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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
Erysipelas - causative agent
S. pyogenes
26
Erysipelas - history
often occurs at site of skin damage face or shin preceded by pain & tenderness
27
Erysipelas - examination
fever and malaise well-demarcated inflamed lesion - red, swollen, painful and hot lymph node enlargement
28
Erysipelas - diagnosis
clinical diagnosis | culture rarely helpful (will not grow)
29
Cellulitis - causative agents
S.aureus S.pyogenes Pasteurella multocida (animal bites) Haemophilus influenzae
30
Cellulitis - history
site of skin penetration | any part of body
31
Cellulitis - examination
fever and malaise | diffuse inflamed lesion: erythema, swelling, tenderness, heat
32
Cellulitis - diagnosis
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
Anthrax - causative factor
Bacilus anthracis - spore-forming aerobic gram+ve bacillus
34
Anthrax - where from?
acquired from imported wool, hair and animal hides
35
Anthrax - epidemiology
woolsorters' disease | West African drum skin makers and injecting drug use
36
Anthrax - patterns of disease
Cutaneous anthrax (mortality
37
Necrotising fasciitis -
infection of skin and subcut tissues
38
Necrotising fasciitis - causative agents
Type one: polymicrobial - enteric gram -ve bacilli anaerobes Type two: strep. pyogenes
39
Necrotising fasciitis - history
spontaneous or at site of skin penetration for any part of the body
40
Necrotising fasciitis - examination
fever and malaise dark, rapidly spreading, necrotic lesion
41
Necrotising fasciitis - diagnosis
microscopy and culture Debrided material and blood culture
42
Necrotising fasciitis - treatment
IV ATX | surgical debridement
43
Anaerobic infections
Uncommon due to availability of O2
44
Anaerobic infections - gas gangrene
clinically similar to synergistic gangrene palpable cutaneous gas usually post op infection
45
Anaerobic infections - causative agent
Clostridium perfringens (anaerobic gram+ve bacillus)
46
Anaerobic infections - treatment
IV antibiotics | Surgical debridement
47
Empiric therapy for Staph. aureus or pyogenes
Flucloxacillin (with fusidic acid or mupirocin or impetigo) Penicillin alergy: erythromycin + clarithromycin; vancomycin; linezolid
48
Empiric therapy for necrotising fasciitis
need to cover anaerobes, enterobacteriaceae, strepcocci and staphylococci drugs: meropenem + clindamycin
49
Empiric therapy for anaerobic infections
anti-anaerobic agents e.g. metronidazole
50
Empiric therapy for high risk for MRSA
vancomycin, linezolid
51
Dermatophyte infections - skin
Tinea corporis, tinea pedis (athletes foot), tinea cruris
52
Dermatophyte infections - nails
Onychomycosis
53
Dermatophyte infections - scalp
tinea capitis (scalp ringworm, kerion)
54
Dermatophyte infections - causative agents
Tricophyton spp. | Microsporum spp.
55
Dermatophyte infections - pathogenesis
Dermatophyte use keratin as nutritional substrate Usually restricted to stratum corneum Rarely penetrate the living cells of the epidermis
56
Dermatophyte infections - diagnosis
skin scrapings - microscopy and culture
57
Dermatophyte infections - treatment
topical or systemic antifungal agents
58
Topical antifungal agents
Clotrimazole, terbinafine
59
Systemic antifungal therapy
For scalp and nail infections Terbinafine, itraconazole, griseofulvin

Clinical Pathology (65 decks)

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