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Dermatology > Streptococci > Flashcards

Streptococci Flashcards

1
Q

Most frequent cause of pharyngitis

A

GAS - strep pyogenes

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2
Q

GAS pharyngitis diagnosis

A

rapid antigen test - High specificity, low sensitivity

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3
Q

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

A

Streptolysin O

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4
Q

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

A

Streptolysin S

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5
Q

alpha hemolysis - green

A

Viridans group Strep

S. pneumoniae

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6
Q

beta hemolysis

A

GAS
GBS
GCS/GGS

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7
Q

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

A

M protein (GAS)

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8
Q

Polysaccharide capsule made of? GAS

A

Hyaluronic acid - antiphagocytic

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9
Q

facilitates spread of GAS in cellulitis/other skin infections

A

Hyaluronidase

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10
Q

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

A

Streptokinase -GAS

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11
Q

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

A

DNase (streptodornase) -GAS

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12
Q

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

A

C5a peptidase

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13
Q

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

A

Streptococcal chemokine protease

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14
Q

Untreated GAS pharyngitis complications

A 
Otitis media
Sinusitis
Mastoiditis
Meningitis
Peritonsillar/retropharyngeal abscess
Rheumatic fever - Immune mediated
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15
Q

GAS Tx

A

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

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16
Q

GAS Tx in Pen allergy pt

A

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

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17
Q

cellulitis, impetigo, erysipelas

A

GAS soft tissue infections

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18
Q

responsible for rash of scarlet fever. Acts as superantigen

A

Erythrogenic toxin - GAS

19
Q

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

A

Pyrogenic exotoxin A - GAS

20
Q

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

A

Exotoxin B - GAS

21
Q

Diagnosis of TSS from GAS

A

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

22
Q

Tx Strep TSS

A

Penicillin plus Clindamycin

23
Q

More frequent after skin infections than pharyngitis

Ag-ab complexes on glomerular basement membrane

A

Post-strep glomerulonephritis

24
Q

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

A

Post-strep glomerulonephritis

25
Q

2 weeks after GAS pharyngitis

A

Acute Rheumatic Fever

26
Q

Jones criteria

A

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

27
Q

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

A

Peptostreptococcus - Tx with penicillin

28
Q

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

A

Indicative of Infective Endocarditis

29
Q

exudative, edematous hemorrhagic lesions of the retina

A

roth spots

30
Q

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

A

100%

31
Q

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

A

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

32
Q

VRE: more likely

A

Enterococcus faecium.

Linezolid or Daptomycin used for treatment in these infections

33
Q

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

A

Strep Bovis

34
Q

Can grow in hypertonic saline or in bile.

A

Enterococcus faecalis/faecium

35
Q

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

A

Enterococcus faecalis/faecium

36
Q

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

A

Streptococcus agalactiae (GBS)

37
Q 
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
A

Streptococcus agalactiae (GBS)

38
Q

Causes neonatal sepsis, meningitis, PNA

Main risk factor: PROM in women colonized; also babies born prior to 37 weeks; children whose mothers lack antibodies

A

Streptococcus agalactiae (GBS)

39
Q

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

A

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

40
Q

Streptococcus agalactiae (GBS) Tx

A

Penicillin/ampicillin (Vanc if allergic)

41
Q

Most common cause of subacute bacterial endocarditis

A

Strep viridans group

42
Q

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

A 
Resistant to lysis by bile
Optochin resistant (strep pneumo is opto sensitive)
43
Q

Cause of dental caries. Synthesizes polysaccharides in dental plaque

A

Strep mutans

Dermatology (8 decks)

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