This patient is presenting with signs and symptoms of peritonitis, a known complication of Continuous Ambulatory Peritoneal Dialysis (CAPD). In CAPD-related peritonitis, the most common causative organism is coagulase-negative staphylococci, which includes Staphylococcus epidermidis. These organisms are part of the normal skin flora and can be introduced into the peritoneal cavity during the process of connecting or disconnecting dialysis bags.