In some cases, antibiotics are the only treatment necessary for peritonitis and its associated conditions (e.g., bacteremia, sepsis). This is especially true in cases of primary bacterial peritonitis (PBP). For example, PBP that is treated with antibiotics often improves within 72 hours, with therapy lasting anywhere from a couple of days to two weeks.

Secondary peritonitis may also be treated with antibiotics. However, surgery is usually necessary to treat the source of the inflammation and infection in secondary peritonitis, which can be life-threatening. This may include removing an inflamed appendix, infected bowel or abscess. Antibiotics will also be administered promptly. Patients who undergo surgery may receive intravenous (I.V.) fluids and electrolytes, and a tube may be inserted through the nose and into the stomach or intestine to drain excess fluid or gas.

Continuous ambulatory peritoneal dialysis (CAPD) peritonitis is also treated with antibiotics.