Bacterial Infections of the Skin Flashcards by tcarlso 3

What are the mild skin infections?

Pyodermal

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What is the scary/severe skin infections?

Necrotizing fascitis

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What are the four minimum diagnostic criteria of bacterial skin infections?

Erythema
Edema
Warmth
and TTP

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What are the bacteria that are associated with DM?

S. Aureus

GBS

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What are the bacteria associated with neutropenia?

Pseudomonas aeruginosa

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What are the bacteria that are associated with hot tubs?

Pseudomonas aeruginosa

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What are the bacteria associated with IV drug abuse?

MRSA

Pseudomonas Aeruginosa

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What is necessary for skin infections to develop?

Breaking of the stratum corenum

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What are the skin infections associated with pores?

Folliculitis, foruncles

acarbuncles

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What is Erysipelas?

Superficial infection of the skin, characterized by well defined, raised borders

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Deep involvement of the subcutaneous skin is called what?

Cellulitis, fasciitis, myositis

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Where is impetigo localized to? In whom?

Around the mouth (honey crusted lesions)

Usually kiddos

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Honey Crusted skin infection = ?

Impetigo

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What is the most common bacterial skin infection in children?

Impetigo

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What is bullous impetigo?

blisters caused by exfoliative toxin of S. Aureus

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What is ecthyma?

Deeper form of impetigo resulting in scarring and ulceration

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Punched out, ulcerative lesions = ?

Ecthyma

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What is the treatment of ecthyma and impetigo?

Gentle debridement and topical abx

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What are boils?

Furuncles (infection of the hair follicle)

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What are Carbuncles? Associated symptoms?

Coalescence of boils (usually caused by S. Aureus lesions on the back of the neck)

Chills and fevers

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What is folliculitis? What usually causes this?

Infection of the hair follicles

Pseudomonas

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What is erysipelas? What organism usually causes this?

Superficial skin infection characterized by sharp borders between infected and unaffected skin

Caused by S. pyogenes

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What is cellulitis?

Deep skin infection without clear borders

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What usually causes cellulitis? Associated symptoms?

Staph aureus, GAS,

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Dog or cat bite cellultiis = ?

Pasteruella multocida

Sea water cellultiis = ?

Vibrio vulnificus

What are paronychia?

Localized infection /abscess of the nailfold

What are is the cause of acute paronychia? Chronic?

``` Acute = S. Aureus Chronic = Candida albicans ```

What is necrotizing fasciitis? What is the usual bacterial cause?

Acute infection of the subcutaneous tissue, including muscle and fat, usually the result of untreated cellulitis. usually caused by Strep. pyogenes

What is the treatment for necrotizing fascisitis?

Surgical debridement

What are the three major organisms of skin infections?

Staph Aureus Strep pyogenes Pseudomonas aeruginosa

Gram stain and morph or Pseudomonas?

Gram negative rod

Where is staph usually found?

SKin and mucous membranes of us

What are the two CoNS?

S. epidemidis | S. Saprphyticus

What is the predominant way of spreading staph?

Nasal shedding

What is the color of staph on agar plates?

Gold (Aureus = gold)

Hemolysis result of staph aureus?

Beta

What is the function of the capsule of staph Aureus?

Biofilm | antiphagocytic

What is the function of peptidoglycan of staph Aureus?

Endotoxin

What is the function of teichoic acid of staph Aureus?

Adhesion

What is the function of protein A of staph Aureus?

Inhibits antibody mediated clearance by binding to IgG Fc domain

What are the cytotoxins produced by staph Aureus? What does each do? (4)

Alpha (pore forming) Exfoliative toxin (mediates SSSS) Enterotoxins (enterotoxin A) TSST-1 superantigen

What does the exofoliative toxin produced by staph Aureus do? What is the syndrome that these cause?

Serine proteases that breaks up desmosomes Staph scalded skin sydrome

What is the function of coagulase that staph Aureus carries?

Breaks up clots

What is the function of hyaluronidase that staph Aureus carries?

Hydolyses hyluronic acid

What is the function of fibrinolysin that staph Aureus carries?

Dissolves fibrin clots

What is the function of lipase that staph Aureus carries?

Hydrolyzes lipids

What is the function of nucleases that staph Aureus carries?

Hydrolyzes DNA

What are the three toxin mediated staph aureus diseases?

1. Scalded skin syndrome 2. food poisoning 3. Toxic shock

Who usually gets scalded skin syndrome for staph?

Babies with staph in their nose

What are the symptoms of staph scalded skin syndrome?

Sunburn like shedding in neonates that slough off with minimal pressure

Why can't staph be cultured from the skin or blood of neonates affected with scalded skin syndrome? What about leukocytes?

Exotoxin Thus leukocytes are also not elevated

How lethal is scalded skin syndrome?

Self limiting if immunocompetent Can be fatal if immunocompromised

What is the MOA of staph aureus exfoliative toxin?

Serine proteases that split desmoglein 1

What is Nikolsky's sign? What does it indicate?

Erythematous, fluid-filled bullae that desquamouses with light touch = SSSS

What is the treatment for SSSS?

supportive + oxacillin/vanco

How do you diagnose SSSS?

Presentation and skin biopsy with cleavage in the upper epidermis

What is the pathology of the boils (furuncles) from staph aureus infection?

infects hair follicle, forms abscess

What is the treatment for Suppurative staph infections? (2)

Lance abscess Abx if wound does not clear or if systemic symptoms

What gives MRSA its resistance to cephalosporins? (2)

Beta lactamase and MecA gene encoding for PBPs

What is the general treatment for staph infections that are not MRSA? (2)

Nafcillin/oxacillin

What is the treatment with MRSA?

vanco

How do you diagnose Staph Aureus infections?

Gram stain | Culture w/ usual stuff

What are the symptoms of osteomyelitis? (4)

Bone pain Fever swelling Malaise

True or false: Osteomyelitis is almost always caused by a bacterial infection?

True

What is the most common cause of osteomyelitis? Second and third?

1. Staph Aureus 2. Strep 3. Pseudomonas

What are the symptoms of septic arthritis?

Painful, erythematous joints with purulent material observed on aspiration

What is the primary cause of septic arthritis of children? Sexually active adults?

Staph aureus Sexy= Neisseria gonorrhoeae

Is there a fever associated with SSSS?

Nope--exotoxin