What healthcare workers should know about environmental contamination


A useful summary of current evidence highlights what healthcare workers should know about environmental contamination in hospitals. Whilst the focus of the article in the ICU, the principles are the same for healthcare workers in other settings too. Bacteria contaminate the inanimate environment; this contributes to patient acquisition of pathogens; biofilms play an important but uncertain role; and improved disinfection methods are now warranted.

Bacterial contamination

Key pathogens are shed into the hospital environment. This included MRSA, VRE, C. difficile spores, resistant Gram-negative bacteria (especially Acinetobacter baumannii), and other microbes including fungi and viruses. If not actively killed or removed, they can survive for months and months (or decades in the case of spores). Patients with symptoms tend to shed more than patients who are colonised only, but even asymptomatic carriers shed into the hospital environment. The environmental sites that are closest to patients tend to be more heavily contaminated; and this can result in the acquisition of pathogens on the hands of healthcare workers.

Clinical impact

For many years, the scientific community questioned whether all this environmental contamination was cause or effect of patient infection and colonisation with these hospital pathogens. The most powerful evidence that environmental contamination is a cause of HCAI comes from the epidemiological findings that patients admitted to rooms previously occupied by patients with a hospital pathogen are roughly twice as likely to acquire these pathogens. Furthermore, improving the effectiveness of hospital cleaning and disinfection mitigates this increased risk, reinforcing that environmental contamination has important clinical impact.

Biofilms lurking

A few years ago, biofilms were first identified on dry hospital surfaces. This was a surprise: previously biofilms had been associated with the wet surfaces in aqueous environments (e.g. ships hulls and teeth)! This finding has important implications: biofilms could explain the extraordinarily long survival time of non-spore forming bacteria on dry hospital surfaces, and why they are so difficult to kill. Bacteria embedded in biofilms can be hundreds or even thousands of times less susceptible to disinfectants.

Improved disinfection

All of this argues for improved disinfection. There’s a lot that we can do to improve the efficacy of existing materials and methods. For example, using fluorescent markers can help to highlight areas that are not being cleaned effectively. Pre-impregnated disinfectant wipes are a useful innovation, making cleaning faster, more convenient, safer for staff, and reducing the risk of incorrectly formulated disinfectants being used. And automated room disinfection systems (such as those based on hydrogen peroxide and UVC) have been shown to achieve higher levels of surface hygiene than conventional methods, which translates into improved patient outcomes.


Is your wipe really sporicidal?


Sporicidal disinfectant wipes are being used increasingly for tackling surfaces contaminated with C. difficile spores in hospitals. A wide range of ‘sporicidal’ wipes are coming onto the market. However, concerning published data shows that some wipes marketed as being ‘sporicidal’ do not have meaningful activity against spores when tested under controlled laboratory conditions. This blog outlines three key questions that you should be asking when a company comes to you with a ‘sporicidal’ wipe: is it plausible that the chemicals in the wipe will have sporicidal activity? Does the laboratory data provided by the manufacturer support their claims? Were the tests performed in a reputable, accredited laboratory? If the answer to any of these questions is no, then your wipe probably isn’t sporicidal and you should look for an alternative!

There is rapidly accumulating evidence that disinfectant wipes out-perform ‘bucket’ methods for disinfection. They are more convenient, assure the correct concentration of disinfectant, are safer for users, and make it easier to achieve an appropriate contact time. A particular challenge in hospitals is disinfecting surfaces that may be contaminated with C. difficile spores, or clinical areas that have been used to treat diarrhoea and vomiting where a pathogen has not been identified. Wipes with sporicidal activity can help to reduce the transmission of C. difficile in hospitals. So disinfectant providers have responded by developing a whole range of sporicidal wipes. The problem is that some of these wipes have very limited or no sporicidal activity. This blog aims to help users in negotiating a complex marketplace of sporicidal wipes using three simple questions:

  • Is it plausible that the chemicals in the wipe will have sporicidal activity?
    We know from centuries of research that some chemicals, notably oxidising agents (for example peracetic acid, hydrogen peroxide and hypochlorites) have sporicidal properties when in the right formulation and at the right concentration. However, other chemicals do not have sporicidal activity, notably quaternary ammonium compounds even when combined with triamines, even though suboptimal testing methods, particularly when neutralising the agents may provide the apprearance of sporicidal activity. GAMA produce such a wipe and would never claim sporicidal activity.
  • Does the laboratory data provided by the manufacturer support their claims?
    There is no current European standard test for sporicidal efficacy in the healthcare sector. In lieu of a more appropriate test, healthcare disinfectant manufacturers often use EN 13704, but a Joint Working Party from the Healthcare Infection Society (HIS) and the Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infections (ARHAI) of the Department of Health England recommended that it requires significant modification to evaluate sporicidal activity in conditions reflective of a healthcare environment. Therefore, passing laboratory tests based on these Working Party guidelines should be regarded as the minimum standard for a sporicidal wipes to be used in healthcare settings.
  • Were the tests performed in a reputable, accredited laboratory? Even if the laboratory data tick all the right boxes and the wipe seems to exhibit sporicidal activity, it’s important to ensure that there is assurance that these data are robust and that the testing laboratory is accredited. Laboratories that state that they are ‘working towards’ ISO and UKAC accreditation are therefore not accredited. This is not to say that non-accredited labs are always inferior or inaccurate, as many well-respected University and Hospital research labs are not accredited. It’s just that laboratory accreditation is designed to ensure that standard tests are performed in a standardised way so that everybody can rely on the results.

GAMA has produced a Sporicidal Wipe based on peracetic acid. Peracetic acid has long been known to have sporicidal properties, the wipe has been tested using appropriate methods in independent, accredited laboratories and also in respected university laboratories. If you’d like to have some more detailed information on this issue, or you’d like to speak with an expert at GAMA (or we can put you onto an independent expert), please get in touch.


