Snapshot A 29-year-old man presents to the emergency department 1 day after being in a fist fight at a bar. He punched his opponent in the mouth after having an argument, which resulted in a laceration of his dorsal hand. When he went home, he attempted to wash the laceration with soap and water and applied antibiotic cream. One day later, he developed swelling of the hand and pus was draining. Physical examination is notable for marked swelling in the ulnar aspect of the hand and severe tenderness over the fourth metacarpal joint, and pus is noted to be draining from the joint. Sensory examination is normal, and strength examination is limited by pain. In the emergency department, he obtained a radiograph of the hand, which did not demonstrate any acute fractures or foreign bodies. He immediately received a tetanus booster, and orthopedics was consulted for possible irrigation and drainage of the joint. Given the clinical extent of the infection, he is started on intravenous ampicillin-sulbactam. Introduction Definition bites caused by an animal or human human bites can also result from a fist hitting the person's mouth Microbiology general principle oral flora of the biting animal (e.g., dog and human) and skin animal bites Pasteurella, Staphylococcus and Streptococcus species, and anaerobic bacteria Bartonella henslae (leading to cat-scratch disease) human bites Eikenella corrodens aerobic gram-positive cocci (e.g., group A Streptococcus) anaerobes Epidemiology incidence dog bites are the most common cause of an animal bite cat bites are the second most common cause of an animal bite human bites (e.g., an actual human bite or a clenched fist injury to a human's mouth) are considered the third leading cause of bites ETIOLOGY Pathogenesis Dog bites crushing-type wound that can damage skin and deeper structures (e.g., muscle, tendon, bone, nerves, and vessels) Human bites clenched-fist injuries are most common login to view 2 more bullets Presentation Symptoms/physical exam dog bites range from login to view 2 more bullets cat bites typically affecting the upper extremities and face (especially cat scratches) human clenched-fist injury skin breaks over the knuckles general fever erythema and swelling tenderness purulent drainage lymphangitis Imaging Radiography of the involved body part (e.g., hand) indication in wounds near joints to evaluate for fractures and foreign bodies (e.g., embedded teeth) Studies Wound and blood cultures (aerobic and anaerobic) indication prior to antibiotic treatment in patients with an infected wound and signs of systemic infection Treatment Conservative wound cleaning (e.g., wound irrigation and debridement of devitalized tissue) indication login to view 1 more bullet Medical empiric antibiotic treatment indication login to view 9 more bullets medications login to view 4 more bullets tetanus prophylaxis indication login to view 8 more bullets comment login to view 3 more bullets rabies prophylaxis indication login to view 1 more bullet comments login to view 1 more bullet Operative primary closure indication login to view 1 more bullet comments login to view 1 more bullet delayed primary closure indication login to view 6 more bullets Complications Septic arthritis Osteomyelitis Deep soft tissue infection Prognosis Excellent in patients who promptly seek medical attention