Isolated bacteria and drug susceptibility associated with the course of surgical site infections.

Bacterial culture is not often performed for mild surgical site infections, so only isolates from patients with severe surgical site infections have been identified. Consequently, broad-spectrum antibacterials, such as carbapenems, whose resistance has been highly modified, have been selected for use from the initial stage of these infections, and this is one reason for the increase in drug-resistant bacteria. We carried out this study to show antibiotics that are appropriate for each period of such infections. Bacteria obtained from postoperative infection sites in 114 patients with surgical site infections after gastrointestinal surgery were classified as first, second, third, and fourth isolates: the first isolates were taken when the administration of prophylactic antibiotics was finished, and the second, third, and fourth isolates were taken when the administrations of the first, second, and third therapeutic antibiotics, respectively, were finished. The incidence of drug-resistant strains was rare in strains isolated in the early phase of infections. The numbers of strains resistant to cephems and carbapenems increased as the clinical course of the infection progressed. New broad-spectrum antibiotics such as carbapenems should not be selected for the treatment of early-phase surgical site infections.