a patient with peritonitis can spread infection to others during handling with peritoneal dialysis equipment, or during taking samples of his/her peritoneal fluid. Nurses or doctors themselves could attract skin or gastrointestinal infections this way; they could also spread infection to other patients, eventually resulting in peritonitis, usually via abdominal catheters.

Indirectly, you can “catch” peritonitis by attracting sexually transmitted disease, like gonorrhea, from a patient, who developed peritonitis from gonnorhea.