Infections of Skin and Soft Tissues - Clinical

Question 1

What are the three classifications of S & ST infections?

Answer 1

Exogenous - new infections, from outside
Endogenous - from previous present organism
Toxin-mediated - (i.e. S. aureus exfoliative toxin / TSST)

Question 2

What layer does impetigo infect and what are the causative organisms?

Answer 2

Epidermis

S. aureus and S. pyogenes

Question 3

What layer(s) does erysipelas infect and what are the causative organisms?

Answer 3

Dermis

S. pyogenes

Question 4

What layer(s) does cellulitis infect and what are the causative organisms?

Answer 4

Epidermis, dermis, subcutaneous

S. aureus and S. pyogenes

Question 5

What layer(s) does folliculitis infect and what are the causative organisms?

Answer 5

Outer hair follicle

S. aureus

Question 6

What layer(s) does furuncle infect and what are the causative organisms?

Answer 6

Deep in hair follicle

S. aureus

Question 7

What layer(s) does carbuncle infect and what are the causative organisms?

Answer 7

Multiple deep hair follicles in combined area

S. aureus

Question 8

What layer(s) does fasciiitis infect and what are the causative organisms?

Answer 8

Fascia

S. pyogenes, others

Question 9

What layer(s) does gas gangrene infect and what are the causative organisms?

Answer 9

Skeletal muscle

Clostrium perfringens and others

Question 10

What causes hot tub folliculitis?

Answer 10

Pseudomonas spp.

Question 11

What causes lymphatic obstruction?

Answer 11

Streptococcus species

Question 12

What bacteria enters in aquarium exposure?

Answer 12

Mycobacterium marinum

Question 13

What bacteria enters in fresh water?

Answer 13

Aeromonas species

Question 14

What bacteria enters in salt water?

Answer 14

Vibrio species (i.e. cholerae)

Question 15

What bacteria comes from animal bites? What skin symptoms can it cause?

Answer 15

Pasteurella

Can cause cellulitis progressing to gangrene / necrotizing fasciitis

Question 16

What disease is commonly spread via the fingers of HCW?

Answer 16

Herpes simplex

Question 17

What is the causative agent of ecthyma gangrenosum?

Answer 17

P. aeruginosa, in neutropenic patients

Question 18

How does impetigo differ between Staph and Strept?

Answer 18

Staph - boil / localized

Strept = honey-crust

Question 19

What patient population is cellulitis particularly common in?

Answer 19

Diabetics - due to anaerobes fermenting their sugar (especially during neuropathy)

Question 20

What population of patients is susceptible to cutaneous candidiasis and where does it occur?

Answer 20

Diabetics, occurs in sweaty / moist areas (skin folds)

Question 21

Where does tinea versicolor occur?

Answer 21

Trunk or extremities

Question 22

Where is tinea cruris?

Answer 22

The groin

Question 23

What are the three fungal genera causing tinea infections?

Answer 23

Trichophyton
Epidermophyton
Microsporum

Question 24

What is an endogenous infection?

Answer 24

An infection caused by an infectious agent that is already present in the body, but has previously been inapparent or dormant

Question 25

What are two routes of endogenous skin and soft tissue infection?

Answer 25

1. Direct extension - i.e. Herpes simplex activates to skin from the nerve, or draining nasal sinus seeds pathogen to bone
2. Hematogenous - IV line displaces pathogens throughout bloodstream, allowing spread to soft tissues (i.e. endocarditis)

Question 26

What is secondary syphilis?

Answer 26

The second stage of syphilis, with lesions around the body, especially palms and soles

Question 27

Define exanthem. What diseases is this common in?

Answer 27

A widespread rash, common in measles and german measles, as well as chicken pox

Question 28

What type of skin finding do herpes infections have?

Answer 28

Vesicles
Labialis: lips
Genitalis: ulcers
Zoster: Dermatomal

Question 29

What type of skin lesions are present with hand, foot, and mouth disease?

Answer 29

Vesicles (blisters)

*Cocksackie virus

Question 30

What causes scarlet fever?

Answer 30

erythogenic toxin of S. pyogenes, causing spotted lesions around body

Question 31

What is used to treat a CA-MRSA infectino causing a boil?

Answer 31

Always drain / lance boils

Give oral TMP/SMX, clindamycin (good for staph, strept, and anaerobes), doxycycline (good for CA-MRSA)