Objective: The study aimed at determining the ability of lipophosphonoxin DR5026 to inhibit the formation of bacterial biofilm on the bone cement surface and assessing potential development of bacterial resistance.
Material and methods: Bone cement (Hi-Fatigue Bone Cement 2x40, aap Biomaterials GmbH, Germany) was polymerized with lipophosphonoxin DR5026. Cement samples were cultured using bacterial suspension containing Staphylococcus epidermidis CCM7221 at an inoculum density of 106 CFU/mL. After three, 24, and 48 hours of incubation at 35 °C, the number of bacteria adhered to the sample was measured and their growth curve was plotted. In 14 cycles, strains of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Streptococcus agalactiae were exposed to subinhibitory concentrations of DR5026 and the minimum inhibitory concentrations (MICs) were determined.
Results: After three hours of culture in the bacterial inoculum with an initial concentration of 106 CFU/mL, the number of colonies isolated from the cement sample treated with DR5026 was smaller by two orders of magnitude when compared to a control cement sample. After 24 and 48 hours of incubation, the number of CFU remained at 50 in the treated cement, whereas 109 CFU were cultured from control cement samples. The plotted growth curves for bacteria adhered to cements clearly showed the inhibitory effect of lipophosphonoxin on their growth and multiplication, particularly after 48 hours. Following 14 cycles of repeated exposure to subinhibitory concentrations of DR5026, no increase in MICs was noted in the tested strains.
Conclusion: Lipophosphonoxin DR5026 used to treat bone cement was found to have antibacterial effects and to inhibit the formation of bacterial biofilm. Repeated exposure of the tested bacteria to subinhibitory concentrations of the above lipophosphonoxin did not induce their resistance or increase their MICs.Key words: bone cement - joint replacement infections - lipophosphonoxins - antibacterial effect - biofilm.