Making the Case for Textiles with a Dual Mechanism of Action

To the Editor—The paper titled “A Randomized Crossover Trial to Decrease Bacterial Contamination on Hospital Scrubs” ¹ by Mallory Boutin et al published in November’s issue is an important contribution to the body of evidence needed for the use of technical or engineered textiles as an innovative approach to healthcare-system–based infection prevention. I applaud the authors for making such an important step forward for us as a scientific community as we explore new technologies that hold promise for positive impact not only for patients and healthcare workers but also for public health.

In Ms. Boutin’s discussion section, it appears that she and her colleagues have inaccurately interpreted the available published research. She states in her discussion, as it relates to her research, that “(o)ther recent studies testing antimicrobial scrubs but using different products have shown similar ineffectiveness.” On the contrary, the study of reference (Bearman 2012 ² ) concluded that the technology they studied was effective.

In short, Bearman et al conducted a randomized clinical trial (RCT) to determine the effectiveness of a breathable, antimicrobial, fluid barrier scrub fabric for reducing the bacterial burden on hands and scrub attire worn by healthcare workers (HCWs) in an intensive care unit (ICU) setting. The technology Bearman et al studied was an active barrier textile, one with a dual mechanism of action of both fluid repellency and antimicrobial attributes. All study participants (N=31 HCWs) were required to wear an assigned set of scrub attire during a clinical shift. Each HCW underwent unannounced weekly garment and hand cultures. Cultures (N=3,324) taken at the beginning and end of the shifts included garment cultures taken from the abdominal and leg pockets of the scrub attire.

The researchers found a highly significant statistical (P=.0002, .0056) 4–7 mean log reduction in the overall number of methicillin-resistant Staphylococcus aureus (MRSA) CFUs on study scrub attire compared with traditional nonprotective scrub attire worn by HCWs on both the leg and the abdomen. The reduction persisted from the beginning to the end of work shifts.

As Ms. Boutin correctly summarizes, there were no differences in the number of CFUs for vancomycin-resistant Enterococcus (VRE) and Gram-negative rods—not because the study scrubs were not effective, but because the baseline measurements at their facility were too small to measure a statistically significant change. The researchers concluded that “When bundled with known infection prevention strategies such as hand hygiene, antimicrobial impregnated apparel may limit the bacterial burden of the inanimate environment. For settings with high rates of hospital-acquired infections with drug-resistant pathogens such as MRSA, the use of antimicrobial apparel may be a useful adjunct to other infection prevention measures.”

It is also important to note that Bearman’s findings in the clinical setting were validated in the laboratory findings of Hardwick et al. ³ Dr. Hardwick and colleagues described the dual mechanism of action of breathable, antimicrobial, fluid barrier fabrics in their published laboratory “Fabric Challenge” test method. Hardwick noted that the combination of an organo-silane antimicrobial agent and a hydrophobic barrier chemistry provides an additive effect when combined and results in a higher reduction of MRSA on the fabric than does either the antimicrobial or the fluid barrier alone. The role of the fluid barrier in this dual mechanism is consistent with the CDC/HICPAC Guideline for Disinfection and Sterilization in Healthcare Facilities (2008), which states that organic matter in the form of serum, blood, pus, or fecal or lubricant material can interfere with the antimicrobial activity of disinfectants. The bioburden reduction results of Hardwick’s study strongly correlate with the findings of Bearman and colleagues.

To Ms. Boutin’s credit, she is correct regarding textiles with an antimicrobial alone. This was supported in a study conducted by Burden et al ⁴ in which the extent of bacterial contamination of scrub attire and skin were compared when HCWs wore 2 different types of antimicrobial scrub attire compared to traditional nonprotective scrub attire (N=105). One type of antimicrobial scrub attire was made from a polyester microfiber embedded with an antimicrobial chemical. The second type of antimicrobial scrub attire was made from a polyester/cotton blend that included two proprietary chemicals and silver embedded into the fabric. Cultures of the pocket, sleeve cuff, thigh, and wrist were taken before the scrub attire was donned and at the end of the day after patient care. The researchers found that, at the end of an 8-hour work day, wearing the antimicrobial scrub attire did not decrease bacterial or antibiotic-resistant microbial contamination of the HCWs’ scrub attire.

In another study of silver impregnated scrubs versus standard scrubs, Gross et al ⁵ conducted a study in the emergency medical setting to compare the contamination rates of newly developed silver thread-hybrid clothing with that of standard textile clothing. Samples were taken from jackets and pants of 10 emergency workers at day 0 (preservice), day 3 after use, and day 7 after use over a divided 4-week period to test this hypothesis. No significant difference in the extent of microbial contamination was detected between these 2 materials.

These studies suggest that the presence of a fluid barrier, the type of fabric, the active antimicrobial ingredient, the onset of action, kill time, and nonleaching characteristics of the fabric and technology should be carefully assessed to ensure effectiveness and safety. This is, as Ms. Boutin points out, definitely an issue that warrants further research.