Careful consideration should be made as to the antibiotic used in dogs with severe soft tissue infections with subcutaneous cellulitis, pyrexia, +/- signs of severe sepsis or septic shock. Some dogs have a history of injury but others may not. Approximately 60% of these dogs have strep or staph as the causative agent. Strep in particular is good at causing septic shock. Fluroquinolones are contraindicated in severe soft tissue/necrotizing infections because they have limited activity against strep and they can cause bacteriophage induced lysis of S. Canis which enhances its pathogenicity.
Antibiotic recommendations include:
Good coverage would be clindamycin and ceftriaxone, ampicillin and amikacin/gentamicin, or ampicillin/ceftriaxone. Ultimately the choice may change depending on what other underlying diseases are present.