Organisms causing SSI: Staphylococcus aureus is the main organism causing Surgical Site Infections (SSI), although other organisms like clostridia and gram-negative bacteria can also cause SSI. Colonization refers to the presence of bacteria in a wound without any symptoms or signs of systemic inflammation, while contamination is the transient exposure of a wound to bacteria for usually less than 6 hours. Protective mechanisms against infections, such as mechanical barriers (skin), chemical barriers (low gastric pH), humoral defenses (antibodies, complement, opsonins), and cellular defenses (phagocytic cells, macrophages, PMNL, killer lymphocytes, etc.), can be compromised by surgical interventions and treatments. Risk factors for an increased risk of wound infections include metabolic diseases like diabetes, uremia, and jaundice, malnutrition (including obesity and weight loss), immunosuppression due to conditions like cancer, AIDS, the use of steroids, chemotherapy, and radiotherapy, as well as colonization and translocation of bacteria in the gastrointestinal tract.