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Pathophysiology > Streptococci and Enterococci > Flashcards

Streptococci and Enterococci Flashcards

1
Q

What are 2 key features of Streptococci?

A

1) catalase NEG

2) cocci in pairs and chaines (strep is a strip)

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2
Q

________ are aerobic while _____________ are anaerobic

A

staph (aero)

strep (anaero)

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3
Q

How do you know if an organism is catalase positive or negative?

A

catalase positive - O2 bubbles up

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4
Q

What are the 3 hemolytic properties of strep?

A

1) COMPLETE hemolysis (beta)
2) incomplete hemolysis (alpha)
3) NO hymolysis (gamma)

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5
Q

What is the important strep species of Group A?

A

streptococcus pyogenes

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6
Q

What is the important strep species of Group B?

A

streptococcus agalactiae

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7
Q

What kind of infections are associated with S. pyogenes?

A

1) ACUTE PHARYNGITIS (resp droplets, 5-15 year old with fever, sore throat, headache, swollen lymph nodes)
2) IMPETIGO (2-5 child with localized skin disease)
3) ERYSIPELAS (spreading erythema with well demarcated edge on face or legs, fever and lymphadenopathy)
4) SCARLET FEVER
5) NEC FASC

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8
Q

What are 7 clinical manifestations of strep pyogenes infection?

A

1) Acute pharyngitis
2) Impetigo
3) Erysipelas
4) Scarlet fever
5) Nec fas
6) Toxic shock-like syndrome
7) Puerperal sepsis

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9
Q

What two bacteria can cause toxic shock?

A

staph and strep (group A)

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10
Q

Which toxic shock like syndrome toxins belong to staph? strep?

A 
staph = TSST-1
strep = SPE
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11
Q

What patient population do you see puerperal sepsis?

A

women following delivery

bacteria from genital tract or obstetric personnel invade upper genital tract

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12
Q

What are dangerous sequelae after strep?

A

Rheumatic fever (1-5 weeks after)

Acute glomerulonephritis (antigen+antibody+C deposited in glomeruli)

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13
Q

Why can rheumatic fever be dangerous?

A

cardiac lesions called Aschoff bodies and vascular damage leads to possible endocarditis later in life

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14
Q

What are 4 accomplishments of group A strep that help promote virulence?

A
  1. adhere to surface of host cells
  2. invade epithelial cells
  3. avoid opsonization/phagocytosis
  4. produce variety of toxins/enzymes
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15
Q

What are the 7 S. pyogenes virulence factors?

A 
Capsular polysaccharide
lipoteichoic acid
hemolysins
streptokinase
hyaluronidase
nuclease
C5a peptidase
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16
Q

What are the 2 hemolysins of S. pyogenes?

A 
Streptolysin S (oxygen stable, non-antigenic)
Streptolysin O (oxygen labile, ASO antibodies)
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17
Q

What is SPE?

A

streptococcal pyrogenic exotoxins

superantigens of s. pyogenes; stimulate cytokine response leading to shock
responsible for rash in scarlet fever (erythrogenic exotoxin)

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18
Q

What protein is absolutely required for the pathogenesis of s. pyogenes?

A

M protein

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19
Q

What does the M protein do?

A
  • binds to epidermal cells
  • allows bacteria to survive
  • antiphagocytic
  • degrades complement C3b
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20
Q

What 2 proteins of s. pyogenes allows for spread of bacteria in tissues?

A

streptolysins

streptokinase

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21
Q

True or false: there are antibiotic resistant strep pyogenes?

A

FALSE

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22
Q

What drugs do you use to treat s. pyogenes?

A

penicillin/ampicillin/amoxacillin

cephalosporins

erythromycin (for pen allergic patient)

23
Q

What does strep agalactiae cause?

A
  • neonatal pneumonia, sepsis, meningitis
  • skin/wound infections in adult diabetic patients
  • endocarditis
24
Q

Is strep agalactiae normal on the body anywhere?

A

throat, vaginal and GI tract

25
Q

How can baby get GBS (group b strep)?

