Standardized incidence rates of surgical site infection: a multicenter study in Thailand.

Background: No previous multicenter data regarding the incidence of surgical site infection (SSI) are available in Thailand. The magnitude of the problem resulting from SSI at the national level could not be assessed. The purpose of this study was to estimate the incidence of SSI in 9 hospitals, together with patterns of surgical antibiotic prophylaxis, risk factors for SSI, and common causative pathogens.

Methods: A prospective data collection among patients undergoing surgery in 9 hospitals in Thailand was conducted. The National Nosocomial Infection Surveillance (NNIS) system criteria and method were used for identifying and diagnosing SSI. The SSI rates were benchmarked with the NNIS report by means of indirect standardization and reported in terms of standardized infection ratio (SIR). Antibiotic prophylaxis was categorized into preoperative, intraoperative, and postoperative. Risk factors for SSI were evaluated using multiple logistic regression models.

Results: From July 1, 2003, to February 29, 2004, the study included 8764 patients with 8854 major operations and identified 127 SSIs, yielding an SSI rate of 1.4 infections/100 operations and a corresponding SIR of 0.6 (95% CI: 0.5-0.8). Of these, 35 SSIs (27.6%) were detected postdischarge. The 3 most common operative procedures were cesarean section, appendectomy, and hysterectomy. The 3 most common pathogens isolated were Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, which accounted for 15.3%, 8.5%, and 6.8% of infections, respectively. The 3 most common antibiotics used for prophylaxis were ampicillin/amoxicillin, cefazolin, and gentamicin. The proportion of types of antibiotic prophylaxis administered were 51.6% preoperative, 24.3% intraoperative, and 24.1% postoperative. Factors significantly associated with SSI were high degree of wound contamination, prolonged preoperative hospital stay, emergency operation, and prolonged duration of operation.

Conclusion: Overall SSI rates were less than the average NNIS rates. The causative pathogens of SSI were different from those of other reports. There was a crucial proportion of operations that did not comply with the antibiotic guidelines. The risk factors for SSI identified in this study were consistent with most other reports.