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MHD > Streptococci + Enterococci > Flashcards

Streptococci + Enterococci Flashcards

1
Q

Name the species of streptococci associated with Lancefield groups A and B.

A

Streptococcus pyogenes = Group A

Streptococcus agalactiae = Group B

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2
Q

What test is the major differentiator b/w staph and strep?

A

Staph is catalase positive, strep is catalase negative

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3
Q

Contrast how strep and staph appear in culture.

A
  • Staph are cocci that grow in clusters

- Strep are cocci that grow in pairs and chains

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4
Q

Differentiate amongst the alpha, beta, and gamma hemolytic classes.

A
  • Alpha: incomplete hemolysis
  • Beta: complete hemolysis
  • Gamma: No hemolysis
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5
Q

Are strep and staph alpha, beta, or gamma-hemolytic?

A

Both beta

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6
Q

*List 6 (there are actually 7) clinical manifestations of Streptococcus pyogenes infection. (there will be more questions detailing them, but these AREN’T objectives)

A
  1. Acute pharyngitis
  2. Impetigo
  3. Erysipelas
  4. Scarlet fever
  5. Necrotizing fasciitis
  6. Toxic-shock-LIKE syndrome
  7. Puerperal Sepsis
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7
Q

Besides group A & B strep, provide 4 other groups we should know. (not an objective but good overview)

A
  1. Other Beta hemolytic streptococci
  2. Viridans group streptococci
  3. Nutritionally Deficient streptococci
  4. Streptococcus pneumoniae
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8
Q

What are the sx of acute pharyngitis?

What demo gets it?

A
  • Fever, sore throat, headache, swollen lymph nodes
  • 5-15 year old

(5% asymptomatic carriers. Transmitted by respiratory droplets)

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9
Q

How does acute pharyngitis resolve?

Why does it reoccur? (be specific)

A
  • Resolves on its own (self-limiting)

- Recurs because there are 80 forms of M protein (AB only adds one at a time)

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10
Q

What is impetigo (describe dz)?

What demo gets it?

A
  • Localized skin disease: pustule with yellow crust; appears on face or extremities (a/w trauma, insect bites)
  • 2-5 y/o children
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11
Q

What is erysipelas/what sx are associated w/it?

What body area is most affected?

A
  • Spreading erythema with well demarcated edge on the face
  • Fever and lymphadenopathy
  • Lesions often on face and often with accompanying steptococcal pharyngitis
  • Legs most often affected
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12
Q

What causes Scarlet fever (be specific)?

Describe the signs/sx.

A
  • Caused by erythrogenic exotoxin (complication of streptococcal pharyngitis)
  • Fever, followed by rash (12-48 hrs later) first appears as tiny red bumps on the chest and abdomen: fine, red, and rough-textured blanches upon pressure. Generally starts on the chest, armpits, and behind the ears
  • Spares the face (although some circumoral pallor is characteristic)
  • Rash fades (desquamation) 3-4 days after appearance
  • Bright red tongue with a “strawberry” appearance
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13
Q

What tissue layer does necrotizing fasciitis affect?
How dangerous is it?
What’s an important sign to recognize it?

A
  • Deep subQ tissue
  • Mortality exceeds 50%
  • Pain exceeds appearance of what it should be
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14
Q

Toxic shock toxin syndrome 1 is often caused by the bacteria ___________, while toxic shock-like syndrome is often caused by the bacteria ___________.

A
  • Staph. aureus

- Group A strep

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15
Q

What demo typically suffers from puerperal sepsis?

What kind of conditions can it lead to? (don’t memorize)

A
  • Seen in women following delivery or abortion
  • Organisms colonizing genital tract or from obstetrical personnel invade the upper genital tract causing endometritis, lymphangitis, bacteremia, necrotizing fasciitis, and streptococcal toxic shock syndrome
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16
Q

Name two diseases that occur as sequelae to streptococcal A infections.

A
  1. Rheumatic fever

2. Acute glomerulonephritis

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17
Q

What type of dz is rheumatic fever?
When does it occur w/r/t strep pharyngitis?
Associated sx?
How is it related to the heart?

A
  • Nonsuppurative inflammatory disease
  • Occurs 1-5 weeks after strep pharyngitis
  • Fever, carditis, subcutaneous nodules, chorea, polyarthritis (Attacks reoccur into adulthood)
  • Characteristic cardiac lesions = Aschoff bodies and valvular damage leads to possible endocarditis later in life
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18
Q

Why does acute glomerulonephritis sometimes occur s/p strep A infections?
Associated sx?

A
  • Certain M types are “nephritogenic”- Ag + AB + C’ deposited in glomeruli
  • Edema, HTN, hematuria, proteinuria
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19
Q

Name 4 virulence factors associated with Streptococcus pyogenes (and try to think of up to 10).

A
    1. Streptococcal pyrogenic exotoxins (SPE)
    1. M protein
    1. Streptolysins
    1. Streptokinase
      1. Capsular polysaccharide
      2. Lipoteichoic acid
      3. Hemolysins
      4. Hyaluronidase
      5. Nucleases
      6. C5a peptidase
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20
Q

What do SPEs work as strep A virulence factors?

A

Streptococcal pyrogenic exotoxins

  • Superantigens that stimulate cytokine response leading to shock and organ failure
  • A, B, and C types
21
Q

Differentiate b/w exo and endotoxin.

A

Endotoxin: released from gram-pos
Exotoxin: part of LPS (lipid A) of gram-neg

22
Q

How does M protein work as a strep A virulence factor?

