Skin Infections 1 Flashcards
Infections of epidermis
Surface/superficial pyoderma
Infections of dermis
Deep pyoderma
Furunculosis
Cellulitis
Infections of fat
Paniculitis
Defense of skin
- Physical parameters
- Hair and dense stratum corneum
- Sloughing of skeratinized cells (desquamation)
- Secretions and excretions of skin
- Skin immune system
- Resident micro flora
Physical parameters defense
- Dryness - Conditions that interfere with evaporation
(^moisture) cause proliferation of resident and transient
bacteria - pH Although variable is usually acidic pH. If pH is <6.0 growth is “discouraged”
- temperature < 37ºC
Sloughing of keratinized cells
Intracellular cohesions is relaxed prior to sloughing
Gets rid of transient bacteria
Resident quickly repopulate
Secretions and excretions of skin
- Holocrine sebaceous glands secrete long chain FAs
(toxic lipids) which inhibit bacterial growth - Holocrine and apocrine sweat glands contribute to
intercellular seal in superficial epidermal layers, limiting microbial access - Sweat glands secrete lactate, proprionate, acetate, caprylate and high concentrations of NaCl
- Also interferon, lysoszyme, transferrin and Ig’s action of skin
1-2 present in all secretions
3-4 contribute to self sterilizing action
Skin immune system
Responds to local antigenic stimuli
Cells and their functions correspond to those in the other mucosal surfaces (e.g., GALT)
Prominent cell = Langerhans cells (dendritic cells)
antigen-presenting (take up and present
antigen to lymphocytes)
also release cytokines and chemokines that help promote inflammation. these cells are long term residents
Resident microflora
Limited to:
1. Surface of epidermal layers (stratum corneum)
Distal parts of ducts of sweat glands and hair follicles
2. Numbers highest in moist, protected areas
Axilla, inguinal, interdigital spaces and skin folds
But lower numbers than mucus membranes (10 2 – 105 cm2)
3. Exclude intruders by excreting inhibitory metabolites
(VFAs, antibiotics), bacteriocins
4. Prevent other bacteria from attaching (occupy available niches = colonization resistance)
Normal resident flora
Gram positive predominate
-Coagulase neg. Staphylococcus spp.*
-Micrococcus spp.
-a-haemolytic streptococci
-Proprionibacterium acnes
-Corynebacterium spp.
Gram negative - few
-Acinetobacter spp.
Lipophilic yeasts in low no’s
- Malassezia pachydermatis
Transient normal flora
Gram positive
-S. pseudintermedius (dogs)*
-S. aureus* (other species)
-β-hemolytic streptococci
-Enterococcus spp.
Gram negative
-E. coli*
-Proteus spp.
-Pseudomonas aeruginosa*
-Fecal bacteria – feet (farm)
Predisposing factors that encourage skin infections
Immune deficiency
Short fur
Skin folds/obesity
Trauma/exfoliation
Pyoderma
Pus in the skin
90% of cases of canine pyoderma caused by S Pseudointermedius
Deep pyoderma can involve others
Pyoderma is considered a 2* skin disease
Classifications of pyoderma
Surface pyoderma
Superficial pyoderma
Deep pyoderma
Surface pyoderma
Pyotraumatic dermatitis (“hotspots”) Ø
Skin fold pyoderma (intertrigo)
Mucocutaneous Pyoderma
