SLR - November 2018 - Stephanie M. Kane

Local Versus Systemic Antibiotics for Surgical Infection Prophylaxis in a Rat Model

Reference: Sweet FA, Forsthoefel CW, Sweet AR, Dahlberg RK. Local Versus Systemic Antibiotics for Surgical Infection Prophylaxis in a Rat Model. J Bone Joint Surg Am. 2018 Sept 19; 100 (18): e120

Scientific Literature Review

Reviewed By: Stephanie M. Kane, DPM
Residency Program: Bethesda Memorial Hospital, Boynton Beach, FL

Podiatric Relevance: Preoperative use of prophylactic antibiotics has been a standard of care in surgery and has shown a decrease in surgical infection rates. Even with the prophylactic antibiotics, surgical site infection postoperatively is a common complication within surgery. The prevalence of postoperative infection varies with the type of procedure and location. It is also important to note that offending organisms are becoming more resistant to antibiotics and more difficult to treat, and further treatment options may be needed in the future.

Methods: This scientific study evaluated the local application of antibiotic agents compared with intravenous antibiotics for infection prophylaxis for surgery. Methicillin-sensitive Staphylococcus aureus (MSSA) was utilized to inoculate the surgical site of 120 rats. The surgical sites were prepared in a sterile fashion, and a defect was created in the spinous process of the rats that mimicked a laminectomy. A ringed vascular graft was implanted submuscularly, adjacent to the spinous process. Eighty rats were treated with local application of antimicrobials, 20 rats received 15 mg/kg of intrawound vancomycin powder, 20 rats received 15 mg/kg of cefazolin powder, 20 rats received 5 mg/kg of tobramycin powder and 20 underwent dilute 0.35 percent betadine lavage for three minutes. Forty rats total were treated with IV antibiotics. Twenty rats were pretreated with IV cefazolin and 20 with IV vancomycin. One week after surgery, the grafts were removed and cultured.

Results: Local antimicrobial prophylaxis with vancomycin and tobramycin powder for infections in the rat model was superior statistically to the IV antibiotics, local cefazolin and betadine lavage groups. Four out of twenty rats (20 percent) treated with tobramycin and vancomycin local powder groups showed positive cultures for MSSA. Twenty out of 20 (100 percent) rats in both the IV cefazolin and the IV vancomycin groups, as well as the betadine lavage group, had positive cultures for MSSA. Eighteen out of 20 (90 percent) treated with the local cefazolin application had positive cultures for MSSA. Local cefazolin powder had a lower infection rate than IV antibiotics and betadine lavage, however, it was not clinically significant.

Conclusion: Local antimicrobial agents (vancomycin and tobramycin) were more effective at eliminating surgical site contamination than IV antibiotics, cefazolin application and betadine lavage. By utilizing a local application of antimicrobials, the concentration in the area of application is higher than that of systemic antibiotics that rely on diffusion into the soft tissues. Further clinical trials may be needed to further compare IV antibiotics and local antibiotic application in humans. Local antibiotics could be a superior option, or adjunct treatment option, to IV antibiotics and could limit the use of systemic antibiotics, therefore reducing the promotion of resistant organisms.

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