Streptococcus canis is a commensal bacteria found on dogs' skin and mucosa of the respiratory, urogenital, and digestive tracts. S. canis is also on occasion an opportunistic pathogen, and it has been implicated in a variety of infections including otitis externa, mastitis, pharyngitis, tonsilitis, and in infections of wounds and the lower urinary tract (Greene and Prescott, 1998). Recently, however, two new forms of S. canis infections in dogs have been recognized; streptococcal toxic-shock syndrome (STSS) and necrotizing faciitis (NF). These infections are remarkable for their acute onset, severity, and clinical resemblance to human STSS and NF, although S. Pyogenes is the cause of these infections in humans. Canine NF responds well to prompt treatment with beta-lactam antibiotics. STSS in dogs, however, has a high mortality rate.