Selection of Prophylactic Antimicrobial Agent May Affect Incidence of Infection in Small Bowel and Colorectal Surgery

Background: Antibiotic prophylaxis guidelines suggest single-dose regimens are adequate, but comparisons of multiple agents are lacking. We compared post-operative infection rates retrospectively among six common prophylactic agents given as a single dose to colorectal surgery patients. Methods: A commercial database supplied demographics, All-Patient Refined Diagnosis-Related Groups (APR DRGs), International Classification of Disease (ICD)-9 codes, and drug utilization information for patients discharged from 303 hospitals from January 2007-December 2008 whose charts had been sampled for reporting Surgical Care Improvement Project (SCIP) measures. The patients (n = 4,634) had the same APR DRG, no baseline infection, and prophylaxis discontinued within 24 h of surgery. Development of infection was determined by ICD-9 code. "Single dose" was defined as <= 3 g of ampicillin-sulbactam (AMP); <= 2 g of cefotetan (CFT), cefoxitin (FOX), or ertapenem (ERT); or metronidazole and <= 2 g of cefazolin (CFZ) or <= 750mg of levofloxacin (LVX) given on the day of the procedure. Multivariable logistic regression evaluated factors associated with infection, including agent choice. Results: Frequency of use and rate of infection (3.7% overall) were FOX 1,752 (4.9%), ERT 1,166 (2.7%), CFZ 549 (2.7%), AMP 447 (3.6%), LVX 402 (3.2%), and CFT 318 (3.5%). The unadjusted infection rate differed by agent (p = 0.037). Multiple regression analysis found infection to be associated significantly with increasing APR DRG severity, longer procedures, younger age, and male gender (p < 0.01 for each except p = 0.02 for age), as well as agent choice. Among agents (vs. FOX as reference), ERT was associated with a lower infection rate (odds ratio 0.53; 95% confidence interval 0.34-0.82; p < 0.01); the odds ratio for all other agents contained the value 1.0. Conclusions: Agent selection among prophylactic antibiotics is one of many factors associated with infection development in colorectal surgery patients.