a lysis zone
I.A. Kirilova, V.T. Podorozhnaya
Introduction of drugs directly to an extensive bone defect by injection does not ensure their long-term pres-ence in a zone of bone lesion and prolonged osteogenic stimulation. Therefore the drugs should be delivered with a carrier capable to absorb and gradually release them in the course of time.
We have suggested a biological carrier on the basis of dispersed allografts, which are capable to retain the drugs. Bacteriological experiments were carried out to study duration of release of various drug doses from this carrier. A carrier containing one of the antibacterial drugs Ciprofloxacin or Cefazolin was intro-duced in a solid Muller-Hint nutrient medium with a pathogen (Staphylococcus aureus, Pseudomonas aeruginosa or Escherichia coli) at a concentration of 2,5×107 CFC/ml.
Interpretation of antibiotic susceptibility data are based on relationship between a size of a pathogen growth inhibition zone around the carrier and minimally suppressing concentrations of corresponding anti-biotics against the same pathogen.
The experiment shows that active elimination of Ciprofloxacin and Cefazolin occurred during 14 days. Within this period a lysis zone runs up to 28 mm for Staphylococcus aureus, 32 mm - Pseudomonas aeruginosa, and 27 mm - Escherichia coli. By 21 days of observations a diameter of zones of pathogen growth inhibition remained within 21-23 mm in spite of some decrease in lysis zone for all cultures. This testifies to preservation of local antibiotic activity of the carrier.
The analysis of experimental data suggests that a biological carrier containing antibacterial drugs releases sufficient quantity of these agents to provide local antibacterial effect during 21 days under a load
of 2,5х107 CFC/ml. The experiment revealed that an effective dose is 10 times lower then a therapeutic one. The carrier itself, being a dispersed allograft, promotes stimulation of reparative processes in a zone of bone lesion.