CHAPTER 13 BACTERIAL PYODERMA 213
Predisposing Factors
Systemic immuno-incompetence (metabolic disease, genetically determined cellular
immunodeficiency).
Trauma/damage to the skin (e.g., pressure, licking, scratching, parasites).
Follicular damage (e.g.,Demodexmites, dermatophytes).
Dermal damage (e.g., collagen disruption, extension of disease, foreign body reac-
tion).
Physical factors (e.g., poor grooming, maceration of the skin, heat, humidity).
Inappropriate antibacterial therapy: too short a course, poor drug choice, inappropri-
ate dose.
Three Categories of Bacterial Infections
Surface (overgrowth or colonization of the epidermis by bacteria):
Intertrigo (skinfold “pyoderma”)
Acute moist dermatitis (“hot spot”).
Superficial pyoderma (infection confined within the epidermis and follicles):
Impetigo (puppy pyoderma): nonfollicular subcorneal pustules
Mucocutaneous pyoderma
Canine exfoliative superficial pyoderma
“Superficial spreading pyoderma” (large coalescing epidermal collarettes due to
interfollicular pustules)
Superficial bacterial folliculitis (superficial portion of the hair follicle)
Miliary dermatitis in cats.Deep pyoderma (ruptured hair follicle and extension of infection into the dermis and
SQ):
Muzzle folliculitis and furunculosis (chin acne)
Nasal pyoderma (rapid onset, bridge of nose)
Pedal pyoderma and interdigital furunculosis/nodules
Generalized deep pyoderma/cellulitis (German shepherd dog, familial)
Bacterial granulomas (“acral lick dermatitis/furunculosis”)
Pressure point pyoderma
Pyotraumatic folliculitis and furunculosis.Common Bacterial Infections
Staphylococcus pseudintermedius: most frequent canine; also recognize other spp. of
staph. causing pyoderma –S. schleiferiandS. aureus(methicillin resistance among
staphylococcal species is an emerging clinical problem in canine patients).Pasteurella multocida: an important pathogen in cats.
Deep pyoderma (furunculosis) may be complicated by gram-negative organisms (e.g.,
E. coli,Proteusspp.,Pseudomonasspp.); emerging resistance has been noted in these
organisms.Rarely caused by higher bacteria (e.g.,Actinomyces,Nocardia, mycobacteria,Acti-
nobacillus).