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Bacteriology > Streptococci and Enterococci > Flashcards

Streptococci and Enterococci Flashcards

1
Q

Are Streptococci catalase positive or negative?

A

Negative

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2
Q

What do Streptococci look like microscopically?

A

Gram positive cocci in pairs and chains

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3
Q

What are the different classifications of Strep based on hemolysis?

A 
Beta-hemolytic = complete hemolysis
Alpha-hemolytic = partial
Gamma-hemolytic = non-hemolytic
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4
Q

What is the major species of Beta-hemolytic Group A streptococci?

A

Strep pyogenes

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5
Q

What is the major species of Beta-hemolytic Group B streptococci?

A

Strep agalactiae

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6
Q

What are virulence factors of Group A beta-hemolytic Strep?

A
  • M protein
  • Capsule
  • Surface adhesins
  • Toxins (hemolysins, SpeA,B,C)
  • Enzymes (DNAses, hyaluronidase, streptokinase)
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7
Q

What is M protein?

A
  • Antiphagocytic
  • Binds serum proteins (e.g. Factor H) that inhibit activation of alternative complement components
  • Elicits opsonic antibodies
  • Adhesive
  • Generates antibodies that react with cardiac myosin and sarcolemma (–> rheumatic heart disease)
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8
Q

What toxins are secreted by Group A Strep?

A

Hemolysins

  • Streptolysin O (antibodies to this suggest previous infection)
  • Streptolysin S

Streptococcal Pyrogenic Exotoxins (Spe)
- SpeA, Spe B, Spe C

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9
Q

What causes scarlet fever?

A

Spe A and Spe C (streptococcal pyrogenic exotoxins)

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10
Q

What causes Strep toxic shock syndrome?

A

Spe A and Spe C (streptococcal pyrogenic exotoxins)

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11
Q

What is the function of streptokinase?

A

Degrades fibrin
Used as a medication to break down large clots and restore blood flow, but must be used in very careful and controlled setting

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12
Q

What are suppurative (involving pus) diseases caused by Strep pyogenes (Group A beta-hemolytic strep)?

A 
Pharyngitis
- Scarlet fever
Impetigo
Erysipelas
Cellulitis with lymphangitis
Necrotizing fasciitis
Streptococcal toxic shock syndrome
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13
Q

What are signs of bacterial pharyngitis?

A

No cough differentiates from viral a lot of the time
Fever
Purulent exudate
Cervical lymphadenopathy

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14
Q

Do rapid antigen tests have better specificity or sensitivity?

A

Better specificity.

Not as good sensitivity (false negatives)

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15
Q

What is the treatment of choice for Group A beta-hemolytic pharyngitis (strep throat)?

A

Penicillin

if penicillin allergy, use macrolides (azithro, clarithro, erythro) or clindamycin

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16
Q

What are symptoms of scarlet fever?

A

Rash on trunk
Strawberry tongue
Desquamation of skin

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17
Q

What is the treatment for impetigo?

A

Topical: bacitracin, mupirocin
Systemic: amoxicillin-clavulanic acid or cephalexin

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18
Q

What organisms can cause impetigo?

A

Group A Strep and Staph aureus

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19
Q

What is erysipelas?

A

Form of cellulitis, bright erythema, edema, sharp raised edges

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20
Q

What organisms can cause erysipelas?

A

High characteristic of beta-hemolytic Strep

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21
Q

What disorder do these clinical clues suggest:

  • Pain out of proportion for clinical findings
  • Septic shock in association with cellulitis
  • Hemorrhagic bullae
A

Necrotizing fasciitis

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22
Q

What is the mechanism by which rheumatic fever/rheumatic heart disease develops?

A

Molecular mimicry - certain M proteins have epitopes shared with cardiac antigens
- T lymphocytes enter heart tissue –> inflammatory cytokines –> cardiac lesions

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23
Q

What is the mechanism by which acute glomerulonephritis develops from Strep?

A

Deposition of immune complexes

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24
Q

What are the clinical criteria necessary to diagnose rheumatic fever?

A

2 major criteria OR 1 major plus 2 minor criteria
Major: polyarithritis, carditis, chorea, erythema marginatum, subcutaneous nodules
Minor: arthralgia, fever, elevated C-reactive protein, 1st degree heart block

25
Q

What population is at highest risk for Group B Strep?

A

Neonates (can acquire in utero, at birth, or first month of life)

26
Q

What is treatment for Group B Strep?

