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PoD Test 2 > Streptococci > Flashcards

Streptococci Flashcards

1
Q

How is streptococci classified?

A

Hemolysis and serologic specificity

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2
Q

What are the different hemolysis patterns?

A

Beta-hemolytic - complete hemolysis

Alpha - hemolytic - partial hemolysis

Gamma-hemolytic - no hemolysis

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3
Q

What are some general characteristics of streptococci?

A

Gram +

Non-motile

Catalase negative

Complex nutritional requirement

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4
Q

What are some characteristics of Streptococcal pyogenes?

A

Hyaluronate capsule

B-hemolytic

M-proteins (150 types)

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5
Q

What is the virulence factor of M proteins?

A

Inhibits opsonization by interfering binding of C3b and degrades C3b

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6
Q

What is streptolysin O?

A

Toxin produced by S. pyogenes

Lyses leukocytes, platelets, and erythrocytes

Immunogenic, indicating a recent GAS infection

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7
Q

What is streptolysin S?

A

Serum stable

Lyses leukocytes, platelets, and erythrocytes

Stimulates the release of lysosomal enzymes

B-hemolysis

nonimmunogenic

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8
Q

What is an important marker of cutaneous group A streptococcal infections?

A

Anti-DNase B

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9
Q

What is DNase?

A

Depolymerizes cell free DNA in pus; contributes to spread from local site

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10
Q

What is the function of streptokinase?

A

catalyzes activation of plasmin to lyse blood clots

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11
Q

What is pharyngitis?

A

Suppurative streptococcal disease (Strep Throat)

Exudates on tonsils

Children 5-15

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12
Q

What is Scarlet Fever?

A

Complication of Strep pharyngitis that occurs when the infecting strain is lysogenized by a bacteriophage that produces a pyrogenic exotoxin

Red maculopapular rash on trunk that spreads to extremities - intense at skin folds

Rash disappears within 5-7 days

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13
Q

What is Impetigo?

A

Streptococcal pyoderma cutaneous infection

Purulent with crusting

Colonization due to direct contact with an infected person or fomite

Young children, poor hygiene

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14
Q

What is Erysipelas?

A

Strep infection

Localized pain, inflammation, lymph node enlargement

Fiery red, advancing erythema - face or legs

Systemic signs - chills, fever and leukocytosis

All age groups

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15
Q

What is necrotizing fasciitis?

A

Rapidly spreading gangrene of skin and fascia

Streptococcal pyrogenic exotoxin released

Surgical debridement required

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16
Q

What are the two types of Necrotizing Fasciitis?

A

Type 1 - Polymicrobial, often anaerobes, occurs in diabetics, immunocompromised and post-surgery

Type 2 - Group A Strep, occurs in otherwise healthy people after skin injury

17
Q

What is the classic case of Necrotizing Fasciitis?

A

Minor skin trauma with redness/warmth

Pain out of proportion to exam

Fever, hypotension

18
Q

What is acute glomerular nephritis?

A

Acute inflammation of the renal glomeruli with edema, hypertension, hematuria and proteinuria

Can be post-skin or post-pharyngitis, caused by M protein

Nephritic syndrome 2-3 weeks after GAS infection

19
Q

What is Acute Rheumatic Fever?

A

Post-pharyngitis Pancarditis (endo, peri, and myo)

Due to cross-reactivity of anti-M protein antibody with cardiac tissue (Type II autoimmune rxn)

Symptoms: migratory arthritis, subcutaneous nodules, carditis and eythema marginatum

20
Q

What is the treatment for rheumatic fever?

A

Penicillin

21
Q

What is PANDAS?

A

Post-streptococcal Autoimmune, Neuropsychiatric Disorders Associated with Streptococci

Used to describe a subset of children whose symptoms of OCD or tic disorders are exacerbated by GAS infection

22
Q

What are some characteristics of Group B streptococcus?

A

G+

CAMP test positive

Hydrolyzes hippurate

B-hemolytic

Infects infants and colonizes vagina

23
Q

What are some characteristics of Streptococcus pneumoniae?

A

G+

CAMP test negative

A-hemolyic (aerobically)

B-hemolytic (anaerobically)

Catalase negative

24
Q

What are the virulence factors of S. pneumoniae?

A

Capsules

Biofilm formation

IgA proteases

Adhesins

Pneumolysin - destroys ciliated epithelial cell

25
Q

What are four S. pneumoniae infections?

A

Lobar pneumonia

Meningitis

Sinusitis

Otitis media

26
Q

How do you diagnose S. pneumoniae infections?

A

Gram stain

Quellung reaction - Polyvalent anti-capsular antibodies mixed with bacteria; increase refractive mass

Bile sensitive

Optochin sensitive

27
Q

What are the clinically important T-independent antigens for B-cell activation?

A

Polysaccharides forming the thick capsules of pathogenic bacteria

E.g. S. pneumoniae, H. flu b, N. meningitidis

28
Q

Where does T-independent B-cell activation occur?

A

Spleen marginal zone

Region between red and white pulp where marginal zone B cells reside

MZ B cells are more easily activated by antigens

29
Q

What is the treatment for Strep infections?

A

Penicillin

Vancomycin w/ ceftriaxone (in the case of penicillin allergy)

30
Q

What are the vaccines for strep infections?

A

PPSV-23 adult vaccine

PCV-13 - child vaccine as a four dose series

PoD Test 2 (23 decks)

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