Effectiveness of antimicrobial curtains in infection control

Tom Claffey, MD, Director of the Infectious Diseases Division, Maine Medical Center, describes the findings of a new study that highlights the important role that antimicrobial curtains could play in decreasing the transmission of infectious bacteria.

The University of Iowa in the US has been instrumental in providing the latest evidence on the role that soft surfaces – such as hospital privacy curtains – play in infection control. In the April 2012 issue of the American Journal of Infection Control (AJIC),¹ research from the Department of Internal Medicine, in the Carver College of Medicine, revealed that 95% of the curtains examined were contaminated at least once during the study with pathogens such as Staphylococcus aureus (MRSA) and 18 with vancomycin-resistant Enterococcus (VRE).

Moreover, this contamination occurred rapidly – 92% of the freshly laundered curtains hung during the study were contaminated within one week.

Multiple studies have shown the correlation between a cleaner patient environment, lower infection rates and reduced risk of transmission. No matter how diligently a hospital is cleaned and maintained, the AJIC study illustrates that these facilities are so overwhelmed with the number of pathogenic bacteria that it is difficult for staff to keep up.

Now, the most recent findings from the University of Iowa,² indicate that privacy curtains integrated with antimicrobial properties may potentially play a role in removing bioburden from the patient environment. Healthcare facilities may find addressing the soft surfaces of their operations, including curtains, scrubs, sheets and more, is an effective horizontal strategy for addressing healthcare associated infections (HAIs) across the board.

The study was led by Dr Marin Schweizer at the University of Iowa Carver College of Medicine. It was the first of its kind for a privacy curtain with antimicrobial properties. Until then, no other such curtain had undergone and succeeded in a randomised controlled trial (RCT) to assess its effectiveness in a clinical setting.

The double-blinded RCT was conducted in two intensive care units (ICUs) of a tertiary care teaching hospital: a surgical ICU and medical ICU. Both ICUs contained single patient rooms and two-patient rooms. In all, 21 rooms in the surgical ICU and nine rooms in the medical ICU were selected to have either a new, standard curtain or a seemingly identical curtain with antimicrobial properties.

The antimicrobial curtains were designed by PurThread Technologies and are integrated with the company’s proprietary antimicrobial agent.

Curtains were randomly placed by housekeeping staff at the beginning of the trial – 15 rooms received PurThread curtains and 15 rooms received standard curtains. Twelve PurThread curtains and nine standard curtains were placed in the surgical ICU and three PurThread curtains and six standard curtains were placed in the medical ICU.

In terms of the physical quality of the curtains, both the PurThread and standard curtains were woven, made from 100% polyester fibre and pre-washed. The numbers of threads per square inch were the same for both types of curtains.

The hydroxyl radicals attack micro-organisms along several parallel pathways – simultaneously degrading the cell’s protective biofilm, rupturing the cellular membrane, and disrupting the biological processes within the cell

The antimicrobial agent in PurThread’s curtains, incorporated in the fibre while it is molten, produces a chemical species known as hydroxyl radicals. The hydroxyl radicals attack micro-organisms along several parallel pathways – simultaneously degrading the cell’s protective biofilm, rupturing the cellular membrane, and disrupting the biological processes within the cell, thereby killing the pathogen.

The second key component of PurThread’s approach is the proprietary integration technology through which the agent becomes an intrinsic part of every fibre. All synthetic fibres begin as hard resin pellets. These pellets are melted, extruded and emerge from spinnerets as fibres that are thinner than a human hair.

PurThread’s agent is incorporated into the polymer during its molten phase, so that the agent resides not only on the surface of each fibre, but also throughout each fibre down to its core. Unlike topical treatments, this approach minimises leaching and sustains the fabric’s antimicrobial efficacy throughout its useful life. By utilising multiple mechanisms of action, the chances for bacteria to develop resistance to this technology may potentially be reduced.