A

Penicillin

- Need to screen all pregnant women and treat colonized women at term

27
Q

What larger taxonomic group does Strep anginosis fall in?

A

Strep milleri

28
Q

What are common clinical manifestations of Strep anginosis infection?

A

Cause abscesses (liver, brain, peridontal)

29
Q

Is Strep anginosis alpha, beta, or gamma hemolytic?

A

Trick question! Can be all three

30
Q

Are Viridans Strep alpha, beta, or gamma hemolytic?

A

Alpha and gamma

31
Q

What clinical test/exam must be performed when a patient tests positive for Strep bovis?

A

Colonoscopy

S. bovis is associated with colonic neoplasia

32
Q

What are common clinical manifestations of Viridans strep?

A

Endocarditis
Bacteremia
Abscesses
(really is only a problem if it gets into blood stream)

33
Q

What is treatment for Viridans strep?

A

Penicillin or vancomycin (if resistant to penicillin)

34
Q

What are the two major Enterococcus species?

A

E. faecalis, E. faecium

35
Q

Is Strep pneumoniae alpha, beta, or gamma hemolytic?

A

Alpha hemolytic

36
Q

How can we differentiate Strep pneumoniae from other alpha hemolytic Strep (like Viridans strep)?

A

Optochin disk on blood agar plate - Strep pneumo is susceptible

37
Q

What are the virulence factors of Strep pneumoniae?

A
  • Evades host immunity (capsule, pneumolysin)
  • Adheres to host surfaces (phosphocholine, surface adhesion proteins)
  • Produces very few toxins
38
Q

What may often precede a Strep pneumoniae infection?

A

Viral infection

39
Q

What are risk factors for Strep pneumoniae infection?

A
  • Lack of pneumococcal vaccine
  • Splenectomy
  • Inability to form antibodies (e.g. multiple meyloma or HIV)
  • Rare immune deficiencies
  • Prior respiratory infection
  • COPD, asthma, smoking
  • Conditions that cause poorly functioning PMNs (alcoholism, diabeted, renal insuffiency)
40
Q

What are the most common clinical presentations of Strep pneumoniae?

A 
Otitis
Sinusitis
Bronchitis
Pneumonia
Meningitis
Bacteremia
41
Q

What are most common bacterial causes of otitis?

A

Strep pnemo and H. influenza

42
Q

What are most common bacterial causes of meningitis?

A

Strep pneumo and Neisseria gonorrhea
(can differentiate since Neisseria will cause rash and Strep pneumo will also likely present in a second manner in addition to the meningitis)

43
Q

What is the treatment for Strep pneumo meningitis?

A

Ceftriaxone and vancomycin

need vancomycin in case of penicillin resistance, usually start treatment immediately before culture results return

44
Q

What is the treatment for Strep pneumo pneumonia?

A

Ceftriaxone and macrolide

45
Q

What population is the Pneumovax vaccine for?

A

Adults over 65

46
Q

What population is the Prevnar vaccine for?

A

All children

47
Q

What biochemical test results indicate Enterococcus?

A

Catalase neg, PYR pos, LAP pos

48
Q

What is the most important virulence property of Enterococcus?

A

Resistant to many antibiotics (during antibiotic treatment, other bugs get wiped out and enterococci are favored)

49
Q

What is the treatment for E. faecalis?

A

Ampicillin (or vancomycin if penicillin resistant)

50
Q

What is the treatment for E. faecalis endocarditis?

A

Ampicillin + an aminoglycoside

51
Q

What is the treatment for E. faecium?

A

Vancomycin

52
Q

What is the treatment for E. faecium endocarditis?

A

Vancomycin + an aminoglycoside

53
Q

What is the treatment for E. faecium if it is VRE?

A

Linezolid or daptomycin

54
Q

What are the common clinical presentations of Enterococci?

A

Bacteremia
Endocarditis
UTI
Intra-abdominal and pelvic infection

55
Q

How would you differentiate Enterococcus central-line bacteremia and Enterococcus endocarditis?

A

Echocardiogram to test for endocarditis

56
Q

What are peripheral signs of endocarditis?

A

Osler node - painful, finger tips

Janeway lesion - not painful

57
Q

What population commonly is at risk for Enterococcal UTI?

A

Males with benign prostatic hypertrophy

58
Q

If enterococcus comes back from wound culture, should you treat it?

A

No, unless from a deep or sterile culture

Bacteriology (19 decks)

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