Skin and Soft Tissue Infections Flashcards
What is the main composition of normal skin flora on epidermis?
staphylococcus epidermidis
What bacteria is commonly associated with acne?
propionibacterium
What is a macule?
a flat lesion that cannot be palpated, like a freckle
How does a vesicle form?
accumulation of fluid under the epidermis
What is a papule?
a raised lesion resulting from accumulation of material in the dermis
What is a pustule?
a pus-filled raised lesion on the skin, results as a buildup of the cellular debris of inflammatory cells under the epidermis
What skin rash is characterized by “large papule that travels deeper into the skin, not visible”
nodule
What is a bullae?
a large fluid filled vesicle, will rupture easily and create a portal of entry, the skin is NOT raised
What skin rash is the start of necrotizing fasciitis?
bullae
Which skin rash is characterized by “often referred to as “hives”, due to allergies, raised, itchy area of the skin”?
Wheal
What is a plaque?
- a large, raised area that forms a plateau
- autoimmune disease, psoriasis
- sharp edges
Which skin rash is typically due to an autoimmune disease such as psoriasis?
plaque
How are plaques typically treated?
topical corticosteroids
What are some sampling techniques for skin and soft tissue infection?
- skin scraping
- biopsy and needle aspiration (pus and tissue)
- swabs useful is sample contains suspected pathogen (deep inside)
What is the most common way skin infections arise?
exogenous penetration (trauma, surgery, bite)
Which bacteria colonizes the nasopharynx, axillae, rectum, skin?
staphylococcus aureus
What infections do staphylococcus aureus cause?
- heart valves, kidneys, brain, bacteremia, food poisoning
Which group of bacteria colonizes the nasopharynx and skin and is beta-hemolytic?
Group A streptococcus
What type of infections does GAS cause?
- strep throat, scarlet fever, rheumatic fever, glomerulonephritis
What infection is characterized by “pain, tenderness, and localized edema, with lesions that vary in size and may scar despite resolution”?
folliculitis
What pathogens cause Folliculitis?
S. aureus, pseudomonas aeruginosa, candida albicans
How long does it take for folliculitis to resolve?
1-2 weeks
What are furuncles (boils), and how do they come about?
large, painful, raised nodular lesion - extension of folliculitis into surrounding hypodermis (from people trying to squeeze)
- grows larger and more painful (5-7 days) before it develops a yellow white tip that then ruptures and drains
What do multiple furuncles turn into?
carbuncle, occurs in areas where skin is much thicker, deep infection of multiple hair follicles, sometimes associated with fever
What skin infection is associated with those under 5 years old, the elderly and the immunocomprimsed?
Staphylococcal scalded skin syndrome
What is staphylococcal scalded skin syndrome?
Toxins cause cells within the outer epidermis to separate from each other and from underlying tissues – systemic effect (toxemia)
Redness and wrinkling of the skin commonly appears first on the mouth, then spreads across entire body, followed by the formation of clear, fluid filled blisters
Exotoxin travels from site of infection through the bloodstream causing wide spread epidermal response to the exotoxin
How do we treat staphylococcal scalded skin syndrome?
IV nafcillin or oxacillin therapy (aggressive)
What pathogen causes staphylococcal scalded skin syndrome?
specific strains of S. aureus produce exfoliative exotoxins
What skin infection is characterized by “redness and wrinkling of the skin that first appears around mouth and spreads through entire body, followed by the formation of clear, fluid filled blisters”?
Staphylococcal scalded skin syndrome
Which skin infection is common in children 2-5 years old and spikes in the summer months?
impetigo/ pyoderma
What infection is characterized by “small, flattened, red patches on face and limbs that become vesicles and then pustules that rupture and crust over (gold) and are very itchy until healed”?
impetigo/ pyoderma
What are the causative pathogens of Impetigo/ Pyoderma?
S. aureus and S. pyogenes
Which skin infection if not promptly treated can lead to necrotizing fasciitis?
Impetigo/ pyoderma
How do we treat Impetigo if there are limited lesions vs multiple severe lesions?
limited lesions: topical mupirocin
multiple: PO clindamycin or doxycycline
Which skin infection is characterized by “demarcated area of painful erythema and induration (raised margin), “butterfly wing” lesion”?
Erysipelas
What population does Erysipelas commonly affect?
requires portal of entry, children and elderly (face, arms, legs)
Which skin infection is “an acute infection of the dermis and dermal lymphatics”?
Erysipelas
What are some signs and symptoms of Erysipelas?
- swollen lymph nodes
- pain, fever, chills
- increased WBCs
- risk of bacteremia
What is the method of treatment of Erysipelas?
PO or IV penicillin
What is Cellulitis?
Acute spreading infection of the skin involving subcutaneous fatty tissues (hypodermis) can lead to bacteremia, NOT raised
What are the clinical signs a person has Cellulitis?
Local: pain, erythema, edema, and warmth (no area of induration), lymphadenopathy
General: chills, fever, malaise
What skin infection is associated with these risk factors: diabetes, chronic vein stasis and previous infection?
cellulitis
If a person has been in salt water what pathogen should we suspect?
vibrio spp.
If a person has been in a hot tub or whirlpool and has developed a rash, what pathogen should we suspect?
pseudomonas aeruginosa
If a person has eaten saltwater fish, shellfish or come in contact with animal hides, what causative pathogen should we suspect?
Erysipelothrix rhusiopathiae
What is the first type of necrotizing skin infections?
type 1: mixed infection (non GAS), post-surgical setting and previously ill patients
type 2: GAS isolated alone or in combination with other bacteria (most commonly S. aureus), community acquired infection
What is the most important predisposing factor of necrotizing fasciitis?
varicella (chicken pox)
What infection is accompanied by TSS and disproportionate pain?
necrotizing fasciitis
What is the treatment for Type 1 necrotizing fasciitis?
broad spectrum coverage of both aerobes and anaerobes (IV piperacillin/tazobactam or meropenem)
What is the treatment for type 2 necrotizing fasciitis?
IV penicillin for GAS, clindamycin added to decrease toxin production
What would happen in cases meeting clinical criteria for streptococcal TSS? (hypotension, renal impairment, coagulopathy, acute respiratory distress syndrome)
IVIg
How is necrotizing fasciitis diagnosed?
surgically
What are concomitant signs of infection for necrotizing fasciitis?
fever, tachycardia, hypotension (due to shock), elevated WBC, pain
What are the 4 clues of NF?
- rapidly progressing (cm in hrs)
- pain disproportionate to apparent tissue damage
- prominent systemic symptoms/ signs
- anesthesia of affected areas (nerve ends destroyed)
What causes the rapid tissue damage observed in NF?
uncontrolled immune response causes over-production of cytokines that over-stimulate macrophages, the macrophages release massive amounts of oxygen free radicals, causing rapid tissue damage
What disease does HHV 3 cause?
Varicella (chickenpox)
What are the stages of chickenpox?
macule, papule, vesicles, pustules, then scab/crust within 4-7 days of ras onset (all happening simultaneously)
What skin infection is highly contagious (airborne and direct contact) even 1-2 days prior to rash onset?
chickenpox
What skin infection is a reactivation of herpes virus varicella-zoster, and mainly seen in stressed out yound adults?
Herpes Zoster (shingles)
What are the symptoms associated with Shingles?
fever, pain, clusters of red macules that become papules, vesicles, and then crusts; typically distributed around the trunk
What are oral antiviral agents such as acyclovir used to treat?
shingles (stop not cure)
How is HSV-1 commonly transmitted?
cold sores
How is HSV-2 commonly transmitted?
sexual contact
