Introduction: The effect of different temperatures to antibiotics is unknown. What is the dose-response curve of bone chips impregnated with different kinds of antibiotics?

Material and Methods: Five different antibiotic pills and solutions (cefazolin, clindamycin, linezolid, oxacillin, vancomycin) were stored at −80°C, −20°C, 4°C, 20°C and 37°C. Also, bone chips were impregnated with cefazolin and vancomycin solution and were stored at −80°C and −20°C. After 1 month, 6 months and 1 year, reaction of the antibiotics to Staphylococcus epidermidis was measured using an inoculated iso-agar. Activity of the antibiotics was measured as the diameter of the Staphylococcus epidermidis-free zone.

Also, five cefazolin and vancomycin solutions were used to impregnate bone chips and to make dose-response curves. Furthermore, 1 gram bone chips was impregnated with 5ml cefazolin or 5ml vancomycin solution.

Results: A decrease of the diameter free zone Staphylococcus epidermidis was seen when oxacillin and cefazolin solutions were stored at 37°C for 1 month and when vancomycin was stored for 6 months (37°C). Also, when cefazolin and oxacillin solutions were stored at 20°C, a decrease was noticed. The storage of other antibiotic solutions, pills and bone/antibiotics composite showed no differences in reaction. Dose-response curves show that with increasing antibiotic quantity, diameter free zone increases according to a logarithmic function.

Conclusion and discussion: With the dose-response curve the optimal concentration(s) for local application can be determined. It gives the opportunity to determine the amount of antibiotics present in the patient locally. Freezing of antibiotics does not affect the activity of the investigated antibiotics.