This patient should undergo Gram stain and culture of the fluid drainage from the incision site. Most surgical site infections (SSIs) occur within 30 days of the surgical procedure, except in procedures involving an implant, which may present up to a year after the operation. SSIs are categorized as superficial incisional, deep incisional, and organ/deep space infections. They are differentiated on the basis of presenting clinical signs and symptoms as well as the implicated organism (for example, some organisms cause minimal to no drainage). A superficial incisional infection involves only the skin and subcutaneous tissues, whereas a deep incisional infection involves the underlying soft tissue. Signs and symptoms of a superficial incisional infection include inflammatory changes at the incision site, with or without purulent drainage, and generally without systemic signs of infection such as fever, as seen in this patient. In such situations, the infection is usually managed with antibiotics alone and does not require debridement. Although the organisms obtained from a drainage culture may only reflect skin flora, the culture and Gram stain are helpful for identifying possible antibiotic-resistant organisms not covered by empiric therapy. Deep incisional SSIs generally present with more systemic signs of infection (fever, leukocytosis), and management requires debridement and antibiotic therapy guided by results of deep tissue cultures.

A patient with a superficial incisional SSI would not be expected to be bacteremic, so a blood culture would not be helpful in guiding management. Obtaining blood cultures should be guided by the clinical presentation and may be useful in some patients with organ/deep space SSIs.

Surgical site imaging with ultrasonography or CT may be helpful in patients with suspected organ/deep space SSIs to localize the site of infection, identify any fluid collections, and help to plan a drainage procedure. However, imaging would not be helpful in this patient who has a superficial SSI.