title: Impregnation of bone chips with antibiotics and storage of antibiotics at different temperatures: an in vitro study.
abstract: BACKGROUND
  Allograft bone used in joint replacement surgery can additionally serve as a carrier for antibiotics and serve as a prophylaxis against infections. However, in vitro dose-response curves for bone chips impregnated with different kinds of antibiotics are not available. In addition, while it would be desirable to add the antibiotics to allograft bone chips before these are stored in a bone bank, the effects of different storage temperatures on antibiotics are unknown.
  
  
  METHODS
  Five different antibiotics (cefazolin, clindamycin, linezolid, oxacillin, vancomycin) were stored, both as pills and as solutions, at -80 degrees C, -20 degrees C, 4 degrees C, 20 degrees C and 37 degrees C; in addition, bone chips impregnated with cefazolin and vancomycin were stored at -80 degrees C and -20 degrees C. After 1 month, 6 months and 1 year, the activity of the antibiotics against Staphylococcus epidermidis was measured using an inoculated agar. The diameter of the S. epidermidis-free zone was taken as a measure of antibiotic activity. In a separate experiment, in vitro dose-response curves were established for bone chips impregnated with cefazolin and vancomycin solutions at five different concentrations. Finally, the maximum absorbed amounts of cefazolin and vancomycin were established by impregnating 1 g of bone chips with 5 ml of antibiotic solution.
  
  
  RESULTS
  A decrease of the S. epidermidis-free zone was seen with oxacillin and cefazolin solutions stored at 37 degrees C for 1 month, with vancomycin stored at 37 degrees C for 6 months and with cefazolin and oxacillin solutions stored at 20 degrees C for 6 months. The activity of the other antibiotic solutions, pills and impregnated bone chips was not affected by storage. The in vitro dose-response curves show that the free-zone diameter increases logarithmically with antibiotic concentration. The absorbed antibiotic amount of one gram bone chips was determined.
  
  
  CONCLUSIONS
  Storage of antibiotics in frozen form or storage of antibiotic pills at temperatures up to 37 degrees C for 12 months does not affect their activity. However, storage of antibiotic solutions at temperatures above 20 degrees C does affect the activity of some of the antibiotics investigated. The in vitro dose-response curve can be used to determine the optimal concentration(s) for local application. It provides the opportunity to determine the antibiotic content of bone chips, and thus the amount of antibiotics available locally after application.
authors.affiliation: Netherlands Bone bank Foundation, Rijnsburgerweg 10, 2333 AA Leiden, The Netherlands. nmathijssen@bonebank.nl
authors.forename: Nina M C
authors.initials: NM
authors.lastname: Mathijssen
authors.forename: Pieter L C
authors.initials: PL
authors.lastname: Petit
authors.forename: Peter
authors.initials: P
authors.lastname: Pilot
authors.forename: B Wim
authors.initials: BW
authors.lastname: Schreurs
authors.forename: Pieter
authors.initials: P
authors.lastname: Buma
authors.forename: Rolf M
authors.initials: RM
authors.lastname: Bloem
mesh_terms: D000081:Acetamides / Q000737:chemistry / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000627:therapeutic use*; D019072:Antibiotic Prophylaxis; D016025:Bone Transplantation / Q000009:adverse effects / Q000379:methods*; D002437:Cefazolin / Q000737:chemistry / Q000627:therapeutic use; D002981:Clindamycin / Q000737:chemistry / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004339:Drug Compounding; D004355:Drug Stability; D004356:Drug Storage; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000737:chemistry / Q000627:therapeutic use; D023303:Oxazolidinones / Q000737:chemistry / Q000627:therapeutic use; D016459:Prosthesis-Related Infections; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000502:physiology; D013530:Surgical Wound Infection / Q000188:drug therapy* / Q000517:prevention & control; D013696:Temperature; D014184:Transplantation, Homologous / Q000009:adverse effects / Q000379:methods*; D014640:Vancomycin / Q000737:chemistry / Q000627:therapeutic use
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D002981:Clindamycin; D014640:Vancomycin; D002437:Cefazolin; D000069349:Linezolid; D010068:Oxacillin