Sepsis Caused by Streptococcus canis: An Underrecognized Zoonotic Infection in an Elderly Dog Owner

Streptococcus canis ( S. canis ) is an underrecognized zoonotic pathogen capable of causing invasive human infection. We report a case of sepsis with acute hypoxic respiratory failure due to S. canis bacteremia in a 73-year-old woman with multiple comorbidities, including breast cancer complicated by chronic lymphedema and cardiovascular disease. She presented with fever, progressive dyspnea, hypoxemia, leukocytosis, acute kidney injury, and rising cardiac troponin levels. Imaging demonstrated bilateral interstitial opacities consistent with pulmonary edema, and her clinical course required intensive care management. Two sets of blood cultures grew S. canis , a group G β-hemolytic streptococcus most commonly associated with dogs and cats. Species-level identification was achieved using polymerase chain reaction–based blood culture testing followed by automated biochemical confirmation. The patient was initially treated with broad-spectrum antibiotics and subsequently transitioned to intravenous penicillin G after susceptibility testing demonstrated β-lactam sensitivity. Further history revealed frequent exposure to a household dog without history of bites or scratches, supporting probable non-traumatic zoonotic transmission. The patient improved with targeted therapy and completed a 13-day course of intravenous antibiotics. This case demonstrates that S. canis can cause severe cardiopulmonary compromise in elderly patients and highlights the epidemiologic value of species-level identification in recognizing zoonotic transmission and prompting targeted assessment of animal exposure in patients with group G streptococcal sepsis. • Streptococcus canis is an underrecognized zoonotic cause of sepsis. • Sepsis occurred without history of animal bites or trauma. • Infection presented with cardiopulmonary complications in an elderly host. • Species-level identification clarified zoonotic transmission risk. • Animal exposure history should be routine in group G streptococcal infections.