A sterile site culture is a culture obtained from a normally sterile site such as blood, synovial or pleural fluid or sterile aspirates. Confusion sometimes arises in determining whether a swab or aspirate is sterile or superficial (that is, not from a sterile site). Generally the only swabs which are from sterile sites are those which are taken in the operating room during surgery - if this is not the case, it is safe to assume that the isolate is from a non-sterile site. Aspirates are usually from sterile sites, and such cases are included in the surveillance definition. An aspirate culture can be obtained through needle aspiration or during a percutaneous drainage procedure.