A

normal maternal colonization of vagina or rectum exposes baby at delivery

leads to meningitis, bacteremia, pneumoniae

26
Q

How do you prevent babies from getting GBS at delivery?

A

culture mom at 35-37 weeks and treat mom as if she is positive

27
Q

How do you treat GBS?

A

penicillin/ampicillin

gentamicin to enhance killing

clindamycin for pen allergic

28
Q

Aside from s. pyogenes and s. agalactiae, what are the other beta hemolytic strep?

A 
Group C (vet infections, pharyngitis in college kids, sepsis)
Group F (abscesses)
Group G (pharyngitis, sepsis in neonates)
29
Q

How do you diagnose GBS?

A

antigen test
culture
identification
antibody detection (ASO, Anti-DNase)

30
Q

True or false: if GBS strep test comes up negative, pt is negative

A

FALSE; always do a back up culture

31
Q

What are Viridans Streptococci?

A

alpha or gamma hemolytic (NO BETA)
major cause of dental caries
important cause of endocarditis
causes sepsis in neutropenic cancer patient

32
Q

What are the 5 groups of viridans strep?

A
  • sanguis
  • mitis
  • mutans
  • salivarius
  • bovis
33
Q

What is included in the bovis group? What does it cause?

A

non-enterococcal group D strep

bacteremia, meningits, endocarditis

34
Q

Isolation of s. bovis from blood is associated with what?

A

carcinoma of colon

35
Q

What bacteria has butterscotch scent on agar plates? also requires CO2 for isolation and makes pinpoint colonies

A

strep milleri

36
Q

Where are strep milleri infections usually found?

A

brain absecesses

cause pyogenic infections of cardiac, abdominal, skin and CNS tissues

37
Q

Where is strep milleri usually found?

A

mouth, oropharynx, GI tract, vagina

38
Q

Where is strep pneumoniae usually found?

A

upper resp tract

39
Q

What can strep pneumo cause?

A
  • pneumonia
  • paranasal sinusitis
  • otitis media
  • meningitis
  • osteomyelitis
  • septic arthritis
  • endocarditis
  • peritonitis
  • cellulitis
40
Q

For which bug is a polysaccharide capsule important virulence factor?

A

strep pneumoniae

41
Q

Name the 5 virulence factors of strep pneumoniae

A
  • pneumolysin
  • neuraminidase
  • phosphorylcholine
  • sIgA protease
  • Teichoic acid/peptidoglycan
42
Q

What does sIgA protease do?

A

prevent IgA mediated binding of pneumococcal cells to mucus

43
Q

What does teichoic acid/peptidoglycan do?

A

activates complement by alt pathway –> mediates inflammation

44
Q

What is the most common cause of CA acute bacterial pneumonia? Also most common cause of bacterial meningitis

A

s. pneumoniae

45
Q

What is responsible for the highest rate of meningitis in kids under 2?

A

s. pneumoniae

46
Q

What does s. pneumoniae look like?

A

gram+
lancet shaped cocci
diplococci

47
Q

What does s. pneumoniae look like on blood agar?

A

dimes, alpha hemolytic

48
Q

What inhibits s. pneumoniae growth in the lab?

A

optochin

49
Q

How do you decide how to treat strep pneumococcal infections?

A

look at MIC for susceptibility

50
Q

What 3 drugs can you give for susceptible pneumococcal infections?

A

penicillin
cefotaxime
ceftriaxone

51
Q

What are some characteristics of enteroccus?

A 
gram+ 
pairs
short chains
group D
PYR pos
a, B, y hemolytic
52
Q

What are the 2 classes of entercoccus virulence factors?

A

1) colonization
- aggregation substance
- carbohydrate adhesins
2) secreted
- cytolysin
- pheromone
- gelatinase

53
Q

true or false: there are some vancomycin resistant enterococci

A

TRUE (E. faecium)

Van A - plasmid mediated
Van B - chromosomal
Van C - intrinsic

Makes YELLOW colonies

54
Q

What are enterococcal infections intrinsically resistant to?

A

all cephalosporins, trimetoprim-sulfa, aminoglycosides

Pathophysiology (26 decks)

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