Streptococci + Enterococci

Question 1

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

Answer 1

Streptococcus pyogenes = Group A

Streptococcus agalactiae = Group B

Question 2

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

Answer 2

Staph is catalase positive, strep is catalase negative

Question 3

Contrast how strep and staph appear in culture.

Answer 3

• Staph are cocci that grow in clusters

- Strep are cocci that grow in pairs and chains

Question 4

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

Answer 4

• Alpha: incomplete hemolysis
• Beta: complete hemolysis
• Gamma: No hemolysis

Question 5

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

Answer 5

Both beta

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

What are the sx of acute pharyngitis?

What demo gets it?

Answer 8

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

(5% asymptomatic carriers. Transmitted by respiratory droplets)

Question 9

How does acute pharyngitis resolve?

Why does it reoccur? (be specific)

Answer 9

• Resolves on its own (self-limiting)

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

Question 10

What is impetigo (describe dz)?

What demo gets it?

Answer 10

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

Question 11

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

What body area is most affected?

Answer 11

• 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

Question 12

What causes Scarlet fever (be specific)?

Describe the signs/sx.

Answer 12

• 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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

• Staph. aureus

- Group A strep

Question 15

What demo typically suffers from puerperal sepsis?

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

Answer 15

• 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

Question 16

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

Answer 16

1. Rheumatic fever

2. Acute glomerulonephritis

Question 17

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?

Answer 17

• 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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

• 1. Streptococcal pyrogenic exotoxins (SPE)
• 2. M protein
• 3. Streptolysins
• 4. Streptokinase
     
     5. Capsular polysaccharide
     6. Lipoteichoic acid
     7. Hemolysins
     8. Hyaluronidase
     9. Nucleases
     10. C5a peptidase

Question 20

What do SPEs work as strep A virulence factors?

Answer 20

Streptococcal pyrogenic exotoxins

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

Question 21

Differentiate b/w exo and endotoxin.

Answer 21

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

Question 22

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

Answer 22

• 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)

Question 23

How does streptolysin serve as a strep A virulence factor?

What are the 2 types?

Answer 23

As a hemolysin

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

Question 24

What are the 3 drugs of choice for streptococcus pyogenes?

Answer 24

PCN, ampicillin, amoxicillin

- Cyclosporins could also work

Question 25

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

Answer 25

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

Question 26

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

Answer 26

Erythromycin

Question 27

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

Answer 27

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

Question 28

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

Answer 28

Streptococcus agalactiae (GBS = group B strep)

Question 29

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

Answer 29

Vaginal/rectal swabs collected at 35-37 weeks gestation

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

What is the drug of choice to fight S. agalactiae? | What could you add to enhance killing?

Answer 32

Penicillin or ampicillin | - Gentamycin

Question 33

Describe the limitations for Rapid Group A Detection kits. | What happens if someone is negative on rapid strep?

Answer 33

Not that sensitive: best sensitivity only close to 85% | - Everyone who is negative therefore gets cultured

Question 34

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

Answer 34

Bovis group

Question 35

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

Answer 35

Carcinoma of colon

Question 36

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

Answer 36

- S. anginosus - S. constellatus - S. intermedius

Question 37

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

Answer 37

- Abiotrophia | - Granulicatella

Question 38

``` 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 ```

Answer 38

Rheumatic fever

Question 39

Is strep pneumoniae gram-pos or negative?

Answer 39

Gram-positive | Most common cause of community acquired acute bacterial pneumonia

Question 40

Describe the shape of s. pneumoniae on culture?

Answer 40

- 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.

Question 41

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

Answer 41

Alpha (incomplete)

Question 42

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

Answer 42

- Catalase negative - Bile soluble - Inhibited by ethylhydrocupreine (Optochin)

Question 43

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

Answer 43

- Penicillin if susceptible - Cefotaxime or ceftriaxone if susceptible - Alternative agents: Macrolides: Erythromycin, Clarithromycin, Azithromycin. Fluoroquinolones: Levofloxacin, Moxifloxacin

Question 44

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

Answer 44

1. E. faecalis susceptible to pen / amp | 2. E. faecium resistant to pen / amp

Question 45

List the 3 most common infections caused by Enterococcus species. (Do you heart trees?)

Answer 45

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

Question 46

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

Answer 46

S. Pneumoniae

Question 47

Enterococcus are formally known as group ___ streptococci.

Answer 47

D

Question 48

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

Answer 48

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

Question 49

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

Answer 49

PYR (they are PYR positive)