A
  • Binds to epidermal cells, allows bacteria to survive (strains without M protein are avirulent)
  • Antiphagocytic (degrades complement C3b) (ABs to M protein activate complement and kill the bacteria)
23
Q

How does streptolysin serve as a strep A virulence factor?

What are the 2 types?

A

As a hemolysin

  • Streptolysin S (oxygen stable, non-antigenic)
  • Streptolysin O (oxygen labile, ASO antibodies)
24
Q

What are the 3 drugs of choice for streptococcus pyogenes?

A

PCN, ampicillin, amoxicillin

- Cyclosporins could also work

25
Q

What are 3 antimicrobials we’ve learned so far that have no resistance worldwide?

A

PCN, ampicillin, amoxicillin (they do have allergies, though)

26
Q

If a pt is allergic to PCN, what might you given them to treat S. pyogenes?

A

Erythromycin

27
Q

What infections are a/w Streptococcus agalactiae? (no objective)

A
  • *Neonatal pneumonia, sepsis, meningitis
  • Skin and wound infections in adult diabetic patients
  • Endocarditis
    (Part of normal flora in throat, vaginal and GI tract)
28
Q

What bacteria is a/w perinatal GBS (group B strep) disease?

A

Streptococcus agalactiae (GBS = group B strep)

29
Q

When should cultures be performed for perinatal GBS dz, and what should be swabbed?

A

Vaginal/rectal swabs collected at 35-37 weeks gestation

30
Q

What are the 3 types of perinatal GBS disease, and the sx a/w each?

A
  1. Early-onset neonatal disease (1st week of life): bacteremia, PNA, or meningitis
  2. Late-onset neonatal disease (1 week to 3 months age): bacteremia w/ meningitis
  3. Pregnant women: UTI’s and carrier
31
Q

Explain the role of S. agalactiae (Strep B) in causing neonatal disease. (pathogenesis)

A
  1. Maternal colonization of vagina or rectum exposes baby at delivery
  2. Lack of protective maternal antibody
  3. Sialic acid on polysaccharide capsule inhibits C’ allowing organisms to multiply
32
Q

What is the drug of choice to fight S. agalactiae?

What could you add to enhance killing?

A

Penicillin or ampicillin

- Gentamycin

33
Q

Describe the limitations for Rapid Group A Detection kits.

What happens if someone is negative on rapid strep?

A

Not that sensitive: best sensitivity only close to 85%

- Everyone who is negative therefore gets cultured

34
Q

What’s a group of Viridians streptococci that we should know?

A

Bovis group

35
Q

Isolation of Strep Bovis (Viridians) Group from blood is strongly associated w/ __________.

A

Carcinoma of colon

36
Q

Name the species included in the Strep Milleri Group. (3)

A
  • S. anginosus
  • S. constellatus
  • S. intermedius
37
Q

Name the species included in the Nutritionally-deficient Streptococci Group. (3)

A
  • Abiotrophia

- Granulicatella

38
Q 
A 7-year-old child presents with a fever, pain in his ankles, knees and wrist, and a new heart murmur.  His mother said that he complained of a “sore throat” last month, but the symptoms resolved without taking him to the pediatrician. A rapid screening test for strep throat is negative. His most likely diagnosis is:
Toxic shock-like syndrome
Rheumatic fever
Scarlet fever
Puerperal fever
Acute glomerulonephritis
A

Rheumatic fever

39
Q

Is strep pneumoniae gram-pos or negative?

A

Gram-positive

Most common cause of community acquired acute bacterial pneumonia

40
Q

Describe the shape of s. pneumoniae on culture?

A
  • Gram-positive, lancet-shaped cocci (elongated cocci with a slightly pointed outer curvature).
  • Usually seen as pairs of cocci (diplococci), but they may also occur singly and in short chains.
41
Q

When cultured on blood agar, s. pneumoniae are ______ (alpha/beta/gamma) hemolytic.

A

Alpha (incomplete)

42
Q

Is s. pneumonia catalase pos or neg?
Is it bile soluble or insoluble?
*What is it inhibited by? (special lab test)

A
  • Catalase negative
  • Bile soluble
  • Inhibited by ethylhydrocupreine (Optochin)
43
Q

What are the recommended tx’s for s. pneumoniae? (no treatments are on objectives, part of pharm)

A
  • Penicillin if susceptible
  • Cefotaxime or ceftriaxone if susceptible
  • Alternative agents: Macrolides: Erythromycin, Clarithromycin, Azithromycin. Fluoroquinolones: Levofloxacin, Moxifloxacin
44
Q

List the two major species of Enterococus causing infection in humans.

A
  1. E. faecalis susceptible to pen / amp

2. E. faecium resistant to pen / amp

45
Q

List the 3 most common infections caused by Enterococcus species.

(Do you heart trees?)

A
  1. Urinary tract
  2. Mixed bacterial wound infections and decubiti
  3. Sepsis, endocarditis
46
Q

When cultured on blood agar, this alpha-hemolytic pathogen shows up as “dime-shaped” colonies w/sinking centers.

A

S. Pneumoniae

47
Q

Enterococcus are formally known as group ___ streptococci.

A

D

48
Q

Explain the penicillin (or ampicillin) susceptibility and resistance for E. faecalis and E. faecium.
*What other abx are some strains resistant to?

A
  • E. faecalis susceptible to pen / amp
  • E. faecium resistant to pen / amp
  • Vancomycin (VRE)- Vancomycin-resistant enterococcus, becoming more common
49
Q

What’s an important test that we should know for detecting enterococcus? (are they pos or neg?)

A

PYR (they are PYR positive)

MHD (20 decks)

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