Approach to secondary skin infections Flashcards
How are commensals involved in skin infections?
- 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
What are the most common commensal skin bacteria and fungi?
Bacteria = S.pseudointermedius Fungi = Malassezia pachydermatis
In comparison to commensals, infections with pathogens are diagnosed …?
On cultrue
What are the pathogens causing bacterial pyoderma? Which is the most common?
Commensal bacteria from mucosae or gastro-intestinal tract
Staphylococcus pseudintermedius
What are some examples of underlying disease causes of bacterial pyoderma?
- Allergy
- Ectoparasites
- Immune deficiency
- Keratinisation defects
What are the 3 classifications of bacterial pyoderma?
- Surface: superficial epidermis
- Superficial: epidermis and hair follicles
- Deep: epidermis, hair follicles, dermis +/- subcutaneous fat
What are the 3 clinical presentations of surface bacterial pyoderma?
- ‘Hotspots’ = pyotraumatic dermatitis (PTD)
- Skin fold pyoderma = intertrigo
- Bacterial overgrowth
Describe ‘Hotspots’ = pyotraumatic dermatitis (PTD)
- 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
Which 3 dog breeds are predisposed to ‘Hotspots’?
Rottweiler
Golden retriever
German shepherd
How are hotspots treated?
Clip (often need sedation), clean, topical antiseptic/antimicrobial, and systemic/topical anti-inflammatory e.g., steroids
Intertrigo is also called?
Skin fold pyoderma
Why/how does skin fold pyoderma occur?
- Compromised skin barrier: friction, loss of ventilation, fluid accumulation
- Microbes proliferate and produce toxins which creates inflammation
- Erythema and moist exudate
How is skin fold pyoderma treated?
Topical antiseptics/ anti-microbial & topical/systemic anti-inflammatories. Other e.g., weight loss in obese dogs causing a deep vulvar fold
Bacteria overgrowth is common in dogs with which condition?
Atopic dermatitis
What are the signs of bacteria overgrowth?
- Affects the ventral trunk and interdigital spaces
- Pruritic
- Erythema, hyperpigmentation, lichenification, excoriation & alopecia
Malassezia overgrowths occurs secondary to?
Underlying disease
What sample technique would be used for dry, erythematous, scaly, alopecic patch on the neck?
Acetate tape strip
What sample technique would be used for greasy, brown wax between digits?
Indirect smear using a cotton bud
What is the most common presentation of superficial pyoderma?
Bacteria folliculitis
Describe the features of bacterial folliculitis
- papules and pustules
- pyogenic = degenerative neutrophils & phagocytosis of bacteria
- Pruritic or non-pruritic
Which bacteria are the main cause of bacterial folliculitis?
Staphylococcus pseudintermedius
What are the clinical signs of bacteria folliculitis?
- Erythema, follicular papules & pustules, crusts, epidermal collarettes, erosions
- Annular macules of alopecia “moth eaten”
- Hyperpigmented / lichenified plaques if chronic
Which skin structures are involved in deep pyoderma?
- Epidermis
- Entire hair follicle
- Follicles rupture
- Dermis +/- subcutaneous fat
What are the features of deep pyoderma?
Heat, swelling, erythema, furuncles, nodules, bullae, plaques, sinus tracts, ulcers, exudation and crusts
