title: Does Preoperative Antimicrobial Prophylaxis Influence the Diagnostic Potential of Periprosthetic Tissues in Hip or Knee Infections?
abstract: BACKGROUND
  Undiagnosed low-grade prosthetic joint infections (PJI) are recognized as an important reason for early failure of presumably aseptic revisions. Preoperatively administered antimicrobial prophylaxis reduces the incidence of PJI but it may reduce the sensitivity of microbiologic periprosthetic tissue cultures and consequently increase the incidence of undiagnosed septic prosthetic joint failures, which can lead to catastrophic serial revisions.
  
  
  OBJECTIVE
  We wished to determine whether administration of preoperative antibiotics decreases the likelihood of diagnosing PJI in patients undergoing revision hip or knee arthroplasty in whom infection is suspected.
  
  
  METHODS
  We prospectively enrolled and evaluated 40 patients (29 with THAs and 11 with TKAs) who met the following inclusion criteria: older than 18 years, with suspected PJI of unknown cause, undergoing surgical revision. After arthrotomy, three tissue samples were obtained for microbiologic analysis and diagnosis, and antimicrobial prophylaxis (cefazolin 2 g intravenously) then was administered. Later during the procedure, but before débridement and irrigation, the second set of three tissue samples was obtained from the same surgical area and was cultured. Tissue concentration of prophylactic antibiotic was verified with the second set of samples. A positive culture result was defined as one or more positive cultures (growth on agar at or before 14 days). We then compared the yield on the microbiologic cultures obtained before administration of antibiotics with the yield on the cultures obtained after antibiotics were administered. An a priori analysis was performed; with the numbers available, we had 98% power to detect a difference in diagnostic sensitivity of 33%.
  
  
  RESULTS
  With the numbers available, we found no difference in the likelihood that an infection would be diagnosed between the samples obtained before and after administration of antimicrobial prophylaxis (odds ratio [OR] for positive microbial culture = 0.99; 95% CI, 0.40-2.48; p = 0.99). All measured tissue concentrations of cefazolin were greater than the minimum inhibitory concentration, therefore we found that antibiotic prophylaxis was adequate at the time of second-set tissue specimen recovery.
  
  
  CONCLUSIONS
  Results from this small, prospective series suggest that preoperative antimicrobial prophylaxis may be administered safely even in patients undergoing revision hip or knee arthroplasty in which microbiologic sampling is planned without compromising the diagnostic sensitivity of tissue sample cultures. However, before applying our results more generally, our findings need to be confirmed in larger, multicenter studies that would allow evaluation by sex, procedure, bacteriology, and other potentially important factors.
  
  
  METHODS
  Level I, diagnostic study.
authors.affiliation: Department of Orthopaedics, General Hospital Novo Mesto, Novo Mesto, Slovenia.
authors.forename: Klemen
authors.initials: K
authors.lastname: Bedenčič
authors.affiliation: Medical Microbiology Department, Institute of Public Health, Koper, Slovenia.
authors.forename: Martina
authors.initials: M
authors.lastname: Kavčič
authors.affiliation: Valdoltra Orthopaedic Hospital, Jadranska Cesta 31, 6280, Ankaran, Slovenia.
authors.forename: Nataša
authors.initials: N
authors.lastname: Faganeli
authors.affiliation: Valdoltra Orthopaedic Hospital, Jadranska Cesta 31, 6280, Ankaran, Slovenia.
authors.forename: Rene
authors.initials: R
authors.lastname: Mihalič
authors.affiliation: Orthopaedic Clinic University Clinical Centre, Ljubljana, Slovenia.
authors.forename: Blaž
authors.initials: B
authors.lastname: Mavčič
authors.affiliation: National Veterinary Institute, Ljubljana, Slovenia.
authors.forename: Jožica
authors.initials: J
authors.lastname: Dolenc
authors.affiliation: National Veterinary Institute, Ljubljana, Slovenia.
authors.forename: Zlatka
authors.initials: Z
authors.lastname: Bajc
authors.affiliation: Valdoltra Orthopaedic Hospital, Jadranska Cesta 31, 6280, Ankaran, Slovenia. rihard.trebse@ob-valdoltra.si.
authors.forename: Rihard
authors.initials: R
authors.lastname: Trebše
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D019072:Antibiotic Prophylaxis; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation; D003646:Debridement; D004334:Drug Administration Schedule; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016459:Prosthesis-Related Infections / Q000175:diagnosis* / Q000382:microbiology / Q000601:surgery; D012086:Reoperation; D012307:Risk Factors; D007507:Therapeutic Irrigation; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents