DR: canine pyoderma Flashcards
3 types of pyoderma
surface, superficial and deep
Describe surface and superficial pyodermas
epidermis only, don’t penetrate below BM. typically exudative. lesions include papules, pustules, epidermal collarettes, scales, crusts, often pruritus.
Describe deep pyoderma
penetrate below BM into dermis and depper tissues, lesions include haemorrhagic bullae, nodules, ulcers, draining tracts (haemorrhagic or purulent discharge)
How is pyoderma diagnosed? 5 types?
problem-based classification based on lesion appearance:
- SEBORRHOEIC PYODERMA - erythema, erosions, exudation without pustules and collarettes
- PAPULES, PUSTULES, SCALE, FOCAL ALOPECIA
- EROSIONS and/or ULCERS
- ULCERS AND DRAINING SINUS TRACTS
- NODULES and/or REGIONAL SWELLING
Name 2 causes of seborrhoeic pyodermas - erythema, erosion, exudation without pustules and collarettes
- bacterial overgrowth syndrome
- intertrigo
Name 3 causes of PAPULES, PUSTULES, SCALE and FOCAL ALOPECIA
- impetigo (epidermal pustules not centered on hair follicle)
- bacterial folliculitis (commonest cause of canine pyoderma)
- superficial seasonal pyoderma
Name 3 causes of EROSIONS and/or ulcers
- pyotraumatic dermatitis
- intertrigo (severe cases)
- mucocutaneous pyoderma (GSDs)
What causes the ULCERS and DRAINING SINUS TRACT form of pyoderma?
- Furunculosis (deep pyoderma) = associated with rupture of hair follicles, contents spill into dermis, creates FB reaction in dermis or subcutis. Localised or widespread
What is feline chin acne?
a type of furunculosis (i.e. depp pyoderma) with ULCERS and DRAINING SINUS TRACTS. it is a keratinisation disorder associated with comedones and furuncle formation.
What may cause the NODULE and/or REGIONAL SWELLING form of canine pyoderma?
- abscess
- cellulitis (diffuse infection and inflammation along tissue planes)
What is necrostising fasciitis?
a rare but severe form of cellulitis associated with dissemination of bacterial toxins
How is pyoderma diagnosed?
- CS highly suggestive
- confirmed with cytology
- and where necessary bacterial culture and AB sensitivity
What are the 4 main cytological techniques for diagnosing canine pyoderma?
- adhesive tape strip cytology
- direct impression smears
- indirect impression smears
- needle cores and FNAs
What is adhesive tape strip cytology good for?
- removes outer SC layer and adherent microorganisms
- sample dry, greasy, scaling or eroded lesions
- irregular surfaces or restricted sites
When are impression smears useful?
- moist or seborrhoiec lesions
- direct - erosion, crust underside or ruptured pustule
- indirect - when slide cannot be apposed to skin and adhesive tape strips are unsuitable (use cotton bud etc)
When are needle cores useful?
- cutaneous massess and enlarged LNs
How are cytology samples stained?
- Diff-Quik (inflammatory cells and microorganisms
- heat fixation not necessary
- Gram and Ziehl-Nielsen (more precisely ID bacteria_
Describe inflammatory cells in canine pyoderma
- neutrophils predominate in most cases
- degenerate/toxic indicate infection
- non-degenerate (sterile inflammation)
- both may be seen
- macrophages + microorganisms, degnerate cells, other debris suggest chronic and/or deep pyoderma
- many macrophages or MNGCs - mycobacterial or fungal infection
- most inflammatory reactions have moderate lymphocytes, PCs and eosinophils - little diagnostic significance
What is bacterial overgrowth like on cytology?
large numbers of bacteria, often several different forms, with no or only minimal numbers of inflammatory cells
Is the presence of intracytoplasmic bacteria a definite indicator of infection?
yes