Bacterial infections of skin and soft tissue I Flashcards

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1
Q

Which pathogens are associated with diabetes?

A

S. aureus and GBS

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2
Q

Which pathogen is associated with neutropenia and hot tub use?

A

Pseudomonas aeruginosa

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3
Q

Which pathogens are associated with IV drug use?

A

MRSA, pseudomonas aeruginosa

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4
Q

Which pathogen is associated with impetigo?

A

Strep pyogenes

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5
Q

Impetigo is characterized by what type of skin lesion?

A

Honey crusted lesions and erosions often around mouth

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6
Q

Which organism is associated with bullous impetigo?

A

Staph aureus

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7
Q

What is responsible for the blisters seen in bullous impetigo?

A

Exfoliative toxin from staph aureus

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8
Q

Which organism is responsible for ecthyma?

A

Strep pyogenes

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9
Q

What type of lesion is characteristic of ecthyma?

A

Punched-out ulcerative lesions

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10
Q

Which organism is most commonly responsible for a furuncle?

A

Staph aureus

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11
Q

What is a furuncle?

A

Essentially a staph aureus abscess on a hair follicle

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12
Q

What is a carbuncle?

A

Multiple furuncles coalescing and extending deeper into subcutaneous tissues

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13
Q

What is the defining feature of a carbuncle?

A

Chills and fevers (sometimes systemic spread)

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14
Q

Which organism is typically responsible for erysipelas?

A

Strep pyogenes (recent respiratory or skin infection)

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15
Q

Cellulitis is most often caused by what organism?

A

GAS or staph aureus

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16
Q

What is paronychia?

A

Localized, superficial infection or abscess of the nailfolds, lasting longer than 6 weeks and usually secondary to candida albicans infection

17
Q

What is the most common organism associated with paronychia?

A

Staph aureus

18
Q

What is the most common cause of necrotizing fasciitis?

A

Strep pyogenes

19
Q

What are the hallmarks of necrotizing fasciitis?

A

Toxicity, multi organ failure, death

20
Q

What is the gram stain for pseudomonas?

A

Gram negative

21
Q

What is the shape of pseudomonas?

A

Rod

22
Q

What is the coagulase test for staph aureus?

A

Positive

23
Q

What is the hemolysis pattern for staph aureus?

A

Beta

24
Q

What are the structural virulence factors for staph aureus?

A

Capsule, peptidoglycan, teichoic acid, protein A

25
Q

What is the role of the staph aureus virulence factor Protein A?

A

Turns Ab around so it can no longer link to a phagocyte (non-functional presentation, soaks up Abs)

26
Q

What virulence factor mediates staphylococcal scalded skin syndrome?

A

Exfoliative toxins

27
Q

Which enzymes serve as virulence factors in staph soft tissue infections?

A

Coagulase, hyaluronidase, fibrinolysin, lipases, nucleases

28
Q

Why is staph not culturable from the skin of a SSSS patient?

A

Toxin mediated disease

29
Q

Why are leukocytes not seen on the skin of a SSSS patient?

A

No inflammation involved - only blistering

30
Q

What kind of toxins are exfoliative toxins?

A

Serine proteases

31
Q

What is the function of exfoliative toxins?

A

Split desmoglein-1 and form intercellular bridges in the stratum granulosum epidermis

32
Q

What is Nikolsky sign?

A

In SSSS - lateral pressure on fingertips leads to sloughing off of skin

33
Q

Which antibiotics are resistant to beta lactamase hydrolysis?

A

Methicillin, oxacillin, nafcillin

34
Q

What gene confers resistance of staphylococcus to methcillin?

A

MecA

35
Q

Most is the most likely bacterial cause of ostetomyelitis?

A

Staph aureus

36
Q

What is the most likely cause of septic arthritis in children and adults receiving intraarticular injections?

A

Staph aureus

37
Q

What is the most likely cause of septic arthritis in sexually active adults?

A

Neisseria gonorrhea