Streptococci and Enterococci

Question 1

Are Streptococci catalase positive or negative?

Answer 1

Negative

Question 2

What do Streptococci look like microscopically?

Answer 2

Gram positive cocci in pairs and chains

Question 3

What are the different classifications of Strep based on hemolysis?

Answer 3

Beta-hemolytic = complete hemolysis
Alpha-hemolytic = partial
Gamma-hemolytic = non-hemolytic

Question 4

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

Answer 4

Strep pyogenes

Question 5

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

Answer 5

Strep agalactiae

Question 6

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

Answer 6

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

Question 7

What is M protein?

Answer 7

• 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)

Question 8

What toxins are secreted by Group A Strep?

Answer 8

Hemolysins

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

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

Question 9

What causes scarlet fever?

Answer 9

Spe A and Spe C (streptococcal pyrogenic exotoxins)

Question 10

What causes Strep toxic shock syndrome?

Answer 10

Spe A and Spe C (streptococcal pyrogenic exotoxins)

Question 11

What is the function of streptokinase?

Answer 11

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

Question 12

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

Answer 12

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

Question 13

What are signs of bacterial pharyngitis?

Answer 13

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

Question 14

Do rapid antigen tests have better specificity or sensitivity?

Answer 14

Better specificity.

Not as good sensitivity (false negatives)

Question 15

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

Answer 15

Penicillin

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

Question 16

What are symptoms of scarlet fever?

Answer 16

Rash on trunk
Strawberry tongue
Desquamation of skin

Question 17

What is the treatment for impetigo?

Answer 17

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

Question 18

What organisms can cause impetigo?

Answer 18

Group A Strep and Staph aureus

Question 19

What is erysipelas?

Answer 19

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

Question 20

What organisms can cause erysipelas?

Answer 20

High characteristic of beta-hemolytic Strep

Question 21

What disorder do these clinical clues suggest:

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

Answer 21

Necrotizing fasciitis

Question 22

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

Answer 22

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

Question 23

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

Answer 23

Deposition of immune complexes

Question 24

What are the clinical criteria necessary to diagnose rheumatic fever?

Answer 24

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

Question 25

What population is at highest risk for Group B Strep?

Answer 25

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

Question 26

What is treatment for Group B Strep?

Answer 26

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

Question 27

What larger taxonomic group does Strep anginosis fall in?

Answer 27

Strep milleri

Question 28

What are common clinical manifestations of Strep anginosis infection?

Answer 28

Cause abscesses (liver, brain, peridontal)

Question 29

Is Strep anginosis alpha, beta, or gamma hemolytic?

Answer 29

Trick question! Can be all three

Question 30

Are Viridans Strep alpha, beta, or gamma hemolytic?

Answer 30

Alpha and gamma

Question 31

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

Answer 31

Colonoscopy | S. bovis is associated with colonic neoplasia

Question 32

What are common clinical manifestations of Viridans strep?

Answer 32

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

Question 33

What is treatment for Viridans strep?

Answer 33

Penicillin or vancomycin (if resistant to penicillin)

Question 34

What are the two major Enterococcus species?

Answer 34

E. faecalis, E. faecium

Question 35

Is Strep pneumoniae alpha, beta, or gamma hemolytic?

Answer 35

Alpha hemolytic

Question 36

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

Answer 36

Optochin disk on blood agar plate - Strep pneumo is susceptible

Question 37

What are the virulence factors of Strep pneumoniae?

Answer 37

- Evades host immunity (capsule, pneumolysin) - Adheres to host surfaces (phosphocholine, surface adhesion proteins) - Produces very few toxins

Question 38

What may often precede a Strep pneumoniae infection?

Answer 38

Viral infection

Question 39

What are risk factors for Strep pneumoniae infection?

Answer 39

- 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)

Question 40

What are the most common clinical presentations of Strep pneumoniae?

Answer 40

``` Otitis Sinusitis Bronchitis Pneumonia Meningitis Bacteremia ```

Question 41

What are most common bacterial causes of otitis?

Answer 41

Strep pnemo and H. influenza

Question 42

What are most common bacterial causes of meningitis?

Answer 42

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)

Question 43

What is the treatment for Strep pneumo meningitis?

Answer 43

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

Question 44

What is the treatment for Strep pneumo pneumonia?

Answer 44

Ceftriaxone and macrolide

Question 45

What population is the Pneumovax vaccine for?

Answer 45

Adults over 65

Question 46

What population is the Prevnar vaccine for?

Answer 46

All children

Question 47

What biochemical test results indicate Enterococcus?

Answer 47

Catalase neg, PYR pos, LAP pos

Question 48

What is the most important virulence property of Enterococcus?

Answer 48

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

Question 49

What is the treatment for E. faecalis?

Answer 49

Ampicillin (or vancomycin if penicillin resistant)

Question 50

What is the treatment for E. faecalis endocarditis?

Answer 50

Ampicillin + an aminoglycoside

Question 51

What is the treatment for E. faecium?

Answer 51

Vancomycin

Question 52

What is the treatment for E. faecium endocarditis?

Answer 52

Vancomycin + an aminoglycoside

Question 53

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

Answer 53

Linezolid or daptomycin

Question 54

What are the common clinical presentations of Enterococci?

Answer 54

Bacteremia Endocarditis UTI Intra-abdominal and pelvic infection

Question 55

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

Answer 55

Echocardiogram to test for endocarditis

Question 56

What are peripheral signs of endocarditis?

Answer 56

Osler node - painful, finger tips | Janeway lesion - not painful

Question 57

What population commonly is at risk for Enterococcal UTI?

Answer 57

Males with benign prostatic hypertrophy

Question 58

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

Answer 58

No, unless from a deep or sterile culture