Evading the host response: Staphylococcus "hiding" in cortical bone canalicular system causes increased bacterial...

Area of Science:

• Orthopedic Surgery
• Infectious Disease
• Biomaterials Science

Background:

• Limb salvage surgery is increasingly preferred over amputation for extensive bone loss.
• The choice between metal and allograft bone for void filling remains debated, with infection risk previously considered similar.
• Emerging data suggest Staphylococcus aureus may infect bone via the host lacunar-canaliculi network, potentially impacting infection rates.

Purpose of the Study:

• To investigate the differential infection characteristics of Staphylococcus aureus in cortical allograft bone versus metal implants.
• To elucidate the mechanism of bacterial evasion of host immunity within bone microarchitecture.
• To provide translational insights into osteomyelitis and allograft infection treatment.

Main Methods:

• A longitudinal murine model was used to compare infection in cortical allograft bone and metal implants.
• Real-time quantification of bacterial burden was performed.
• Microarchitecture analysis and host immune response assessment were conducted.

Main Results:

• Cortical allograft bone demonstrated an orders-of-magnitude higher bacterial burden compared to metal and cancellous bone.
• Immune-evading microabscesses were observed within the haversian canal and canaliculi network of infected cortical allograft bone.
• A mechanism for Staphylococcus aureus evasion of host immunity within bone was identified.

Conclusions:

• Cortical allograft bone serves as a significant reservoir for bacterial growth and immune evasion.
• These findings suggest a higher risk of infection with allograft bone compared to metal implants in limb salvage procedures.
• The study necessitates a re-evaluation of current treatment strategies for osteomyelitis and allograft infections.