Antibiotic Releasing Biodegradable Sutures for the Prevention of Surgical Site Infections

Although a necessary component of surgery, sutures have been shown to exhibit an affinity for microbial adherence and colonization. The sutures offer a conduit for bacteria directly into the wound and infection can be difficult to treat post-colonization, even with antibiotics that are traditionally very effective. Infections associated with sutures are often difficult to resolve and require extended hospitalization, therapy, or additional surgical procedures. Drug eluting sutures offer a potential solution to this issue. In order to maximize antibiotic delivery, modeling changes in suture size, placement, and concentration could provide valuable information for surgeons and manufacturers to better develop and implant sutures, reducing the number of surgical site infections (SSIs) and thus morbidity and mortality. Using COMSOL software, we first generated both a 2D and a 3D model of MONOCRYL plus antibiotic sutures in the skin. Next, we modeled antibiotic-release and biodegradation by tracing the distance the drug penetrates into the surrounding tissue while the suture and the antibiotic are simultaneously being degraded by the body’s enzymatic processes. Finally, we adjusted the distance between adjacent sutures and suture size to ensure that the minimum inhibitory concentration (MIC) of triclosan for various bacteria strains was met at the wound site, without increasing the difficulty for surgeons to implant the suture. In our model, we showed the dispersion of antibiotics into the surrounding tissue over time, demonstrating up to what time point the sutures are able to maintain at least the minimum effective concentration level of antibiotic. We show that antibiotic levels sufficient enough to inhibit bacterial growth can be reached in complex environments, such as the skin. Based on our 3D model, the maximum spacing between adjacent 4-0 sutures to maintain a MIC for S. aureus for 72 hours after suture implantation is 2 mm. Suture spacing for other strains of bacteria can be determined through our predictive equations. The duration of antibacterial properties increases as the spacing between sutures is decreased, but increasing the initial concentration of triclosan in the suture does not significantly increase the duration of antibacterial properties of the suture. The suture decreases in volume by 45% seven days after implantation in the skin, indicating proper surface erosion and a significant loss in tensile strength after that time. The integrity of the suture is necessary to keep the wound closed over the entire healing period, preventing bacteria from entering through the open site and entering the tissue and subsequently traveling through the bloodstream. In this model, we reinforce in vivo and in vitro studies that suggest the effectiveness of antibiotic releasing sutures by modeling antibiotic concentrations in the skin following suture placement. This model will help surgeons determine the spacing for a variety of commercially available sutures, based on the bacterial inhibition properties required, in an effort to reduce the number of surgical site infections that occur. By ensuring effective distribution of antibiotic, following our developed standards in the surgical suite will reduce the number of surgical site infections, significantly reducing costs, morbidity, and mortality from post-operative infections