Approach to secondary skin infection Flashcards
What presenting sign would a bacterial infection have?
- Pustules
- Crust
- Scale
- Alopecia
- Variable pruritus
- Nodules (if deep infection)
What presenting signs would Malassezia have?
- Scale +++
- Variable pruritus
What is the most common commensal bacteria + fungi?
*Staph. pseudintermedius
*Malassezia pachydermatis
What are underlying diseases for commensal skin infections?
*Allergy e.g., cAD
* Ectoparasites
* Self trauma
– pain
* Other infections
- dermatophytosis
- leishmaniasis
* Immune deficiency
– endocrinopathy
– chemotherapy
– drug induced
* Keratinisation defects
* Follicular dysplasia
* Environment / hygiene issues
* Anatomical defects
* Metabolic disease
* Iatrogenic
- post-grooming (Pseudomonas)
- maceration
* Neoplasia
What bacteria cause pyoderma?
- Staphylococcus pseudintermedius
– most common - S. aureus, S. schleiferi and S. canis
– less common - Gram-negative or atypical bacteria
– E.g., E. coli, Proteus spp., Pseudomonas spp.
– uncommon to rare
What is an example of primary skin pathogens?
*Dermatophytes
Bacterial pyoderma can be classified on the depth of infection, what are the 3 classes?
1.Surface
– Superficial epidermis
– Overgrowth NOT infection as NOT pyogenic
2. Superficial
– Epidermis and hair follicles
3. Deep
– Epidermis, hair follicles, dermis +/- subcutaneous fat
What are the clinical presentations for surface infection?
- ‘Hotspots’ = pyotraumatic dermatitis (PTD)
- Skin fold pyoderma = intertrigo
- Bacterial overgrowth (ddx Malassezia dermatitis) common in dogs with cAD (atopic dermatitis)
What are hotspot/pyotraumatic dermatitis?
What breeds are predisposed?
- Lesions develop within hours due to self-trauma
- Underlying allergy (FAD) or pruritic/painful trigger
- Rottweiler, Golden Retriever & GSD predisposed
- Lesions usually on cheek, neck or rump
- Well-demarcated flat eroded moist lesion with erythematous halo
How does intertrigo form?
- Compromised barrier
- friction, altered micro-climate, loss of normal ventilation and/or accumulation of fluids
- Microbes proliferate, produce toxins & create inflammation
- May have concurrent skin disorder e.g., canine atopic dermatitis
– may progress to superficial or deep infection
Malassezia dermatitis is uncommon in cats - what are the predisposed breeds?
Devon rex
Sphinx
Persian
What dog breeds are predisposed to Malassezia dermatitis?
Basset hounds
West highland white terrier
Cocker spaniels
What is malassezia dermatitis a secondary disease in?
– Thymoma-induced exfoliative dermatitis
– Paraneoplastic alopecia
– FIV or FeLV
– Feline allergy
What are the clinical signs of malassezia dermatitis?
- Seborrhoeic dermatitis in Devon Rex and Sphynx
– paronychia with brown nails - Otitis
- Keratinisation disorders
– e.g., chin acne, idiopathic facial dermatitis of Persians
What condition is seen at the superficial depth?
*Superficial folliculitis
-usually staphylococci
