Part 2: Strep

Question 1

How to differentiate between staphylococci and streptococci:

Answer 1

• staph: catalase positive.
• strep: catalase negative.

Question 2

The three types of hemolysis on blood agar:

Answer 2

1. beta: complete destruction; golden-yellow.
2. alpha: partial destruction; brown-green.
3. gamma: no destruction.

Question 3

What are Lancefield Groups?

Answer 3

• Serological classification based on antigenic cell wall polysaccharide C-substance on streptococci.

Question 4

Virulence factors of Group A Strep (strep pyogenes) (4):

Answer 4

1. M-protein (antiphagocytic; mimics cardiac myosin).
2. Streptolysin (lyses RBCs).
3. Pyrogenic superantigen exotoxins.
4. Streptokinase.

Question 5

Clinical manifestations of Group A Strep (S. pyogenes) infection:

Answer 5

1. Pharyngitis/cellulitis/impetigo.
2. Scarlet Fever.
3. Toxic shock-like syndrome.
4. Necrotizing fasciitis.

Question 6

Post-infection diseases/conditions caused by Group A Strep (S. pyogenes) infection:

Answer 6

ANTIBODY MEDIATED.

1. Rheumatic Fever (heart and joints; M protein).
2. Glomerulonephritis (kidney).

Question 7

Treatment for Group A Strep (S. pyogenes) infection:

Answer 7

• Penicillin G.
• If skin infection, oxacillin (may be staph, which is penicllin-resistant).

Question 8

Diagnostic identification of Group A Strep (S. pyogenes) (4):

Answer 8

1. gram-positive cocci in chains.
2. catalase negative.
3. beta-hemolytic.
4. bacitracin sensitive.

Question 9

How can you differentiate Group A Strep (pyogenes) from Group B Strep (agalactiae)?

Answer 9

• GAS: bacitracin sensitive (ring around disk on agar).
• GBS: bacitracin resistant (no ring around disk on agar).

Question 10

Diagnostic identification of Group B Strep (S. agalactiae) (4):

Answer 10

1. gram-positive cocci in chains.
2. catalase negative.
3. beta-hemolytic.
4. bacitracin resistant.

Question 11

Clinical manifestations of Group B Strep (S. agalactiae):

Answer 11

1. neonatal meningitis.
2. neonatal sepsis.
3. neonatal pneumonia.

Question 12

Treatment for Group B Strep (S. agalactiae):

Answer 12

Penicillin G.

Question 13

How are neonates infected with Group B Strep (S. agalactiae)?

Answer 13

at birth in the vaginal canal.

Question 14

The two alpha-hemolytic streptococci:

Answer 14

1. Strep viridans.
2. Strep pneumoniae.

Question 15

Clinical manifestations of Strep Viridans infection:

Answer 15

1. subacute endocarditis
2. dental caries

Question 16

Treatment for Strep Viridans infection:

Answer 16

Penicillin G.

Question 17

Diagnostic identification of Strep Viridans (5):

Answer 17

1. gram-positive cocci in chains.
2. catalase negative.
3. alpha-hemolytic.
4. optochin resistant.
5. bile-salt resistant.

Question 18

Where does Strep Viridans normally reside in humans, and how does it enter to cuase infection?

Answer 18

• oral cavity.
• dental or oral surgical procedures.

Question 19

What predisposes someone to Strep Viridans-caused subacute endocarditis?

Answer 19

• Heart valve damage or prosthetic valves.
• Require prophylactic antibiotics before dental procedures.

Question 20

Clinical manifestations of Strep Pneumoniae:

Answer 20

MOPS

1. Meningitis
2. Otitis Media
3. Pneumonia
4. Sinusitis/Septicemia

Question 21

Shape of Strep Pneumoniae bacterial cells:

Answer 21

lancet-shaped diploccocci.

Question 22

Virulence factors of Strep Pneumoniae (3):

Answer 22

1. polysaccharide capsule.
2. pneumolysin (IgA protease).
3. autolysin.

Question 23

Which groups of patients are susceptible to Strep Pneumoniae infection?

Answer 23

• young, old, immunocomprommised.
• sickle cell or asplenic (spleen removes encapsulated pathogens).

Question 24

Diagnostic identification of Strep pneumoniae (5):

Answer 24

1. gram-positive lancet diplococci.
2. catalase negative.
3. alpha-hemolytic.
4. optochin and bile sensitive.
5. positive quelling reaction (swell with antisera).

Question 25

Treatment for Strep pneumoniae infection:

Answer 25

1. ceftriaxone (cephalosporin). 2. erythromycin (macrolides).

Question 26

The two vaccines for Strep pneumoniae:

Answer 26

* Adults: 23-valent polysaccharide vaccine; IgM response. * Children \<5: conjugated vaccine PCV13; IgG response.

Question 27

The 3 types of Group D Streptococci:

Answer 27

1. S. bovis. 2. E. faecalis. 3. E. faecium.

Question 28

What streptococcus is highly correlated with colon cancer?

Answer 28

* S. bovis (group D). ## Footnote **“bovis in the blood, cancer in the colon”**

Question 29

Clinical manifestations of E. faecalis and E. faecium:

Answer 29

**“Do U heart trees?”** 1. UTIs 2. endocarditis 3. biliary tree infections

Question 30

How can you differentiate between enterococci and non-enteroccoci (S. bovis)?

Answer 30

* Both grow in bile and hydrolyze esculin. * Only enteroccoci grow in 6.5% NaCl (NaCl resistant).

Question 31

Why are enteroccoci significant nosocomial infections?

Answer 31

* Hardy; persist on fomites. * Multidrug resistant.

Question 32

Natural habitat of enterococci:

Answer 32

GI tract.

Question 33

1st line treatment for enterococci:

Answer 33

ampicillin + gentamycin + streptomycin.

Question 34

Treatment for VRE:

Answer 34

linezolid and tigecycline.