptococcus bovis

63

there is an association with strep bovis bacteremia and endocarditis with what?

colon carcinoma

64

What is a common cause of infective endocarditis?

viridans streptococcus
(endocarditis presents several weeks after a dental procedure)

65

What is strep agalactiae? what group?

Group B
Colonizes genital tract of some women
Causes neonatal meningitis and sepsis and postpartum endometritis

66

Prevention/treatment of strep agalactiae?

Screen with vaginal/rectal cultures at 35-37 weeks of pregnancy
Rapid antigen test
If test is positive, treat with penicillin G at delivery