A US study has found that Candida auris exhibited a similar level of susceptibility to UV light as Clostridium difficile spores, and was considerably less susceptible than MRSA. These findings suggest that either extended exposure UV cycles or hydrogen peroxide based room disinfection are required to address environmental contamination with Candida auris.
We have posted before on the efficacy of various disinfectants against Candida auris, supporting that chlorine-based disinfectants and chlorhexidine have a role to play in preventing the transmission of Candida species. This latest laboratory study tested the efficacy of a UV room decontamination system against various species of Candida auris and Candida albicans, MRSA, and C. difficile spores. Metal discs with these organisms dried onto them were placed 5 feet from the device at a height of 4 feet with exposure times of 10, 20, or 30 minutes. UV achieved a <2-log reduction on C. auris after 10 minutes of exposure (vs. a >6-log reduction for MRSA), a 4-log reduction after 20 minutes, and a 6-log reduction after 30 minutes. The efficacy profile of UV against C. difficile and C. auris was similar.
This study is in line with the findings of others that C. auris is able to less susceptible to disinfection than other agents. Therefore, extended exposure UV cycles or hydrogen peroxide based room disinfection should be used to tackle environmental contamination with C. auris.
An impressive randomised multi-centre study in Japan has evaluated the efficacy of 0.5 and 1% alcohol/chlorhexidine with 10% povidone-iodine in preventing colonisation of vascular catheters. The study concluded that chlorhexidine at either concentration is superior to povidone-iodine in preventing the colonisation of vascular catheters.
The study was performed in 16 Japanese intensive care units. The 796 central venous or arterial catheters included in the final analysis were randomised to 0.5% and 1% alcohol/chlorhexidine with 10% povidone-iodine during insertion and dressing changes. Catheter-tip colonisation was 3.7 events per 1000 catheter-days in the 0.5% chlorhexidine group, 3.8 in the 1% chlorhexidine group, and 10.5 in the povidone-iodine group. The rate of catheter-tip colonisation was statistically significantly lower in both chlorhexidine groups compared with the povidone-iodine group.
It’s important to note a couple of limitations in this study. Firstly, the authors compared chlorhexidine in alcohol with a povidone-iodine solution. So it isn’t possible to disentangle the effect of alcohol from chlorhexidine using this design. Secondly, although the authors tested two concentrations of chlorhexidine (0.5% and 1%), both are lower than would usually be used in clinical settings in most parts of the world (2%). Thirdly, there was no impact on the rate of catheter-related bloodstream infections between the two groups, although this may be a factor of sample size, because the primary outcome, for which the study was powered, was catheter tip colonisation.
Despite these limitations, the findings of this large randomised trial are compelling, finding that vascular line-tip colonisation is less than half as likely when chlorhexidine is used during insertion and ongoing line care compared with povidone-iodine. This reinforces that chlorhexidine is a better choice than povidone-iodine for skin decontamination during line insertion and ongoing line care in the ICU setting.
A fascinating new study in AJIC suggests that adding a disinfectant to the toilet bowl before flushing results in a significant reduction in viral contamination of a bathroom. Does this mean we should disinfect the loo before flushing it?
The study used MS2 coliphage as a proxy marker of pathogenic virus contamination. The degree of surface contamination of the bathroom was assessed with and without adding the phage to the toilet bowl (at a high concentration of 10^12) before flushing. The bathroom was heavily contaminated with the phage when it was added to the toilet bowl; surfaces were contaminated up to a concentration of 10^6 per 100cm2. Then, the experiments were repeated but this time disinfectants were added to the bowl before flushing: 5-10% hypochlorite, 0.5-2% hydrogen peroxide, QAC, or 0.23% peracetic acid. Perhaps surprisingly, the hypochlorite had limited impact on the concentration of phage in the toilet bowl until a contact time of 30 minutes, whereas both QAC and peracetic acid resulted in a ~2-log reduction with only a 1 minute contact time. The hydrogen peroxide made a limited impact on the concentration of phage at any concentration or contact time.
So does this mean we should disinfect the toilet bowl before flushing? The major problem with this is that the toilet bowl will be full of bodily fluids and organic matter (well, it’s what the toilet is for), so there’s a big risk that any attempt to disinfect the toilet bowl immediately before flushing are unlikely to reduce contamination of the bathroom. The author did attempt to simulate waste in the bowl using a microbiological culture broth – but I suspect the real thing would be a tougher challenge! However, this study does illustrate the risk of contaminating the bathroom with viral aerosol through toilet flushing, and argues for regular (perhaps more regular) disinfection of the toilet bowl!
2017 has been quite a year. We’d like to take the opportunity to thank all of our customers, suppliers, and readers for your contributions, and to highlight a few of our favorite posts this year.
We hope that you have enjoyed reading our blog as much as we’ve enjoyed writing it. Here’s to a restful Christmas and a happy 2018!
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.
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.
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.
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.
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.