Which of the following is a common post-surgical infection?

When considering common post-surgical infections, it's important to recognize that they typically arise at the site of the surgical procedure or can develop as a systemic response to surgery. Gastrointestinal infections can indeed occur post-surgery, particularly if the surgery involves the abdominal area or if the patient has a history of gastrointestinal issues. These infections can be a result of several factors, including contamination during the surgical procedure, the disruption of normal gut flora, or an impaired immune response following surgery.

In contrast, while pneumonia is a known complication in post-surgical patients, especially those undergoing surgeries that affect lung function or mobility, it is not classified as a common infection. Skin rashes may occur for a variety of reasons but are usually not considered infections unless they have an infectious etiology, which is not common. Diabetes, while a significant medical condition that can complicate recovery, is not an infection and therefore does not fit the context of the question regarding infections. Thus, gastrointestinal infections are recognized as potential complications following surgical procedures, making them a fitting answer in the context of common post-surgical infections.