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Updated: Dec 28, 2025
In Vivo Mouse Model of Spinal Implant Infection
Published on: June 23, 2020
Topical vancomycin for treatment of methicillin-resistant Staphylococcus epidermidis infection in a rat spinal
Melissa J Karau1, Chenghao Zhang2, Jayawant N Mandrekar3
1Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, 55905, USA.
Study Design:
Basic science.
Objective:
Investigate the ability of local applicaiton of vancomycin, either in powder form or suspended within poly(lactic-co-glycolic acid) microspheres (MS), to treat infection using a rat spinal model. Surgical site infections (SSIs) are a serious complication after spine surgery and are associated with high morbidity and mortality and often caused my coagulase negative staphylococci. A comprehensive approach to reduce SSIs has been recommended including the use of topical vancomycin. Animal and human studies have shown improved control of infection with local compared to systemic antibiotics.
Methods:
K-wires seeded with methicillin-resistant Staphylococcus epidermidis RP62A (MRSE) were treated with vancomycin powder, carboxymethylcellulose sodium salt (CMC) (microsphere carrier), vancomycin powder, blank MS or vancomycin-loaded MS for 24 or 48 h in vitro after which bacteria were enumerated. In addition, a spinal instrumentation model was developed in rats with a bacterial seeded K-wire implanted into the right side of L4 and L5. Rats underwent no treatment or were treated locally with either vancomycin powder, blank MS or vancomycin-loaded MS. After 8 weeks, the K-wire, bone, soft tissue and wire fastener were cultured and results analyzed.
Results:
Vancomycin powder and vancomycin-loaded MS resulted in significantly fewer bacteria remaining in vitro than did CMC. Vancomycin powder- treated animals' cultures were significantly lower than all other groups (P < 0.0001) with negative culture results, except for one animal. The vancomycin-loaded MS-treated animals had lower bone bacterial counts than the controls (P < 0.0279); blank MS-treated animals had no differences in bacterial densities when compared to non-treated animals.
Conclusion:
Vancomycin powder and vancomycin-loaded MS were active against MRSE in vitro, in a rat MRSE implant model; however, vancomycin MS were inferior to the topical vancomycin powder. Vancomycin powder prevented MRSE infection in a rat spinal implant infection model.
Insights
Topical vancomycin powder effectively prevented methicillin-resistant Staphylococcus epidermidis (MRSE) spinal implant infections in rats. Vancomycin microspheres showed activity but were less effective than vancomycin powder.
Area of Science:
- Basic science research
- Infectious disease modeling
- Biomaterials science
Background:
- Surgical site infections (SSIs) are a significant complication following spine surgery, often caused by coagulase-negative staphylococci.
- Local antibiotic application, particularly topical vancomycin, is recommended to reduce SSIs.
- Previous studies suggest local antibiotic delivery is more effective than systemic administration.
Purpose of the Study:
- To evaluate the efficacy of locally applied vancomycin, in powder or microsphere form, for treating implant-associated infections.
- To compare vancomycin powder and poly(lactic-co-glycolic acid) microspheres (MS) in a rat spinal infection model.
Main Methods:
- In vitro testing of vancomycin powder and vancomycin-loaded MS against methicillin-resistant Staphylococcus epidermidis (MRSE).
- Development of a rat spinal instrumentation model with MRSE-seeded K-wires.
- Local treatment of infected rats with vancomycin powder, blank MS, or vancomycin-loaded MS.
Main Results:
- Both vancomycin powder and vancomycin-loaded MS reduced bacterial load in vitro.
- Vancomycin powder treatment resulted in significantly lower bacterial counts in vivo compared to all other groups, with most animals showing negative cultures.
- Vancomycin-loaded MS significantly reduced bone bacterial counts compared to controls, but were less effective than vancomycin powder.
Conclusions:
- Vancomycin powder and vancomycin-loaded MS demonstrate in vitro and in vivo activity against MRSE.
- Topical vancomycin powder was superior to vancomycin microspheres in preventing MRSE infection in a rat spinal implant model.
- Vancomycin powder is a highly effective treatment for preventing MRSE spinal implant infections.
