export_ssti bacteria i Flashcards
Minimum diagnostic criteria for skin/soft tissue infection (SSTI)
Erythema
Edema
Warmth
Pain/tenderness
Impetigo features
Superficial
“Honey crusts”
Most commonly around the mouth
Most common bacterial infection in children
Bullous impetigo features
Blisters are cloudy, can rupture
Bullous impetigo virulence
Exfoliative toxin of S. aureus
Ecthyma
Deeper form of impetigo, scarring and ulceration
Punched-out ulcerative lesions
Furuncle (boil) causative agent
S. aureus
Furuncle features
Abscess of hair follicle
Large, painful, raised nodules
Carbuncle
Multiple furuncles that coalesce
Carbuncle defining feature
Chills and fever
Folliculitis
Infection of hair follicles
Various bacteria and fungi
Erysipelas
Acute skin infection
Involved skin is distinct from uninvolved skin
Erysipelas cause
S. pyogenes
Cellulitis
Involved skin is NOT differentiated from uninvolved skin
Paronychia
Superficial infection or abscess of nailfolds
Acute or chronic
Acute paronychia
Acutely painful abscess in nailfold
Most common cause is S. aureus
Chronic paronychia
Longer than 6 weeks
Often the result of a C. albicans infection
Necrotizing fasciitis
Destruction of muscle and fat
Toxicity, multiorgan failure, death
Antibiotics and surgical debridement
S. aureus features
Gram-positive cocci
Catalase positive
Found in skin/mucous membranes
Coagulase positive (unlike other Staph)
Beta-hemolytic
Strep. pyogenes features
Gram-positive cocci
Catalase negative
Pseudomonas aeruginosa features
Gram-negative rod
S. aureus virulence factors
Capsule
Biofilm
Teichoic acid
Protein A
Cytotoxins
Exfoliative toxins
Enterotoxins
TSST
Extracellular hydrolases
S. aureus peptidoglycan
Endotoxin-like activity
S. aureus teichoic acid
Adhesion
S. aureus protein A
Inhibits Ab mediated clearance by binding IgG Fc domain
S. aureus alpha cytotoxins
Pore-forming toxin
Allows for bacteria to get into cell, as well as resulting in lysis
S. aureus exfoliative toxins
ETA and ETB
Serine proteases that split interepidermal junctions
S. aureus enzymes
Hydrolyze host tissue to aid in the spread of the bacteria in the body
S. aureus diseases
Toxin mediated (scalded skin syndrome, food poisoning) Suppurative (impetigo, folliculitis, etc.)
S. aureus scalded skin syndome (SSSS) virulence
Caused by ETA and ETB
Important diagnostic features of SSSS
Staph not culturable from skin (toxin mediated)
No leukocytes
Nikolsky sign
Minimal pressure results in skin exfoliation
MRSA
Methicillin-resistant S. aureus
MRSA virulence factor
MecA gene
MecA gene
Encodes a new penicillin-binding protein on methicillin, etc. which results in a low affinity to the bacteria
Treat MRSA
Vancomycin
Treatment for S. aureus infections
Nafcillin
Oxacillin
Osteomyelitis
Bone pain
Fever
Swelling
Malaise
Osteomyelitis cause
Almost always by a bacterial infection
Septic arthritis features
Painful, erythematous joint with purulent material
Usually in large joints
Most common causes of septic arthritis
S. aureus in children
N. gonorrhoeae in sexually active persons