Pyoderma is a common bacterial skin disease, most often a canine problem. Staphylococcus intermedius is the most common bacterial culprit involved in pyo-derma. Staphylococcus intermedius is part of the normal skin flora and colonizes the upper respiratory tract, the oral cavity, the anal region, and the external ear canal. Most canine staphylococci produce slime, which allows the bacteria to adhere to cells, and contain protein A, which activates the complement cascade and incites inflammation. Escherichia coli, Proteus spp., and Pseudomonas spp. can transiently colonize the skin and may occasionally become involvedin pyoderma, sec-ondary to a staphylococcal infection. Actinomycetes spp., Actinobacillus spp., mycobacteria, and various fungi can also be involved in skin diseases.