Which of the following bacteria is the most common cause of surgical site infection?

Staphylococcus aureus is the most common cause of surgical site infections (SSIs) largely due to its prevalence in the skin flora of humans. This bacterium can easily contaminate surgical wounds, especially in cases where the skin is breached during procedures. It is a robust pathogen, capable of forming biofilms and producing various virulence factors that promote infection and tissue damage.

The likelihood of Staphylococcus aureus causing infections is further heightened by its ability to be transmitted from healthcare workers or the environment to patients undergoing surgical procedures. As a result, it is often the primary organism isolated in SSIs, leading to significant morbidity and extended hospital stays.

The other bacteria listed—Streptococcus pneumoniae, Clostridium perfringens, and Escherichia coli—are associated with infections but are not the most common causes of SSIs. Streptococcus pneumoniae is primarily known for respiratory infections, Clostridium perfringens is often involved in gas gangrene, and Escherichia coli is more commonly linked to urinary tract infections and intra-abdominal infections rather than surgical site infections.