Skin and Soft Tissue Infections

Question 1

Viral warts causative agent

Answer 1

HPV

Question 2

What are pilondial cysts?

Answer 2

Cysts in natal cleft, contain hair / debris / pus

Question 3

Impetigo causative agent

Answer 3

S. Aureus

Question 4

Erysipelas: description and causative agent

Answer 4

Raised, demarcated rash all over face

S. Pyogenes

Question 5

Cellulitis: definition and causative agents

Answer 5

Infection of dermis + subcutaneous fat

S. aureus, S. progenies, B-haemolytic strep

Question 6

Orbital cellulitis

Answer 6

Infection of soft tissue around eye
Spreads from skin / sinuses / blood / trauma
Eryhtmea, pain, swelling, bulging

Question 7

Ectyma gangranosum: description and causative agent

Answer 7

Erythema –> necrosis –> ulceration.

P. aeruginosa, only seen in immunosuppressed

Question 8

Pyoderma gangrenosum: Description and aetiology

Answer 8

Progressive necrosis of skin results in ulceration.

Non-infectious: autoimmune

Question 9

Type 1 Necrotising Fasciitis

Answer 9

Polymicrobial. Gram -ve, strep, anaerobes. Colonise ischaemic tissue to cause necrosis.
RF: DM, obesity, immunosuppression, alcohol, age.

Question 10

Type 2 Necrotising Fasciitis

Answer 10

Group A strep mediated. Younger, associated with trauma to skin.
Infection –> toxin release –> disruption of blood supply –> necrosis

Question 11

Gangrene

Answer 11

Necrosis caused by poor blood supply. Wet / dry / gas. Staph, strep, BNB, anaerobes,

Question 12

Diabetic foot infection causative agents

Answer 12

S. aureus, strep, corynebacterium, GNB, anaerobes

Question 13

Osteomyletis aetiology

Answer 13

Contiguous: diabetic foot infection
Haematogenous
Penetrating

Question 14

Prosthetic joint infection mechanism

Answer 14

Organisms on surface of foreign body and establish biofilm. S. aureus, S, epidermis, propionibacteria.