Capnocytophaga canimorsus, oral inhabitants of dogs and cats is a cause of zoonotic infections. It is transmitted to humans by bites, scratches, licks, or close exposure to these animals. Infections due to Capnocytophaga canimorsus have a wide range of severity and can sometimes be fatal. We report the case of an 89-years-old man who suffered from a sudden swollen native right shoulder. The blood test revealed an inflammatory syndrome and cytologic evaluation of joint aspiration showed an elevated nucleated cells count suspicious of infection. A Gram-negative bacillus grew after 48 h in the arthrocentesis and was identified as Capnocytophaga canimorsus. After 4 days, blood culture also grew Capnocytophaga canimorsus leading to the diagnosis of hematogenous septic arthritis of a non-prosthetic right shoulder. Antimicrobial therapy was empirically started with cefuroxime then switched to doxycycline for seven weeks with good clinical outcomes. It is important to inquire about patients’ environment including their proximity to animals as it can lead to zoonotic infections that can be of high severity. Moreover, hygiene rules must be applied when dog scratches or lick wounds occurred to avoid the spread of zoonotic germs. Prophylactic antibiotic therapy should be given for animal bites.
