Bacterial Infections of the Skin Flashcards
What are the mild skin infections?
Pyodermal
What is the scary/severe skin infections?
Necrotizing fascitis
What are the four minimum diagnostic criteria of bacterial skin infections?
Erythema
Edema
Warmth
and TTP
What are the bacteria that are associated with DM?
S. Aureus
GBS
What are the bacteria associated with neutropenia?
Pseudomonas aeruginosa
What are the bacteria that are associated with hot tubs?
Pseudomonas aeruginosa
What are the bacteria associated with IV drug abuse?
MRSA
Pseudomonas Aeruginosa
What is necessary for skin infections to develop?
Breaking of the stratum corenum
What are the skin infections associated with pores?
Folliculitis, foruncles
acarbuncles
What is Erysipelas?
Superficial infection of the skin, characterized by well defined, raised borders
Deep involvement of the subcutaneous skin is called what?
Cellulitis, fasciitis, myositis
Where is impetigo localized to? In whom?
Around the mouth (honey crusted lesions)
Usually kiddos
Honey Crusted skin infection = ?
Impetigo
What is the most common bacterial skin infection in children?
Impetigo
What is bullous impetigo?
blisters caused by exfoliative toxin of S. Aureus
What is ecthyma?
Deeper form of impetigo resulting in scarring and ulceration
Punched out, ulcerative lesions = ?
Ecthyma
What is the treatment of ecthyma and impetigo?
Gentle debridement and topical abx
What are boils?
Furuncles (infection of the hair follicle)
What are Carbuncles? Associated symptoms?
Coalescence of boils (usually caused by S. Aureus lesions on the back of the neck)
Chills and fevers
What is folliculitis? What usually causes this?
Infection of the hair follicles
Pseudomonas
What is erysipelas? What organism usually causes this?
Superficial skin infection characterized by sharp borders between infected and unaffected skin
Caused by S. pyogenes
What is cellulitis?
Deep skin infection without clear borders
What usually causes cellulitis? Associated symptoms?
Staph aureus, GAS,
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?
- Scalded skin syndrome
- food poisoning
- 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?
- Staph Aureus
- Strep
- 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