Bacterial Skin Infections Flashcards
Folliculitis:
Pyogenic infection in the hair follicles.
Furuncles:
Boils, extension of folliculitis.
Carbuncles:
Infection extends to the deeper subcutaneous tissue with a single inflammatory mass.
Spreading infection confined to the epidermis:
Impetigo
Spreading infection involving the dermal lymphatics:
Erysipelas
Cellulitis:
When the major factor is the subcutaneous fat layer.
Macules:
Flat, non-palpable lesions.
Papules:
Palpable lesions.
Vesicles:
Palpable, fluid filled lesions.
Pustules:
Palpable and contain pus.
Bulla:
Collection of serous fluid and have small numbers of inflammatory cells.
Common cause of impetigo (2):
- Strep pyogenes
- Staph aureus
Common cause of erysipelas:
Strep pyogenes
Common cause of folliculitis, furuncles and carbuncles:
Staph aureus
Common cause of necrotizing fasciitis:
Anaerobes and microaerophiles, usually mixed infections.
Common cause of myonecrosis gangrene:
Clostridium perfringens
Skin manifestation of Salmonella:
“Rose spots” containing bacteria.
Skin manifestation of pseudomonas:
Ecthyma gangrenosum
Skin manifestation of strep pyogenes:
Erythematous rash (toxin)
Skin manifestation of Staph aureus:
Rash and desquamation (toxin)
Virulence factors of S. aureus (5):
- Staph toxins
- Exfoliative toxins
- Enterotoxins
- Toxic shock syndrome toxins
- Enzymes
Impetigo (4):
- Contagious superficial infection
- Primarily seen in young children
- Purulent with crusting
- Caused by strep pyogenes +/- staph aureus
Pustular impetigo (4):
- Intraepidermal vesicles filled with exudate.
- Crusted lesions
- Caused by strep pyogenes or staph aureus
- Seen in exposed areas of the body during warm, moist weather
Bullous impetigo (5):
- Localized staph scalded skin syndrome
- Caused by staph aureus that produces exfoliative toxin A
- Newborns and young children
- Culture positive
- No Nikolsky’s sign
Erysipelas (4):
- Tender, superficial erythematous and edematous lesions
- Spreads primarily in upper dermis and superficial lymphatics
- Mainly young and elders
- Caused by strep pyogenes
Majority of cellulites is caused by:
Strep pyogenes and staph aureus
Necrotizing fasciitis:
Deep seated infection of the subcutaneous tissue leading to destruction of fascia and fat, but may spare skin.
Type I necrotizing fasciitis:
Mixed infection caused by aerobic and anaerobic bacteria.
Occurs most commonly after surgical procedures, DM, and PVD.
Type II necrotizing fasciitis:
Caused by strep pyogenes or staph aureus.
Necrotizing fasciitis caused by v. vulnificus:
Rapidly progressive wound infections after exposure to contaminated sea water.
Myonecrosis:
Necrotizing infection of muscle.
Staph scalded skin syndrome (4):
Ritter’s disease
- Perioral erythema covers entire body w/in 2 days
- Positive Nikolsky’s sign
- Large blister with clear fluid, no organism, no leukocytes
- Exfoliative toxin destroys the intracellular connections in the skin
Mycobacterium leprae (2):
- An obligately aerobic rod with Gram positive-like cell wall
- Grow best in skin histocytes, endothelial cells and schwann cells
Treatment for lepromatous leprosy:
Triple therapy with dapsone, ribiospfampin and clofazimine x 2 years.
Treatment for tuberculoid leprosy:
Dapsone and rifampin for 6 months.
Bacillus anthracis (3):
- Gram positive, spore forming
- Capsule
- Exotoxin:
- Edema factor
- Lethal factor
- Protective antigen
Lethal factor:
A protease that induces macrophage to produce high levels of cytokines that trigger the shock.
Inhalation anthrax (3):
- Inhalation of aerosolized spores
- Mediastinal widening
- Replication occurs within the lung with local exotoxin release.
