Efficacy of Using Sutures Treated with Povidone-Iodine or Chlorhexidine for Preventing Growth of Staphylococcus and Escherichia coli

Sir

Suture-site infections occur in nearly 3 percent of all surgical procedures and increase mortality, morbidity, hospital stay, and costs.¹ It has been hypothesized that sutures themselves aid bacteria in infecting suture sites and serve as an infection reservoir. An effective bactericidal suture treatment that reduces suture contamination would be a promising approach to decrease suture-site infections. Vicryl Plus (Ethicon, Inc., Somerville, N.J.) sutures with triclosan have been shown to inhibit the growth of Staphylococcus aureus, Staphylococcus epidermidis, methicillin-resistant S. aureus, and methicillin-resistant S. epidermidis in vitro and in animal wound models.^2,3 However, Vicryl Plus sutures have not been shown to prevent suture-site infections.

It is proposed here that normal sutures soaked preoperatively in other antiseptics could create a zone of inhibition and thus possibly prevent suture-site infections. Though first mentioned in a plastic surgery procedure,⁴ no study has directly examined the antibacterial capacity of this treatment. The current study evaluates the in vitro effectiveness of sutures treated with povidone-iodine or chlorhexidine in creating a zone of inhibition versus methicillin-resistant S. aureus, methicillin-sensitive S. aureus, S. epidermidis, or Escherichia coli, which constitute nearly half of all causative organisms in suture-site infections.¹

One common negative control (an untreated Vicryl suture) and one common positive control (Vicryl Plus) were placed in each plate. Braided nylon, nonbraided nylon, silk, and Vicryl (size 3-0; Ethicon) sutures were aseptically cut into 1-cm pieces and treated separately with 7.5%, 3.75%, and 1.88% povidone-iodine solutions or 4%, 2%, and 1% chlorhexidine solutions diluted in sterile double-distilled water. An untreated suture of the same type was used as a negative control in each plate. Treated sutures were placed with the controls onto tryptic soy agar plates carrying lawns of 10⁷ colony-forming units of methicillin-sensitive S. aureus, methicillin-resistant S. aureus, or S. epidermidis. Staphylococcus strains were provided by Dr. Greg Somerville, University of Nebraska. The same arrangement was used with LB plates carrying lawns of 10⁷ colony-forming units of E. coli (HB101 strain). Growth was then allowed for 24 hours at 37°C. Trials were performed in triplicate. Zones of clearance were documented (Figs. 1 through 3); t tests were used to determine whether differences in zones of inhibition were significant.

Fig. 1.: Vicryl sutures treated with chlorhexidine in E. coli versus Vicryl Plus. CNC, common negative control (normal Vicryl); CPC, common positive control (Vicryl Plus); 1, 2, 3, and 4, normal Vicryl sutures treated with 4%, 2%, 1%, and double-distilled water volume/volume chlorhexidine.

Fig. 2.: Vicryl sutures treated with chlorhexidine in methicillin-resistant S. aureus versus Vicryl Plus. CNC, common negative control (normal Vicryl); CPC, common positive control (Vicryl Plus); 1, 2, 3, and 4, normal Vicryl sutures treated with 4%, 2%, 1%, and double-distilled water volume/volume chlorhexidine.

Fig. 3.: Vicryl sutures treated with povidone-iodine in methicillin-sensitive S. aureus versus Vicryl Plus. CNC, common negative control (normal Vicryl); CPC, common positive control (Vicryl Plus); 1, 2, 3, and 4, normal Vicryl sutures treated with 7.5%, 3.75%, 1.875%, and double-distilled water volume/volume povidone-iodine.

Assay results are given in Tables 1 and 2. When compared with Vicryl Plus, chlorhexidine-treated sutures had a larger zone of inhibition versus E. coli (braided nylon and Vicryl), and an equivalent zone of inhibition versus methicillin-resistant S. aureus (Vicryl), S. epidermidis (braided nylon, nonbraided nylon, and Vicryl), and E. coli (nonbraided nylon and silk). All povidone-iodine–treated sutures had smaller zones of inhibition.

Table 1: Zones of Inhibition with Chlorhexidine (4.0% v/v) (diameter in mm)

Table 2: Zones of Inhibition with Povidone-Iodine (7.5% w/v) (diameter in mm)

In operations where E. coli is the most likely pathogen (e.g., gastrointestinal, perineal), chlorhexidine-treated sutures could be more effective in preventing suture-site infections than Vicryl Plus sutures. Also, given their equivalent zones of inhibition versus methicillin-resistant S. aureus and S. epidermidis, chlorhexidine-treated sutures may be as effective as Vicryl Plus in other procedures where staphylococci are the causative pathogens. Of note, zones of inhibition have not been shown to correlate directly with suture-site infection prevention. We plan to carry out additional studies using an animal wound model to examine the in vivo efficacy of this approach.

Glenn Walker, B.S.

Texas A&M Health Science Center College of Medicine

Temple, Texas

Malcolm Rude, M.D.

Bryan, Texas

Suat L. G. Cirillo, Ph.D.

Jeffrey D. Cirillo, Ph.D.

Department of Microbial and Molecular Pathogenesis

Texas A&M Health Science Center College of Medicine

College Station, Texas

DISCLOSURE

None of the authors has a financial interest or commercial association with any of the subject matter or products mentioned in this article.