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Y3 MOD Dermatology > Approach to secondary skin infections > Flashcards

Approach to secondary skin infections Flashcards

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Dermatology Board Prep flashcards
1
Q

How are commensals involved in skin infections?

A
  • Skin infection is usually associated with commensal (bacterial and/or fungal) organisms
  • Commensals take advantage of either a problem with the skin barrier and/or the skin or systemic immune system
  • Culture for these organisms is not diagnostic as they are present on the skin anyway
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2
Q

What are the most common commensal skin bacteria and fungi?

A 
Bacteria = S.pseudointermedius
Fungi = Malassezia pachydermatis
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3
Q

In comparison to commensals, infections with pathogens are diagnosed …?

A

On cultrue

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4
Q

What are the pathogens causing bacterial pyoderma? Which is the most common?

A

Commensal bacteria from mucosae or gastro-intestinal tract

Staphylococcus pseudintermedius

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5
Q

What are some examples of underlying disease causes of bacterial pyoderma?

A
  • Allergy
  • Ectoparasites
  • Immune deficiency
  • Keratinisation defects
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6
Q

What are the 3 classifications of bacterial pyoderma?

A
  • Surface: superficial epidermis
  • Superficial: epidermis and hair follicles
  • Deep: epidermis, hair follicles, dermis +/- subcutaneous fat
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7
Q

What are the 3 clinical presentations of surface bacterial pyoderma?

A
  1. ‘Hotspots’ = pyotraumatic dermatitis (PTD)
  2. Skin fold pyoderma = intertrigo
  3. Bacterial overgrowth
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8
Q

Describe ‘Hotspots’ = pyotraumatic dermatitis (PTD)

A
  • Lesions that develop within in a few hours due to self trauma
  • Lesions on cheek, neck or rump
  • Well-demarcated patch of alopecia, central erosion, peripheral erythematous halo e.g., underlying flea allergy
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9
Q

Which 3 dog breeds are predisposed to ‘Hotspots’?

A

Rottweiler
Golden retriever
German shepherd

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10
Q

How are hotspots treated?

A

Clip (often need sedation), clean, topical antiseptic/antimicrobial, and systemic/topical anti-inflammatory e.g., steroids

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11
Q

Intertrigo is also called?

A

Skin fold pyoderma

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12
Q

Why/how does skin fold pyoderma occur?

A
  • Compromised skin barrier: friction, loss of ventilation, fluid accumulation
  • Microbes proliferate and produce toxins which creates inflammation
  • Erythema and moist exudate
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13
Q

How is skin fold pyoderma treated?

A

Topical antiseptics/ anti-microbial & topical/systemic anti-inflammatories. Other e.g., weight loss in obese dogs causing a deep vulvar fold

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14
Q

Bacteria overgrowth is common in dogs with which condition?

A

Atopic dermatitis

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15
Q

What are the signs of bacteria overgrowth?

A
  • Affects the ventral trunk and interdigital spaces
  • Pruritic
  • Erythema, hyperpigmentation, lichenification, excoriation & alopecia
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16
Q

Malassezia overgrowths occurs secondary to?

A

Underlying disease

17
Q

What sample technique would be used for dry, erythematous, scaly, alopecic patch on the neck?

A

Acetate tape strip

18
Q

What sample technique would be used for greasy, brown wax between digits?

A

Indirect smear using a cotton bud

19
Q

What is the most common presentation of superficial pyoderma?

A

Bacteria folliculitis

20
Q

Describe the features of bacterial folliculitis

A
  • papules and pustules
  • pyogenic = degenerative neutrophils & phagocytosis of bacteria
  • Pruritic or non-pruritic
21
Q

Which bacteria are the main cause of bacterial folliculitis?

A

Staphylococcus pseudintermedius

22
Q

What are the clinical signs of bacteria folliculitis?

A
  • Erythema, follicular papules & pustules, crusts, epidermal collarettes, erosions
  • Annular macules of alopecia “moth eaten”
  • Hyperpigmented / lichenified plaques if chronic
23
Q

Which skin structures are involved in deep pyoderma?

A
  • Epidermis
  • Entire hair follicle
  • Follicles rupture
  • Dermis +/- subcutaneous fat
24
Q

What are the features of deep pyoderma?

A

Heat, swelling, erythema, furuncles, nodules, bullae, plaques, sinus tracts, ulcers, exudation and crusts

25
Q

What are furuncles?

A

Skin abscesses caused by staphylococcal infection, which involve a hair follicle and surrounding tissue

26
Q

Which type of inflammation is involved in deep pyoderma?

A

Pyogranulomatous inflammation

- Neutrophils, macrophages +/- eosinophils

27
Q

What is diagnostic for pyoderma?

A

Cytology

28
Q

What are the 4 different cytology techniques?

A
  • Direct impression smear (DIS)
  • Cotton tip/swab smear (IDS)
  • Adhesive tape strip (ATS)
  • Fine needle aspirate (FNA)
29
Q

What is the key finding on cytology to confirm pyoderma?

A

Degenerative neutrophils and intracellular bacteria is the key finding
- In most cases S. pseudintermedius

30
Q

In which cases is it appropriate to perform culture and sensitivity?

A
  • Recurrent or chronic infection
  • Rod-shaped or unusual organisms on cytology
  • Degenerate neutrophils but absence of bacteria on cytology
  • Deep infections
  • Non-healing wounds
  • Life threatening infections
31
Q

What is the culture technique for superficial infections?

A
  • Rupture and sample intact lesion if present

- Sample erosion under a crust or at the edge of a collarette

32
Q

What is the culture technique for deep infections?

A
  • Fresh tissue sample (biopsy)
  • Rupture intact lesion if possible and use swab (not if suspect mycobacteria)
  • Swab into deep sinus tract (last resort)
33
Q

How should confirmed bacterial pyoderma be treated?

A
  • Investigate & treat the underlying primary disease
  • Use topical treatment in every case where possible
    +/- Systemic antimicrobials IF NEEDED
34
Q

What is the most common antiseptic used in skin, give examples of forms it comes in

A

Chlorhexidine

  • Shampoos
  • Sprays
  • Gels
  • Wet wipes
  • Mouse
35
Q

What is the first line treatment for Malassezia?

A

Chlorhexidine

36
Q

If systemic antibiotics are needed for pyoderma, how to select?

A
  • If first time pyoderma, groups of cocci on cytology, and no risk factors for AMR, treatment can be selected empirically
  • However, Meticillin Resistant S. pseudintermedius (MRSP) are emerging which are resistant to β-lactams and usually fluoroquinolones
37
Q

What are the risk factors of Meticillin Resistant S. pseudintermedius (MRSP)?

A
  • Hospital admission

- Multiple vet visits

38
Q

If antibiotics are needed for pyoderma, what duration for superficial and deep?

A 
Superficial = 2-3weeks
Deep = 4-12 weeks

Y3 MOD Dermatology (12 decks)

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