62 Skin + soft tissue infections Flashcards Preview

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Flashcards in 62 Skin + soft tissue infections Deck (27)
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1
Q

Which organisms typically colonise the skin? (4)

A

Coagulase negative staphylococci.
Staph aureus.
Propionibacterium spp.
Corynebacterium spp.

2
Q

Which viruses cause skin infections? (6)

A
Herpes simplex virus.
Herpes zoster virus.
Molluscum contagiosum.
Human Papilloma virus.
Orf.
Cowpox.
3
Q

What kind of skin infection does HSV cause?

A

1o: painful + extensive lesions inside mouth.
2o: perioral weeping + vesicular lesions.

4
Q

How is Herpes Simplex diagnosed?

A

Clinical.

Difficult cases: vesicle fluid PCR.

5
Q

How is HSV treated?

A

Cold sores: topical acyclovir.

Genital herpes: oral acyclovir.

6
Q

How does herpes zoster infection present?
Diagnosis?
Treatment?

A

Weeping vesicular rash with dermatomal distribution.
Clinical.
Aciclovir/valaciclovir.

7
Q

What causes molluscum contagiosum?

A

The pox virus.

8
Q

Appearance of molluscum contagious infection?
Diagnosis?
Treatment?

A

Raised pearly lesions up to 3mm. Umbilicated.
Clinical.
None - physical rx if disfiguring.

9
Q

Which virulence factors does staph aureus produce? (3)

A

DNAase,
Coagulase,
Teichoic acid.

10
Q

Which exotoxins does staph aureus produce? (3)

A

Epidermolytic toxins A + B
Toxic Shock Syndrome Toxin.
Pantun-Valentine leukocidin.

11
Q

Which virulence factors does s pyogenes produce? (7)

A
Adhesins
M proteins
Hyaluronic acid capsule
Hyaluronidase
C5a peptidase
Streptolysins O and S 
Pyogenic exotoxins
12
Q

What is impetigo?
Causes? (2)
Lesion appearance?

A

Infection of the epidermis. (Often at site of skin damage).
Staph aureus, Strep pyogenes.
Plaque like, yellowish, thick “honey crusted”

13
Q

What are the complications of an impetigo infection?

Pathogenesis?

A

Bullous impetigo, Staphylococcal Scalded Skin Syndrome.

Epidermolytic toxins inactivate glycoprotein desmoglein-1 (required for cell-cell adhesion).

14
Q

What is erysipelas?
Causative agent?
History?

A

Infection of the dermis.
Strep pyogenes.
At skin damage site, often face/neck. Preceeded by pain.

15
Q

What is seen on examination in erysipelas? (3)

A

Fever, malaise.
Well demarcated inflamed lesion (red + hot).
Lymph node enlargement.

16
Q

What is cellulitis?

Causative agents? (4)

A
Infection of the skin and subcutaneous tissue.
Staph aureus.
Strep pyogenes.
Pasteurella multocida.
Haemophilus influenzae.
17
Q

What is seen on examination in cellulitis?

A

Fever, malaise.

Diffuse inflamed lesion.

18
Q

Anthrax organism?
Appearance?
Epidemiology?
Sites of infection?

A

Bacillus anthracis.
Malignant pustule/ eschar (black).
West African drum use, IVDU’s.
Cutaneous ( 1% mortality) vs inhlational/septicaemic (45% mortality).

19
Q

What are the causes of necrotising fasciitis?

A

Type 1: Polymicrobial: anaerobes, enteric gram -ve bacilli.

Type 2: Strep pyogenes.

20
Q

Necrotising fasciitis: examination:
Diagnosis:
Treatment:

A

Fever, malaise, dark rapidly spreading necrotic lesion.
Rx on suspicion, but microscopy + culture.
IV meropenem + clindamycin + surgical debridement.

21
Q

Gas gangrene. Organism:
Examination:
History:
Rx:

A
Clostridium perfringens (anaerobic g+ve bacillus).
Palpable subcutaneous gas. Dark + necrotic lesion.
Post operative (lower GI or amputees).
IV antibiotics (metronidazole) + surgical debridement.
22
Q

What is the empiric therapy for skin infections?

A

Flucloxacillin.

Pen allergy: eryro/claryhtromycin, vacomcin, linezolid.

23
Q

How are high MRSA risk skin infections treated? (2)

A

Vancomycin.

Linezolid.

24
Q

Causative agents of dermatophyte infections? (2)

Pathogenesis:

A

Tricophyton spp. Microsporum spp.

Keratin = nutritional substrate. Restricted to stratum corneum, rarely penetrate living cells.

25
Q

How are dermatophyte infections diagnosed?

A

Microscopy + culture of skin scrapings.

26
Q

How are fungal skin infections treated? (2)

A

Topical antifungals:

Clotrimazole. Terbinafine.

27
Q

How are fungal scalp and nail infections treated? (3)

A

Systemic antifungals:

Terbinafine. Itraconazole. Griseofulvin.

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