The University of Iowa researchers collected cultures from all 30 curtains, swabbing them repeatedly over the course of 23 days. Two curtains became visibly soiled during the study period (on days 15 and 16), were removed by healthcare professionals and could no longer be sampled. Thus, a total of 234 cultures were collected.

Study staff donned gloves and washed their hands prior to each sampling. The leading edge of each curtain was cultured with a moist swab from 90cm above the ground to 190cm above the ground, with a 4cm depth, on the front and back side of the leading edge. This area was chosen based on an estimation that this area of the curtain surface was likely to be touched routinely by patients and healthcare professionals. Swabs were tested for Staphylococcus aureus, Enterococcus species and Gram-negative pathogens.

The time to first contamination was also examined. The incidence rate of contamination between PurThread curtains and standard curtains was compared using repeated measures Poisson regression models. The generalised estimating equations (GEE) approach was used to adjust statistically for potential confounding variables. All analyses were performed using SAS software (SAS Institute, Cary, North Carolina, USA) version 9.2.

Housekeeping staff, study staff, healthcare professionals, laboratory personnel and data analysts were all blinded to the curtain randomisation. Blinding was removed only after data analysis.

The results

The median time to first contamination for PurThread curtains was 14 days compared with two days for standard curtains. Thus, the antimicrobial properties of the PurThread curtains displayed a considerably longer resistance to bioburden compared with the standard curtains. Researchers considered this to be statistically significant. The results of the Poisson regression analysis suggested that the overall adjusted rate of contamination was 29% lower in PurThread curtains compared with standard curtains, although after statistically adjusting for ICU type and number of beds per room, this difference was not statistically significant.

Another major find was the fact that the risk of VRE contamination was eight times higher among standard curtains compared with PurThread curtains. Eleven standard curtains contained VRE compared with just one from the PurThread curtains. Additionally over time, PurThread curtains had a median of two unique pathogens, while the standard curtains had a median of three unique pathogens.

Practical significance

In this double-blinded RCT, it was found that privacy curtains embedded with the antimicrobial properties of the PurThread proprietary formula increased the time to first contamination as compared with standard privacy curtains. It took only two days on average for the standard curtains to become contaminated, whereas PurThread curtains lasted up to two weeks. Given the rapidity with which standard privacy curtains became contaminated and the logistical difficulty inherent in changing or disinfecting curtains between patient uses, fabrics that resist contamination could play a significant role in enhancing environmental hygiene.

Given the rapidity with which standard privacy curtains became contaminated and the logistical difficulty inherent in changing or disinfecting curtains between patient uses, fabrics that resist contamination could play a significant role in enhancing environmental hygiene

In laboratory tests recently completed at the University of Iowa, researchers inoculated PurThread fabric and standard control fabric with carbapenem-resistant Klebsiella pneumoniae. Thirty minutes after inoculation, the PurThread sample had 99.96% fewer CR Klebsiella colony forming units than the control fabric. This increased to a 99.9% reduction after two hours and 99.999999% after 24 hours (note: this data reflects the results of specific in vitro laboratory testing and the US Environmental Protection Agency has not reviewed these results for healthcare claims – results in the clinical environment may vary depending upon the conditions in each environment).

As the pressure to reduce HAIs increases, we can expect more infection control products to flood the market. In a time of high standards, rigorous science and clinical efficacy, research studies such as the one described here are likely to be established as the new normal for any product looking to prove that it is a continuously-active surface and protective barrier against bioburden transmission. Today’s evidence-based medicine, clinical pathways and medical investment decisions depend upon such data, and the RCT of PurThread curtains is leading the way for the medical textile industry.

References

1. M. Ohl, M. Schweizer, M. Graham, K. Heilmann, L. Boyken, D. Diekema. Am J Infect Control. 2012 Dec; 40(10):904-6. doi: 10.1016/j.ajic.2011.12.017. Epub 2012 Mar 30.

2. M.Schweizer, M. Graham, M. Ohl, K. Heilmann, L. Boyken, D. Diekema, Infection Control and Hospital Epidemiology 33 11 (November 2012), 1081-1085