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Table 3 Association between surgical site infections and duration, timing, and antibiotic prophylaxis agent, adjusted for age, sex, ASA score, and duration of operation

From: Risk of surgical site infection and efficacy of antibiotic prophylaxis: a cohort study of appendectomy patients in Thailand

Predictor variable N Infection Rate* Relative risk
     Crude 95% CI Adjusted** 95% CI
Duration of antibiotic prophylaxis        
   None 167 5 3.0 1.00 Reference 1.00 Reference
   1 day 1159 12 1.0 0.34 0.12–0.97 0.30 0.10–0.88
   >1 day 813 9 1.1 0.36 0.12–1.09 0.32 0.10–0.98
Time of first antibiotic dose administration        
   None 167 5 3.0 1.00 Reference 1.00 Reference
   >1 hour preoperatively 1004 8 0.8 0.26 0.08–0.81 0.22 0.07–0.70
   ≤ 1 hour preoperatively or interoperation 814 9 1.1 0.36 0.12–1.09 0.33 0.11–1.02
   Postoperatively 154 4 2.6 0.86 0.23–3.28 0.78 0.20–3.00
Antibiotic agent        
   None 167 5 3.0 1.00 Reference 1.00 Reference
   Single dose combination metronidazole and gentamicin 766 8 1.0 0.34 0.11–1.06 0.28 0.09–0.90
   Combination metronidazole and gentamicin within 1 day 130 1 0.8 0.25 0.03–2.18 0.22 0.03–1.98
   Combination metronidazole and gentamicin > 1 day 370 4 1.1 0.35 0.09–1.34 0.29 0.08–1.12
   Others*** 706 8 1.1 0.37 0.12–1.15 0.37 0.12–1.15
  1. * Rate = infections/100 operations
  2. ** Adjusted for age, sex, ASA score, and duration of operation
  3. *** Others: Penicillin, amoxicillin, amoxicillin/clavulanate, ampicillin, cloxacillin, cefazolin, cephalexin, cefotaxime, ceftriaxone, ceftazidime, cefdinir, cefoxitin, ofloxacin, norfloxacin, cotrimoxazole, chloramphenical, fosfomycin, clindamycin, and amikacin.