Lisa Ovington, PhD, FACCWS, MWC, and medical director of Johnson & Johnson’s Ethicon division, presented a webinar about antibacterial sutures (Plus Antibacterial Sutures) and their use in minimizing infection risks of surgical procedures.
Often there is an underestimation of the risk factor of suture contamination. Despite sterilization and proper surgical skin and surgeon preparation, other factors enter into the possibility of infection. The patient might have inherent risk factors and underlying disease. However, a more prevalent concern centers on the number of bacteria that colonize the epidermal layers of not just the intestinal tract, but also the skin.
In humans, there is a 10:1 ratio of bacteria to cells in the body; it stands to reason there is a similar disparity in animals. Epidermis also lines hair follicles and sebaceous (sweat) glands. Multiple layers of stratum corneum flake off and shed over time; however this shedding does not necessarily eliminate bacteria in the deeper layers, which cannot be reached with standard pre-operative skin preps.
A surgical incision breaches the stratum corneum and releases bacteria from the epidermal appendages into the dermis. Passage of a needle through skin layers additionally traumatizes tissue. And, suture remains as a “foreign body” once a wound has been closed.
Studies from as long ago as 1957 (Elek and Conen) demonstrated that an intradermal injection of Staph pyogenes needs 2-8 million bacteria to create pus. In contrast, only hundreds of S. pyogenes are required to create pus when a piece of suture is present. This represents a 10,000-fold decrease in dose, a likely bacterial inoculation incurred with opening and closing a wound.
Many other studies demonstrate the potentiating effect of a foreign body on infection risk due to bacterial production of biofilms. The presence of infection was correlated with 100% presence of biofilms, whereas only 67% of non-infected devices had biofilms. Researchers found no difference in infection occurrence between monofilament and multifilament suture.
The use of systemic antibiotics might suggest that there is no reason to protect against suture contamination. However, without an intact blood circulation, systemic antibiotics cannot localize efficiently in the surgical site. This type of circulatory interruption occurs when tissue and blood supply are incised during surgery.
The coating on the Ethicon sutures is triclosan, which is an antiseptic that blocks an enzyme that bacteria use to make lipids from the cell membrane. The result is that bacteria cannot proliferate. Triclosan has no impact on animal tissue or wound healing. Challenge of triclosan-coated suture with a broth of S. aureus resulted in resistance of suture to colonization.
Ovington explained that of 50 clinical trials conducted on 19,000 human patients, 48 were done independent of Ethicon. Not all demonstrated a statistically significant decrease in surgical site infections (SSI), which she expressed could be due to the fact that different layers were closed with different techniques. However, 12 of 15 meta-analyses showed a positive response with 22-38% decrease in the risk of surgical infection using triclosan-coated suture. The added cost of less than 60 cents per suture is negligible compared to the cost in hundreds to thousands of dollars to treat a surgical infection.
Veterinary studies have been performed in dogs and horses. Morrison (2016) tested the ability of colonization via S. pseudointermedius in vitro using braided and barbed suture, which increases the surface area for potential bacterial colonization. A two-minute exposure to the Staph broth allows sufficient time for formation of a biofilm. In this study, there was a significant decrease in Staph adherence to the triclosan-coated suture.
A study of equine laparotomy did not demonstrate a difference in incisional complications in 100 horses (Bischofberger 2010) using triclosan-coated suture. However, it was pointed out that in this multi-layer closure, only the subcutaneous layer was closed with triclosan-coated suture.
A study (Stine 2018) looked at 703 dogs with tibial plateau leveling osteotomy (TPLO) procedures. Incidence of implant-associated infection was decreased by 88%; however, many strategies were modified including the use of triclosan-coated suture.
The use of antibacterial suture might be relevant to a number of equine surgical procedures and could be worth looking into further.