Tuesday, May 01, 2007

Locally Administered Antibiotics for Prophylaxis Against Surgical Wound Infection

Locally Administered Antibiotics for Prophylaxis Against Surgical Wound Infection
The Journal of Bone and Joint Surgery (American). 2007;89:929-933.doi:10.2106/JBJS.F.00919

An in Vivo Study Seth R. Yarboro, BS1, Elyse J. Baum, BS1 and Laurence E. Dahners, MD1
1 Department of Orthopaedics, University of North Carolina at Chapel Hill, CB 7055, Chapel Hill, NC 27599-7055. E-mail address for L.E. Dahners:

Investigation performed at the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants of less than $10,000 from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

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Background: Currently, the standard for prophylaxis against surgical infection consists of perioperative systemic antibiotics. In this study, we investigated the relative efficacy of various methods of antibiotic delivery for the prevention of surgical wound infections. We hypothesized that sustained release of local antibiotics inside the wound cavity by a drug delivery system would be more effective than systemically administered antibiotics.

Methods: Using a rat model, we inoculated a surgical wound in the quadriceps muscle with 8.0 x 105 colony-forming units of Staphylococcus aureus and then administered one of seven types of treatment: no treatment (control), bacitracin irrigation, calcium sulfate flakes, systemic gentamicin, local aqueous gentamicin, local gentamicin-loaded calcium sulfate flakes, and a combination of local gentamicin-loaded calcium sulfate and systemic gentamicin. The seven treatment groups consisted of ten rats each. To further evaluate a trend, the group treated with systemic gentamicin and the one treated with local gentamicin solution were extended to include twenty-five and twenty-seven rats, respectively. At forty-eight hours postoperatively, specimens from the wounds were obtained for quantitative culture.

Results: The control group, the group treated with bacitracin irrigation, and the one treated with plain calcium sulfate had very high bacterial counts and high mortality rates while the groups treated with gentamicin had low bacterial counts and a 100% survival rate. Local gentamicin was significantly more effective than systemic gentamicin in reducing bacterial counts.

Conclusions: The gentamicin-loaded calcium sulfate flakes did not result in bacterial counts that were significantly lower than those following systemic administration of gentamicin, which refuted our hypothesis. However, gentamicin solution injected directly into the closed wound did result in levels of bacteria that were significantly lower than those following treatment with the systemic gentamicin.

Clinical Relevance: We believe that a high initial concentration of locally applied antibiotic inside the wound effectively kills bacteria present in the wound cavity, where systemic antibiotics have poor penetration, suggesting that this method of antibiotic administration may be a desirable adjunct for prophylaxis against infection in surgical wounds.

The Journal of Bone and Joint Surgery (American)