Streptococci

Question 1

Most frequent cause of pharyngitis

Answer 1

GAS - strep pyogenes

Question 2

GAS pharyngitis diagnosis

Answer 2

rapid antigen test - High specificity, low sensitivity

Question 3

oxygen labile. Causes beta-hemolysis only when colonies grow under surface of blood agar plate

Answer 3

Streptolysin O

Question 4

oxygen stable. Causes beta-hemolysis on surface of plate.

Answer 4

Streptolysin S

Question 5

alpha hemolysis - green

Answer 5

Viridans group Strep

S. pneumoniae

Question 6

beta hemolysis

Answer 6

GAS
GBS
GCS/GGS

Question 7

Protudes from outer surface of cell and interferes with ingestion by phagocytes, 80 serotypes

Answer 7

M protein (GAS)

Question 8

Polysaccharide capsule made of? GAS

Answer 8

Hyaluronic acid - antiphagocytic

Question 9

facilitates spread of GAS in cellulitis/other skin infections

Answer 9

Hyaluronidase

Question 10

activates plasminogen to form plasmin dissolves fibrin in clots, thrombi and emboli

Answer 10

Streptokinase -GAS

Question 11

degrades DNA in exudates/necrotic tissue. Protect the bacteria from being trapped inneutrophil extracellular traps (NETs).

Answer 11

DNase (streptodornase) -GAS

Question 12

cleaves C5a produces by the complement system. Minimizes influx of neutrophils early in infection.

Answer 12

C5a peptidase

Question 13

prevents migration of neutrophils into site of infection by degrading chemokine IL-8 which would recruit neutrophils to site

Answer 13

Streptococcal chemokine protease

Question 14

Untreated GAS pharyngitis complications

Answer 14

Otitis media
Sinusitis
Mastoiditis
Meningitis
Peritonsillar/retropharyngeal abscess
Rheumatic fever - Immune mediated

Question 15

GAS Tx

Answer 15

Oral Penicillin V 500 mg 2-3 times daily x 10 days
Amoxicillin 500 mg BID x 10 days
Cephalexin 500 mg BID x 10 days

Question 16

GAS Tx in Pen allergy pt

Answer 16

Azithromycin 500 mg x 1 followed by 250 mg daily on days 2-5
Clarithromycin 250 mg BID x 10 days
Clindamycin 600 mg TID x 10 days

Question 17

cellulitis, impetigo, erysipelas

Answer 17

GAS soft tissue infections

Question 18

responsible for rash of scarlet fever. Acts as superantigen

Answer 18

Erythrogenic toxin - GAS

Question 19

causes most cases of TSS. Superantigen – causes release of large amounts of cytokines

Answer 19

Pyrogenic exotoxin A - GAS

Question 20

protease that rapidly destroys tissue and is produced in large amounts by the “flesh-eating” strains of GAS that cause necrotizing fasciitis

Answer 20

Exotoxin B - GAS

Question 21

Diagnosis of TSS from GAS

Answer 21

includes isolation of GAS from normally sterile site (blood, CSF, tissue biopsy) and hypotension plus other organ involvement

Question 22

Tx Strep TSS

Answer 22

Penicillin plus Clindamycin

Question 23

More frequent after skin infections than pharyngitis

Ag-ab complexes on glomerular basement membrane

Answer 23

Post-strep glomerulonephritis

Question 24

HTN, facial edema, LE edema, dark urine due to RBCs
Many cases are subclinical
It is unclear if early treatment of the infection can prevent this complication

Answer 24

Post-strep glomerulonephritis

Question 25

2 weeks after GAS pharyngitis

Answer 25

Acute Rheumatic Fever

Question 26

Jones criteria

Answer 26

Joints: polyarthritis (affects several joints in quick succession) Carditis (pancarditis, aortic/mitral valves also affected) Nodules (subcutaneous) (firm painless lesions up to 2 cm in size) Erythema marginatum (evanescent, pink rash involving trunk most often Sydenham chorea (neurologic disorder consisting of abrupt involuntary movements) ASO titer to aid dx

Question 27

Anaerobe, Members of normal flora of gut, mouth, female genital tract

Answer 27

Peptostreptococcus - Tx with penicillin

Question 28

Janeway lesions, Osler's nodes (subacute, painful, violaceous), and Roth spots

Answer 28

Indicative of Infective Endocarditis

Question 29

exudative, edematous hemorrhagic lesions of the retina

Answer 29

roth spots

Question 30

Endocarditis _____ fatal if not treated. 3 sets of blood cultures needed esp in subacute cases to get a positive

Answer 30

100%

Question 31

Hydrolyze esculin in presence of bile (produce black pigment on bile-esculin agar)

Answer 31

Group D Strep - Enterococcus faecalis/faecium, Strep Bovis, e.g.

Question 32

VRE: more likely

Answer 32

Enterococcus faecium. | Linezolid or Daptomycin used for treatment in these infections

Question 33

Causes endocarditis in patients with colon cancer. Very strong association. Will not grow in hypertonic saline Treatment: PCN, Ceftriaxone, or Vancomycin

Answer 33

Strep Bovis

Question 34

Can grow in hypertonic saline or in bile.

Answer 34

Enterococcus faecalis/faecium

Question 35

Cause hospital-acquired UTIs, blood stream infections (many times line-related) and endocarditis

Answer 35

Enterococcus faecalis/faecium

Question 36

Narrow zone of beta hemolysis Lack of hydrolysis of bile esculin agar Hydrolyzes hippurate

Answer 36

Streptococcus agalactiae (GBS)

Question 37

``` Bacitracin resistant (GAS is bacitracin sensitive) CAMP test: protein is produced that enhances hemolysis on sheep blood agar when combined with beta-hemolysin of S. aureus ```

Answer 37

Streptococcus agalactiae (GBS)

Question 38

Causes neonatal sepsis, meningitis, PNA | Main risk factor: PROM in women colonized; also babies born prior to 37 weeks; children whose mothers lack antibodies

Answer 38

Streptococcus agalactiae (GBS)

Question 39

important cause of invasive infections such as septic arthritis, cellulitis, osteomyelitis

Answer 39

Strep agalactiae (GBS) Diabetes main predisposing factor, also breast cancer

Question 40

Streptococcus agalactiae (GBS) Tx

Answer 40

Penicillin/ampicillin (Vanc if allergic)

Question 41

Most common cause of subacute bacterial endocarditis

Answer 41

Strep viridans group

Question 42

How can viridans group strep be distinguished from S. pneumoniae?

Answer 42

``` Resistant to lysis by bile Optochin resistant (strep pneumo is opto sensitive) ```

Question 43

Cause of dental caries. Synthesizes polysaccharides in dental plaque

Answer 43

Strep mutans