Further intel on disinfectants and antiseptics for Candida auris

We posted a week or two ago about a study evaluating the efficacy of various antiseptics and disinfectants for addressing Candida auris. A similar study published recently presents similar findings: chlorine-based disinfectants, and iodine-based and chlorhexidine-based antiseptics all have a role to play in tacking C. auris.

The lab study collected a range of C. auris isolates, including some multidrug-resistant strains, and performed a quantitative suspension test (EN 13624:2013) using a chlorine-based disinfectant, 10% povidone-iodine, 2% chlorhexidine in 70% alcohol, and 2% chlorhexidine gluconate. In clean and dirty conditions, all but the 2% chlorhexidine gluconate resulted in a >4.5 log reduction in the amount of C. auris present in the suspension. Interestingly, the povidone-iodine was not as effective against C. albicans, achieving only a ~3-log reduction. Also, it is worth noting that the chlorine-based disinfectant was tested with a longer 5 minute contact time, to reflect the use of this product as a surface disinfectant rather than skin or hand antiseptic. It would have been good to see the impact of the chlorine-based disinfectant with a shorter (and more realistic!) contact time; a 5 minute contact time is very difficult to achieve in practice, so this is not realistic of the use of disinfectants in practice.

The 2% chlorhexidine gluconate achieved a 1-3 log reduction on all strains of C. auris, within the 2 minute contact time. The testing methodology is important here: 4% chlorhexidine washcloths were shown to inhibit the growth of C. auris when tested using an experimental methodology in a recent study, which involved placing swatches of the cloths onto culture media to observe whether zones of clearing occurred. This experimental methodology is probably a better model for in-use efficacy, because it accounts for extended exposure to chlorhexidine due to residual activity. Also, it’s important to note that 4% chlorhexidine gluconate was diluted to 2% to match the concentration of chlorhexidine in the 2% chlorhexidine in 70% alcohol suspension.

These findings support the use of a range of disinfectants and antiseptics including chlorine-based disinfectants, and iodine-based and chlorhexidine- based antiseptics in the prevention and control of C. auris.


More single rooms = less MDR Gram-negatives in the ICU

An 11 year Dutch study provides compelling evidence that a move to single rooms from multi-occupancy bays dramatically reduced the burden of multidrug-resistant (MDR) Gram-negative bacteria in the ICU.

The study was centred in a 16 bed ICU in The Netherlands. From 2002-2009, the ICU was composed of a mixture of multi-occupancy bays and single rooms. Then, from 2009-2013 (the end of the study), a new ICU was opened with 100% single rooms. During the period before the move to the new ICU, there were frequent and sustained clusters of clonally related MDR Gram-negative bacteria including Klebsiella, Enterobacter, Serratia, Pseudomonas and Acinetobacter species. After the move to the new ICU, there was a significant reduction in the burden of these bacteria on the ICU, with the total number of MDR Gram-negative bacteria cases falling from around 120 to 20 per 12 month surveillance period.

The authors carefully evaluated the situation to rule out other factors that may have explained this reduction, showing that there were no significant changes in bed occupancy and the number of admissions. However, it is important to note that some important factors that may have explained the reduction could not be measured, for example, compliance with hand hygiene and other basic IPC practices. Also, selective digestive decontamination (SDD) was in use before the more to the new ICU and ceased shortly before the move. Stopping SDD would have reduced the selective pressure for antibiotic resistant bacteria, so could well have contributed to the reduction. Finally, there was no control group to measure the impact of other interventions.

Despite these limitations, this study along with several others, provides evidence that moving to single rooms reduces the transmission of antibiotic resistant bacteria.


Antiseptics and disinfectants to support the prevention and control of Candida auris


Candida auris is an important emerging pathogen, which caused a large outbreak in a London hospital and has been reported from around the world. It shows a high level of resistance to antibiotics and appears to spread rapidly in hospitals. A new study evaluates the efficacy of various antiseptics and disinfectants that could support the prevention and control of C. auris.

The authors evaluates the efficacy of two commonly used disinfectants (chlorine and hydrogen peroxide vapour) and antiseptics (chlorhexidine gluconate and povidone iodine) against 34 Candida species, including 28 C. auris isolates. HPV was tested in the gas phase, whereas two chlorine-based products and the antiseptics (chlorhexidine gluconate and povidone iodine) were tested in the liquid phase, to represent the uses of these disinfectants / antiseptics in practice. Also, a novel methodology was used to test the efficacy of two brands of pre-impregnated 2% chlorhexidine gluconate washcloths (including the Clinell Wash Cloths). These were tested by adding a cut piece of the wash cloths onto the surface of an agar plate and performing measuring the diameter of the zone of clearing.

Gas phase HPV inactivated most of the C. auris isolates tested, and was considered to be 96.6%-100% effective. This suggests that longer HPV exposure may be necessary to fully inactive C. auris. All Candida species were inactivated fully by in-use concentrations of the disinfectants and antiseptics tested. In the experimental procedure to test the antimicrobial activity of the pre-impregnated wash cloths, the C. auris isolates tested appeared to be less susceptible than the non-C. auris isolates tested, suggesting that C. auris is less susceptible to chlorhexidine than non-C. auris isolates, as seems to be the case for most other disinfectants and antiseptics. Both types of pre-impregnated wash cloths performed similarly.

These results suggest that antiseptics such as chlorhexidine gluconate and povidone iodine, and disinfectants such as chlorine and hydrogen peroxide vapour are suitable for preventing the transmission of C. auris, and that current in-use concentrations are adequate.



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