CHAPTER 13 BACTERIAL PYODERMA 215
Postgrooming furunculosis (most often caused byPseudomonas aeruginosa): unique
presentation of deep pyoderma initiated by bathing and/or grooming; acute and
extremely painful; patients often febrile. Combing, clipping, or overly aggressive
bathing against the direction of growth of the hair may cause traumatic rupture of
the hair follicle, inciting a foreign body reaction; dorsal midline is often the most
severely affected region; lesions often occur within 24–48 hours after grooming.
Short-coated breeds predisposed. Bacterial contamination of shampoos or equipment
may be important in the etiology of this condition (Figure 13.11).Bacterial overgrowth syndrome (BOG): due to overgrowth ofStaphylococcusspecies
on the surface of the skin. Bacterial toxins may act as superantigens triggering non-
specific inflammatory reactions. “Quorum sensing” may be a factor in this syndrome;
quorum sensing occurs when a certain density level of bacteria is exceeded, causing
expression of characteristics that switch bacterial metabolism from cell proliferation
to toxin production. Primary clinical signs are pruritus, erythema, and lichenification
in the absence of primary lesions such as papules and pustules. Often also associated
withMalasseziaovergrowth as well as underlying diseases such as atopic disease or
chronic glucocorticoid therapy. Topical shampoo therapy is required for therapeutic
success (Figure 13.12).Lesions
Papules
Pustules
Hemorrhagic bullae
Serous crusts (miliary dermatitis in the cat)
Epidermal collarettes: footprints of ruptured pustules with slow expansion in a cir-
cular pattern – both follicular and interfollicular (Figure 13.13)
Circular erythematous or hyperpigmented macules (Figure 13.14)
Target lesions
Multifocal alopecia leading to appearance of a “moth-eaten” hair coat
Scaling, follicular casts
Lichenification
Abscesses
Furunculosis, cellulitis
Draining tracts
Greasy skin
Malodor
DIFFERENTIAL DIAGNOSIS
Atopic dermatitis
Parasitic dermatitis (fleas, scabies, demodicosis, cheyletiellosis, etc.)
Cutaneous adverse food reaction
Neoplasia (e.g., cutaneous lymphoma)