Final answer:
The most common cause of peritonitis is bacterial infections, particularly those caused by Gram-negative bacteria, with Escherichia coli being the most frequent pathogen.
Step-by-step explanation:
In the context of peritonitis, the most common cause of this severe inflammation of the peritoneum is bacterial infections. Specifically, Gram-negative bacteria are frequently implicated as the primary pathogens in peritonitis. Examples of Gram-negative bacteria that can cause peritonitis include Escherichia coli (most commonly), Proteus vulgaris, Pseudomonas aeruginosa, and Klebsiella pneumoniae. These bacteria may enter the peritoneal cavity through a breach in the wall of the alimentary canal, such as from conditions like appendicitis, colonic diverticulitis, or pelvic inflammatory disease. Intensive antibiotic therapy alongside potential emergency surgery is often required to manage peritonitis and reduce its historically high mortality rates.