Bacterial infections of skin and soft tissue I Flashcards
Which pathogens are associated with diabetes?
S. aureus and GBS
Which pathogen is associated with neutropenia and hot tub use?
Pseudomonas aeruginosa
Which pathogens are associated with IV drug use?
MRSA, pseudomonas aeruginosa
Which pathogen is associated with impetigo?
Strep pyogenes
Impetigo is characterized by what type of skin lesion?
Honey crusted lesions and erosions often around mouth
Which organism is associated with bullous impetigo?
Staph aureus
What is responsible for the blisters seen in bullous impetigo?
Exfoliative toxin from staph aureus
Which organism is responsible for ecthyma?
Strep pyogenes
What type of lesion is characteristic of ecthyma?
Punched-out ulcerative lesions
Which organism is most commonly responsible for a furuncle?
Staph aureus
What is a furuncle?
Essentially a staph aureus abscess on a hair follicle
What is a carbuncle?
Multiple furuncles coalescing and extending deeper into subcutaneous tissues
What is the defining feature of a carbuncle?
Chills and fevers (sometimes systemic spread)
Which organism is typically responsible for erysipelas?
Strep pyogenes (recent respiratory or skin infection)
Cellulitis is most often caused by what organism?
GAS or staph aureus
What is paronychia?
Localized, superficial infection or abscess of the nailfolds, lasting longer than 6 weeks and usually secondary to candida albicans infection
What is the most common organism associated with paronychia?
Staph aureus
What is the most common cause of necrotizing fasciitis?
Strep pyogenes
What are the hallmarks of necrotizing fasciitis?
Toxicity, multi organ failure, death
What is the gram stain for pseudomonas?
Gram negative
What is the shape of pseudomonas?
Rod
What is the coagulase test for staph aureus?
Positive
What is the hemolysis pattern for staph aureus?
Beta
What are the structural virulence factors for staph aureus?
Capsule, peptidoglycan, teichoic acid, protein A
What is the role of the staph aureus virulence factor Protein A?
Turns Ab around so it can no longer link to a phagocyte (non-functional presentation, soaks up Abs)
What virulence factor mediates staphylococcal scalded skin syndrome?
Exfoliative toxins
Which enzymes serve as virulence factors in staph soft tissue infections?
Coagulase, hyaluronidase, fibrinolysin, lipases, nucleases
Why is staph not culturable from the skin of a SSSS patient?
Toxin mediated disease
Why are leukocytes not seen on the skin of a SSSS patient?
No inflammation involved - only blistering
What kind of toxins are exfoliative toxins?
Serine proteases
What is the function of exfoliative toxins?
Split desmoglein-1 and form intercellular bridges in the stratum granulosum epidermis
What is Nikolsky sign?
In SSSS - lateral pressure on fingertips leads to sloughing off of skin
Which antibiotics are resistant to beta lactamase hydrolysis?
Methicillin, oxacillin, nafcillin
What gene confers resistance of staphylococcus to methcillin?
MecA
Most is the most likely bacterial cause of ostetomyelitis?
Staph aureus
What is the most likely cause of septic arthritis in children and adults receiving intraarticular injections?
Staph aureus
What is the most likely cause of septic arthritis in sexually active adults?
Neisseria gonorrhea
