Quantification of Staphylococcus aureus adhesion to equine bone surfaces passivated with Plasmalyte and hyperimmune plasma.

This research article explores how Staphylococcus aureus bacteria adhere to different bone surfaces in horses. The study also investigates the difference in bacterial adhesion when the bone surfaces are treated with a balanced polyionic solution or hyperimmune equine plasma.

Methods and Execution

• The study is based on an in-vitro comparative study method, which uses bone surface explants from nine equine cadavers.
• A section of the periosteum was removed from a third metacarpal bone (MC3) and attached to sterile stainless steel screens. Three bone surface explants were then cut to present subperiosteal bone, cut cortical bone, or endosteum.
• The bone surfaces were immersed for an hour in Plasmalyte – a balanced polyionic solution, or hyperimmune equine plasma, often used to treat infections.
• The surfaces were then inoculated with Staphylococcus aureus bacteria and incubated for 6 hours. After this, gentle rinsing removed non-adherent bacteria. The surfaces were sonicated to loosen the remaining bacteria.
• The number of bacteria that remained adhered to the bone surfaces was determined through serial dilutions of the sonicate. Scanning Electron Microscopy (SEM) was performed to confirm the bacterial removal by sonication and support culture results.

Results

• The researchers found that less Staphylococcus aureus adhered to the periosteum than to the cortical bone, the cut cortical bone, and endosteal surfaces.
• The study also revealed that treatment with hyperimmune plasma resulted in reduced bacterial adherence compared to treatment with Plasmalyte. This conclusion was supported by SEM imaging.

Conclusions and Implications

• The main takeaways from the research are that periosteum shows less bacterial adherence than other bone surfaces, and that hyperimmune plasma reduces bacterial adhesion to all bone surfaces.
• Understanding these factors that affect bacterial adhesion to bone can potentially assist the development of more effective intraoperative lavage solutions, reducing the risk of postoperative infection, and so improving patient outcomes.