title: Prolonged antibiotic prophylaxis after cardiovascular surgery and its effect on surgical site infections and antimicrobial resistance.
abstract: BACKGROUND
  Despite evidence supporting short antibiotic prophylaxis (ABP), it is still common practice to continue ABP for more than 48 hours after coronary artery bypass graft (CABG) surgery.
  
  
  RESULTS
  To compare the effect of short (<48 hours) versus prolonged (>48 hours) ABP on surgical site infections (SSIs) and acquired antimicrobial resistance, we conducted an observational 4-year cohort study at a tertiary-care center. An experienced infection control nurse performed prospective surveillance of 2641 patients undergoing CABG surgery. The main exposure was the duration of ABP, and main outcomes were the adjusted rate of SSI and the isolation of cephalosporin-resistant enterobacteriaceae and vancomycin-resistant enterococci (acquired antibiotic resistance). Adjustment for confounding was performed by multivariable modeling. A total of 231 SSIs (8.7%) occurred after a median of 16 days, including 93 chest-wound infections (3.5%) and 13 deep-organ-space infections (0. 5%). After 1502 procedures using short ABP, 131 SSIs were recorded, compared with 100 SSIs after 1139 operations with prolonged ABP (crude OR, 1.0; CI, 0.8 to 1.3). After adjustment for possible confounding, prolonged ABP was not associated with a decreased risk of SSI (adjusted OR, 1.2; CI, 0.8 to 1.6) and was correlated with an increased risk of acquired antibiotic resistance (adjusted OR, 1.6; CI, 1.1 to 2.6).
  
  
  CONCLUSIONS
  Our findings confirm that continuing ABP beyond 48 hours after CABG surgery is still widespread; however, this practice is ineffective in reducing SSI, increases antimicrobial resistance, and should therefore be avoided.
authors.affiliation: Department of Epidemiology , Harvard School of Public Health, and Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. harbarth@a1.tch.harvard.edu
authors.forename: S
authors.initials: S
authors.lastname: Harbarth
authors.forename: M H
authors.initials: MH
authors.lastname: Samore
authors.forename: D
authors.initials: D
authors.lastname: Lichtenberg
authors.forename: Y
authors.initials: Y
authors.lastname: Carmeli
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D019072:Antibiotic Prophylaxis; D013504:Cardiovascular Surgical Procedures; D015331:Cohort Studies; D004352:Drug Resistance, Microbial; D005260:Female; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care; D012307:Risk Factors; D013530:Surgical Wound Infection / Q000453:epidemiology / Q000382:microbiology* / Q000517:prevention & control*; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents