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Clinical Pathology > 62 - Skin and Soft Tissue Infection > Flashcards

62 - Skin and Soft Tissue Infection Flashcards

1
Q

What bacteria on skin?

A

Coagulase-negative staphylococci
Staph. aureus
Propionibacterium
Corynebacterium spp.

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2
Q

Molluscum contagiosum causes

A

a skin infection

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3
Q

Apparently, need to look up

A

HPV, Orf, Cowpox

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4
Q

Herpes simplex - pathogenesis

A
  1. virus gains entry via sensory nerve endings and migrates to dorsal root ganglion
  2. viral DNA exists as episomes and no virus-coded proteins are present to stimulate an immune resopnse
  3. reactivated and migrates back out to sensory nerve ending and causes clinical manifestation
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5
Q

Herpes simplex - clinical presentation

A

Triggered e.g. by infection or stress

Primary (infants) - extensive, painful lesions also inside mouth (but rarely seen as not there long)

Secondary (all ages) peri-oral (genital), weeping, vesicular

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6
Q

Herpes simplex - diagnosis

A

Vesicle fluid - PCR for herpes virus DNA, immunofluorescence, culture

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7
Q

Herpes simplex - treatment

A

Cold sores - topical acyclovir

Genital herpes - oral acyclovir

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8
Q

Herpes zoster - history

A

previous chickenpox

triggered by physical or emotional insult preceded by tingling and/or pain

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9
Q

Herpes zoster - examination

A

weeping, vesicular rash

dermatomal distribution

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10
Q

Herpes zoster - treatment

A

oral aciclovir/valaciclovir
IV aciclovir
seek specialist advice if needed

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11
Q

Molluscum contagiosum - causative agent

A

molluscum contagiosum virus - poxvirus

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12
Q

Molluscum contagiosum - examination

A

raised, pearly lesions up to 3mm which are umbilicated

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13
Q

Molluscum contagiosum - diagnosis

A

clinical

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14
Q

Molluscum contagiosum - treatment

A

none - lesions usually disappear in 6-18 months

various topical preps + physical treatments

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15
Q

Bacterial infections - causative agents

A

Staph. aureus

Group A B-haemolytic streptococci (S. pyogenes)

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16
Q

S.aureus

A

Gram +ve cocci in clumps
Normal nasal flora in 30% of people
Large # of virulence factors e.g. DNAse, coagulase, teichoic acid

Exotoxins: epidermolytic toxins, toxic shock syndrome toxin, Panton-valentine leukocidin

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17
Q

S.pyogenes

A

Gram +ve cocci in chains

Express many virulence factors: adhesins, M proteins, hyaluronic acid capsule, hyaluronidase, C5a peptidase, Streptolysins O and S, pyrogenic exotoxins

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18
Q

Impetigo

A

Infection of epidermis (superficial)

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19
Q

Impetigo - causative agent

A

S. aureus, S.pyogenes

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20
Q

Impetigo - history

A

often occurs at site of skin damage

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21
Q

Impetigo - examination

A

plaque-like lesions with yellowish exudate.

thick scabs called honey crusted lesions

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22
Q

Impetigo - diagnosis

A

clinical diagnosis and bacterial culture

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23
Q

Impetigo - complications

A

Epidermolytic toxin production (ETA & ETB)

Manifests as localised ‘bullous impetigo’

or general: staph. scalded skin syndrome (SSSS) - looks like burned skin

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24
Q

Erysipelas - where does it infect

A

Infection of dermis - deeper than superficial

25
Q

Erysipelas - causative agent

A

S. pyogenes

26
Q

Erysipelas - history

A

often occurs at site of skin damage

face or shin

preceded by pain & tenderness

27
Q

Erysipelas - examination

A

fever and malaise

well-demarcated inflamed lesion - red, swollen, painful and hot

lymph node enlargement

28
Q

Erysipelas - diagnosis

A

clinical diagnosis

culture rarely helpful (will not grow)

29
Q

Cellulitis - causative agents

A

S.aureus
S.pyogenes
Pasteurella multocida (animal bites)
Haemophilus influenzae

30
Q

Cellulitis - history

A

site of skin penetration

any part of body

31
Q

Cellulitis - examination

A

fever and malaise

diffuse inflamed lesion: erythema, swelling, tenderness, heat

32
Q

Cellulitis - diagnosis

A

Clinical
Broad differential
Microbiology - lesion swabs (85% +ve)

Lesion aspirates and skin biopsy (20%) - not recommended routinely

Blood cultures (positive in only 2-4% of cases) only if severe sepsis or systemic signs of infection

33
Q

Anthrax - causative factor

A

Bacilus anthracis - spore-forming aerobic gram+ve bacillus

34
Q

Anthrax - where from?

A

acquired from imported wool, hair and animal hides

35
Q

Anthrax - epidemiology

A

woolsorters’ disease

West African drum skin makers and injecting drug use

36
Q

Anthrax - patterns of disease

A

Cutaneous anthrax (mortality

37
Q

Necrotising fasciitis -

A

infection of skin and subcut tissues

38
Q

Necrotising fasciitis - causative agents

A

Type one: polymicrobial - enteric gram -ve bacilli
anaerobes

Type two: strep. pyogenes

39
Q

Necrotising fasciitis - history

A

spontaneous or at site of skin penetration for any part of the body

40
Q

Necrotising fasciitis - examination

A

fever and malaise

dark, rapidly spreading, necrotic lesion

41
Q

Necrotising fasciitis - diagnosis

A

microscopy and culture

Debrided material and blood culture

42
Q

Necrotising fasciitis - treatment

A

IV ATX

surgical debridement

43
Q

Anaerobic infections

A

Uncommon due to availability of O2

44
Q

Anaerobic infections - gas gangrene

A

clinically similar to synergistic gangrene

palpable cutaneous gas

usually post op infection

45
Q

Anaerobic infections - causative agent

A

Clostridium perfringens (anaerobic gram+ve bacillus)

46
Q

Anaerobic infections - treatment

A

IV antibiotics

Surgical debridement

47
Q

Empiric therapy for Staph. aureus or pyogenes

A

Flucloxacillin (with fusidic acid or mupirocin or impetigo)

Penicillin alergy: erythromycin + clarithromycin; vancomycin; linezolid

48
Q

Empiric therapy for necrotising fasciitis

A

need to cover anaerobes, enterobacteriaceae, strepcocci and staphylococci

drugs: meropenem + clindamycin

49
Q

Empiric therapy for anaerobic infections

A

anti-anaerobic agents e.g. metronidazole

50
Q

Empiric therapy for high risk for MRSA

A

vancomycin, linezolid

51
Q

Dermatophyte infections - skin

A

Tinea corporis, tinea pedis (athletes foot), tinea cruris

52
Q

Dermatophyte infections - nails

A

Onychomycosis

53
Q

Dermatophyte infections - scalp

A

tinea capitis (scalp ringworm, kerion)

54
Q

Dermatophyte infections - causative agents

A

Tricophyton spp.

Microsporum spp.

55
Q

Dermatophyte infections - pathogenesis

A

Dermatophyte use keratin as nutritional substrate

Usually restricted to stratum corneum

Rarely penetrate the living cells of the epidermis

56
Q

Dermatophyte infections - diagnosis

A

skin scrapings - microscopy and culture

57
Q

Dermatophyte infections - treatment

A

topical or systemic antifungal agents

58
Q

Topical antifungal agents

A

Clotrimazole, terbinafine

59
Q

Systemic antifungal therapy

A

For scalp and nail infections

Terbinafine, itraconazole, griseofulvin

Clinical Pathology (65 decks)

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