Zoonotic Streptococcus canis Bacteremia Following a Dog Scratch in an Elderly Patient With a Nonconditional Pacemaker

Streptococcus canis is a β-hemolytic Group G streptococcus commonly found in the microbiome of dogs and cats and is an uncommon cause of invasive human infection. Although typically regarded as a veterinary pathogen, S. canis has been reported to cause bacteremia, endocarditis, and other severe infections in humans, particularly in older adults with significant comorbidities or implanted medical devices. We describe a case of Streptococcus canis bacteremia in an 89-year-old woman with multiple comorbidities and a nonconditional permanent pacemaker who presented with fever, dyspnea, and severe lower back pain. Blood cultures grew S. canis, identified using standard microbiologic techniques. The clinical course raised concern for metastatic infection and pacemaker involvement. Imaging of the thoracic and lumbar spine demonstrated no evidence of discitis or osteomyelitis, and both transthoracic and transesophageal echocardiography showed no valvular or pacemaker lead vegetations. Further history revealed a dog scratch several weeks prior to presentation that resulted in skin disruption, representing a plausible portal of entry. The patient was treated with intravenous ceftriaxone with rapid clinical improvement, resolution of hypoxia, clearance of bacteremia, and declining inflammatory markers. She was discharged to inpatient rehabilitation to complete a 2-week course of antimicrobial therapy and recovered without evidence of recurrent infection. This case underscores Streptococcus canis as an uncommon but clinically relevant zoonotic pathogen and highlights the importance of detailed exposure history, appropriate microbiologic identification, and careful evaluation for device-related infection in high-risk patients.