As we enter World AMR Awareness Week for 2024, there is an increasing recognition that we are coming towards the end of antibiotics in some settings. Prevention is undoubtedly better than cure. Developing whole new classes of antimicrobial agents is unlikely to dig us out of the AMR mire, but getting better at preventing them is a hugely important part of our response to the AMR threat. Into this context lands today’s study – a randomised intervention study on the impact of introducing an antimicrobial surface coating in an Emergency Department setting. The results were positive, with the antimicrobial surface coating associated with lower levels of microbial contamination. Does this prompt a rethink of our approach to surface disinfection? A reminder that this paper will be the subject of tomorrow’s Journal Club (register here).

Antimicrobial surfaces have been around for ages. In ancient history people recognised that some materials had a helpful preservative quality long before Germ Theory came along. There have been quite a few promising studies showing that antimicrobial surfaces of various kinds have been implemented safely and effectively in healthcare settings, have demonstrated a reduction in microbial contamination, and that this has translated into a reduction in transmission. Whilst cleaning and disinfection of surfaces in healthcare settings has been shown to be an effective intervention to reduce the transmission of significant pathogens, it has (at least!) two fundamental challenges. Firstly, it relies on human beings to actually clean and usually disinfect surfaces and human beings are not always reliable. (Even automated room disinfection systems still rely on human beings to clean the space effectively before disinfection.) Secondly, it can never be a continuous process – the level of contamination will rise steadily between cleaning and disinfection episodes, however effectively and frequently they occur. Hence the space for antimicrobial surfaces to flourish – by (to a degree) complementing the inadequacy of routine cleaning and disinfection, and by acting continuously to address surface contamination.

Today’s study set out to evaluate the impact of a novel antimicrobial surface coating (NOMOBAC) in an Emergency Department (ED) setting in Singapore over 6 months in 2018/19. NOMOBAC is a modified acrylate and silane that produces continual non-exhaustive and non-leaching biocidal activity. This single centre, double-blind, placebo-controlled trial was conduced in the ED of a large 1,200 bed hospital in Singapore. Following a pilot evaluation, the right hand rail of the patient transport stretcher was selected for study since it had the highest frequency and duration of touch. All 96 patient transport stretchers were treated with either placebo or NOMOBAC, randomised 1:1. All stretchers were sampled after routine cleaning and immediately before NOMBAC application as a baseline, and then immediately after patient use and before routine cleaning at 24h, 7d, and 180d after application.

Key findings

• The median total aerobic counts were not significantly different at the baseline sampling point. 28.1% the stretchers exceeded 2.5 CFU/cm² despite routine cleaning at baseline.
• Median total aerobic counts were significantly lower on the coated rails at the 24 hour sampling point (0.61 vs. 1.01 cfu / cm²), but not significantly different at the 7 day or 180 day sampling points.
• The median count of Gram-negative bacteria was significantly lower on the coated rails at the 24 hour sampling point), but not at 7d or 180d. The median count of Gram-positive bacteria was lower at all sampling points, but not significantly so.
• The proportion of stretchers exceeding 2.5 cfu / cm² was not significantly different at any of the sampling points.
• MRSA was identified on 20% of rails at baseline, but not at the 24 hr, 7d, or 180d sampling points to detect any differences. MRSA was detected on 50 out of 143 (35.0%) pre-routine-cleaning, post-patient-use, non-intervention stretcher rails.

Limitations and discussion points

• Study design. This is a very impressively designed RCT, including double-blinding and placebo-control.
• ED setting. The study was undertaken in an ED setting. This environment is probably one of the most challenging for an antimicrobial surface coating, due to high patient turnover, high levels of human traffic, and ‘robust’ treatment of surfaces.
• MRSA prevalence. There was a surprisingly high level of MRSA identified, with 20-30% of rails contaminated at various stages of the study. This is a much greater proportion than I’d expect to see in the UK settings. MRSA prevalence in Singapore is high in other studies too, so perhaps not so surprising.
• Lack of microbial coverage. The microbiological sampling methodology didn’t include many of the antibiotic-resistant Gram-negative bacteria that are important to us (e.g. CPE, Acinetobacter) and the same for Gram-positives (especially VRE). It also didn’t include C. difficile spores.
• No clinical outcomes. A major limitation of this study is that patient outcomes were not measured in terms of microbial transmission or HCAI.
• Which antimicrobial surface? There is a huge and frankly overwhelming choice of options to making a surface have antimicrobial properties in terms of improved cleanability, reduced deposition, and direct antimicrobial activity. Some of the options are covered in the Imperial College London white paper that I was involved in producing a few years ago.
• Durability. This study highlighted issues with durability of the antimicrobial surface coating, with only three (6.4%) of the intervention rails having visibly intact coating at 7 days. Related to this, there are big questions around the frequency and method of application. If you need to reapply an antimicrobial coating every hour, it’s not going to work!
• Safety and acceptability. How to we assure ourselves that antimicrobial surfaces are safe and acceptable to patients and staff? The coating used in this study was FDA approved – but this will not be true of all coatings.
• Relationship with cleaning and disinfection. How do antimicrobial surface coating options sit alongside routine cleaning and disinfection? They are part of the same approach (i.e. to reduce environmental contamination in order to maximise patient safety). But there is potential tension between them if, for example, surface cleaning or disinfection damages the antimicrobial surface coating. On the other hand, introducing an “always active” antimicrobial surface might reduce the perceived need for routine surface cleaning and disinfection.
• How good is good enough? How do we know the level of effectiveness that is required in an antimicrobial surface to result in a meaningful reduction of the micro-organisms that can cause HCAI and perpetuate AMR? There is evidence from other studies that introducing antimicrobial surfaces reduces the risk of HCAI.

So do we need to rethink our approach to surface cleaning and disinfection? On the basis of this study, no. The lack of patient outcomes in this study hampers our ability to really get to the bottom of its meaning. However, there are other studies that do show improvements in patient outcomes linked to the introduction of antimicrobial surfaces. I think we need comparative effectiveness studies to help us to understand which antimicrobial surface technology to go for in various settings, and healthcare economics to help us to understand whether the numbers add up.

Finally, a reminder that today’s study will be the subject of tomorrow’s Journal Club. Weds 20th November, 1000 EST / 1500 GMT (UK). Register here!