Comparative evaluation of the antibacterial activity of bone allografts impregnated with various antibiotics

Background. Radical surgical debridement is the most important condition for the successful treatment of patients with chronic osteomyelitis. However, since even the most meticulous debridement cannot guarantee complete eradication of the pathogen, local antibacterial therapy becomes of key importance. This underscores an urgent clinical need for the development of an osteoplastic biodegradable material with prolonged antimicrobial activity. One of the most promising options is a purified allogeneic bone-based material. The aim of the study — to perform a comparative evaluation of the duration of the antibacterial activity of allografts impregnated with different antibiotics against Gram-positive and Gram-negative bacteria. Methods. Purified and delipidized bone allografts measuring 5×5×5 mm were prepared according to the procedure developed by the authors. The bone blocks were impregnated with antibacterial agents with varying activity spectra: vancomycin, aztreonam, meropenem, and fosfomycin. The presence and duration of antibacterial activity of the obtained samples were determined against reference bacterial strains depending on the drug’s spectrum of activity by applying a 24-hour incubation solution containing the samples to the surface of a bacterial lawn. The data were analyzed using GraphPad Prism 9.0. Results. Applied standard vacuum impregnation protocol ensured reproducible saturation of bone tissue with antibiotics. The greatest increase in mass was observed after impregnation with aztreonam, whereas the smallest increase was noted after impregnation with fosfomycin. Vancomycin-impregnated blocks were most active against methicillin-sensitive and methicillin-resistant S. aureus. Meropenem-impregnated blocks were effective for 4 days against K. pneumoniae. Impregnation with aztreonam provided antibacterial activity against K. pneumoniae for up to 6 days. Fosfomycin-impregnated blocks were active against Gram-negative pathogens for 6 days. Conclusion. The developed technique was shown to ensure the antibiotic loading of the bone substitute material and drug release over several days, with the most prolonged effect observed following impregnation with vancomycin and fosfomycin. Further optimization of osteoplastic materials processing methods is needed, as well as testing other potential antimicrobial agents in combination with antibiotics to overcome potential pathogen resistance.