What is the most common bacteria found in post-surgical abdominal infections?

The most common bacteria found in post-surgical abdominal infections is Bacteroides fragilis. This anaerobic bacterium is a significant member of the normal flora of the human intestines and is particularly associated with intra-abdominal infections. When surgical intervention occurs, it is possible for the protective barriers of the gut to be breached, allowing Bacteroides fragilis to enter the sterile environment of the abdominal cavity.

Bacteroides fragilis is known for its ability to proliferate in low-oxygen environments, which makes it well-suited to thriving in the conditions present during and after abdominal surgeries. The bacterium can cause abscess formation and peritonitis, leading to significant morbidity if not appropriately identified and treated.

While other bacteria listed, such as Staphylococcus aureus and Escherichia coli, can also contribute to post-surgical infections, they are less frequently implicated in the specific context of abdominal infections compared to Bacteroides fragilis. Pseudomonas aeruginosa is more typically associated with infections in immunocompromised individuals or external environmental sources rather than being a common flora in abdominal contexts.