Chapter 100

Staphylococcus species are both normal resident cutaneous microflora and opportunistic pathogens frequently associated with pyoderma in dogs and cats. Staphylococcus species usually are divided into coagulase-positive and coagulase-negative species, with the former most often associated with skin infections. Recently, Staphylococcus intermedius has been reclassified, with Staphylococcus pseudintermedius being recognized as the common coagulase-positive canine staphylococcus (Sasaki et al, 2007). Staphylococcus aureus, Staphylococcus schleiferi, and coagulase-negative staphylococci occasionally are isolated from skin infections of animals. Often these isolates are methicillin- and multidrug resistant, which most likely is attributable to empiric treatment with multiple classes of antibiotics before culture (see Chapter 103). Methicillin resistance implies resistance to all β-lactam antibiotics including cephalosporins and amoxicillin/clavulanic acid. S. aureus, S. schleiferi, and coagulase-negative staphylococci, unlike S. pseudintermedius, also are human pathogens or opportunistic invaders. Identification of the causative organism is important to determine the likelihood of resistance as well as the source and possible human risk.