Skinny bacteria II Flashcards by tcarlso 3

What is the result for alpha, beta, and gamma hemolysis?

alpha = partial/green
beta = total
gamma = none

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What are the lancefield antigens?

Cell wall carbs used to define beta-hemolytic into groups A through U

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What is GAS?

S. Pyogenes

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What is GBS?

S. agalactiae

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What is GDS?

Enterococcus

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What are the two groups of strep that do not get lancefield designations?

S. pneumoniae

S. mutans

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What are the four major diseases GAS is responsible for?

Strep throat
Skin infections
Rheumatic fever
Glomerulonephritis

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How do you differentiates GAS from other Beta hemolytic strep?

GAS is bacitracin sensitive

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What are the three major virulence factors for GAS?

Hyaluronic acid capsule
Adhesins
Toxins

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What is significant about that capsule of GAS

Hyaluronic acid is a poor immunogen (looks like self) and interferes with phagocytosis

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What are the two toxins of GAS?

Streptolysin

Superantigens

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What is the M protein found on Strep A? (3)

Myosin-like protein that:

prevents phagocytosis
allows for attachment
Inhibits complement attack

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What is the function of streptolysin O and streptolysin S?

Pore forming toxins

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What percent of GAS produce superantigens?

10%

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What are the superantigens that some strep produce? What are their function?

Pyrogenic exotoxins SpeA, SpeB, SpeC

Increase proinflammatory cytokine production

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What is the function of C5a peptidase of GAS?

Prevents complement formation, and PMN chemotaxis

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Strep gets into a cell using what protein? What happens then?

Streptolysin O

Produces more causing apoptosis of the cell

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What are the four major skin infections caused by strep?

Impetigo (pyoderma)
Erysipelas
Cellulitis
Necrotizing fasciitis

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How can you distinguish between staph and strep impetigo?

Staph is more extensive, with bullous lesions

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Sharply demarcated erythematous skin = ?

Erysipelas

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NOT sharply demarcated erythematous and warm skin = ?

Cellultis

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What bacteria is the most common cause of cellulitis?

Strep pyogenes

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GAS causes what % of necrotizing fasciitis?

60%

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What are the symptoms of necrotizing fasciitis? (2)

Extreme pain/TTP

Grayish skin coloration initially, moving to erythema and edema

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What is the treatment for necrotizing fasciitis?

Prompt debridement and removal of tissue Broad spectrum Abx

What causes scarlet fever? Symptoms?

Strep pyogenes exotoxin Spe Strawberry tongue Petechial rash

Strawberry tongue + Petechial rash = ?

Scarlet fever

What are the complications of acute rheumatic fever? What causes it?

Heart valve tissue damage d/t cross rxn w/ M protein and type II hypersensitivity

Glomerulonephritis is a complication of what?

Pharyngeal OR cutaneous GAS

What type of hypersensitivity is glomerulonephritis?

Type III

When does glomerulonephritis present?

1-4 weeks post GAS pharyngitis or 3-6 week post cutaneous infection

Symptoms of glomerulonephritis? (3)

Hematuria, HTN Recent strep infx Reduced serum complement

Strep toxic syndrome usually follow what disease?

Necrotizing fasciitis caused by strep

True or false: Strep toxic syndrome is the result of bacteremia

True

How do you diagnose GAS, besides serology and culture?

**Antistreptolysin O abs**

What is the treatment for GAS? Is staph susceptible to this?

PCN--staph would be resistant to this

What is the gram stain and morphology of pseudomonas aeruginosa? Hemolysis pattern? Oxidase? Ferment?

Gram negative motile rod Beta hemolysis. Oxidase positive Non-fermenter

Is staph sensitive to PCN?

no, has beta lactamases

Where can pseudomonas grow?

Anywhere there is water--even soap

Blue green pigment on agar = ?

Pseudomonas aeruginosa

Pseudomonas aeruginosa usually are associated with what?

Recent hospitalization

True or false: Pseudomonas aeruginosa is an opportunistic pathogen, and has loads of abx resistance

True

What are the soluble pigments that Pseudomonas aeruginosa produces?

Pyocyanin | Pyoverdin

What is the capsule associated with Pseudomonas aeruginosa?

Alginate

What are the adhesins for Pseudomonas aeruginosa? (4)

Pili Flagella LPS Alginate

What is the major exotoxin for Pseudomonas aeruginosa? Function? How is it administered to cells?

Exotoxin A Blocks protein synthesis through inhibition of EF-2 Type III secretion system

What is the MOA of abx resistance for Pseudomonas aeruginosa?

Mutation of pore proteins

CF and burn patients hate what bacteria?

Pseudomonas aeruginosa

What is the common cause of swimmer's ear (otitis externa)?

Pseudomonas aeruginosa

What are the two major soft tissue infections that Pseudomonas aeruginosa causes?

Folliculitis | Osteochondritis

Pseudomonas aeruginosa infections are associated with what type of skin problem?

Burns

Bacteremia caused by Pseudomonas aeruginosa causes what?

Ecthyma gangrenosum

What is Ecthyma gangrenosum?

Necrotic skin lesions and infections of the blood vessels

What predisposes burns to Pseudomonas aeruginosa?

Moist surface + inability of PMNs to penetrate skin

What is Hot tub skin rash? Symptoms?

Pseudomonas folliculitis Pruritic erythematous papules x5 days

What is the cause of "green nails"?

Pseudomonas aeruginosa biofilm/infection of the paronychia

What is webspace intertrigo? Cause?

Macerated and eroded skin on interdigital toes, usually caused by Pseudomonas aeruginosa

What is the treatment for Pseudomonas aeruginosa infections?

Combination therapy with aminoglycosides

What is the function of LTA that strep produces?

Involved in adhering to fibronectin on epithelial cell surfaces

What is the function of proteins F and M on strep?

F = adhesion M = blocks C3b

What is the MOA of the superantigens produced by strep?

Increase proinflammatory cytokines

What is the function of DNAase that strep produces?

Depolymerizes DNA in pus, decreasing viscosity

What is the function of streptokinase produced by strep?

Cleaves plasminogen

Sharply demarcated erythema, with associated fever and chills = ?

Erysipelas

What is the pathogenesis of necrotizing fasciitis?

Dead tissue blocks circulation to the wound creating heaven for bacteria

What is the pathogeneis of rhemuatic fever heart damage?

Strep Pyogenes m M protein looks like heart tissue

Gram positive cocci in clusters = ? (usually)

Staph Aureus

Gram positive cocci in chain = ? (usually)

Strep Pyogenes

What are the symptoms of rheumatic fever? How long after a pharyngeal infx?

Diffuse, erythematous rash on upper chest, then extremities Coating of the tongue (strawberry) 3 week post GAS pharyngitis

How do you distinguish between strep and staph toxic shock syndrome?

``` Staph = intoxication Strep = bacteremia ```

Antibodies against streptolysin O (ASO test) is useful for confirming what disease(s)?

Rheumatic fever or glomerulonephritis

Can cutaneous infections of strep cause acute rheumatic fever?

TSST is produced by what bacteria?

Staph