Wiping little and often to keep MRSA at bay

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A new study in BMC Infectious Diseases models the impact of various cleaning strategies on the transmission of MRSA. Regular wiping of high touch surfaces was more effective than daily cleaning of the whole room in preventing the transmission of MRSA.

The study team created a simple mathematical model to explore the transmission of MRSA. And herein lies the main limitation: "all models are wrong, but some are useful"! The real challenge with modelling studies is whether we really know enough to accurately 'parameterise' the model. Also, even when there is data for a given variable (e.g. the amount of MRSA that is shed by a patient into the environment), this will vary greatly (e.g. where the patient is infected or colonised, strain of MRSA, how mobile the patient is, and environmental factors such as airflow, and others). Models like this have to come up with mathematical ways to model all of these uncertainties. So, you can see why some people think that mathematical models are not really that useful. However, they allow us to explore transmission pathways in a way that would be extremely challenging to do, and sometimes not possible to do, using experimental studies.

The study evaluated the transmission of MRSA from one patient to another who were in adjacent hospital rooms. The key variables were the type of cleaning (either irregular cleaning of the whole room), or wiping of touch points (variable frequency of cleaning high and low touch points). The main finding was that regular cleaning of touch points in the room was much more effective than once daily cleaning of the entire room. The effectiveness of wiping touch points in preventing transmission increased with the frequency of wiping, perhaps unsurprisingly!

Further work is required to confirm this observation (this is a modelling study after all), but this idea could change the way that we approach hospital cleaning and disinfection. Could we start talking in terms of the "Five Moments for Environmental Hygiene" to mirror the "Five Moments for Hand Hygiene"? Should healthcare workers disinfect each surface that they touch? Or perhaps the same wipe should be used to disinfect both hands and surfaces following each of the Five Moments for Hygiene?! Just thoughts at this stage, but this study certainly does make you think!

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Caps off to chlorhexidine for needleless connector disinfection

A number of options are available for preventing the introduction of microbes into central venous access devices (CVAD) via needleless connectors, including disinfection using alcohol or chlorhexidine, or disinfectant impregnated caps. A recent ICHE study compared three different needleless connectors, and three different decontamination approaches (alcohol scrubbing, chlorhexidine-alcohol scrubbing, and an alcohol-impregnated cap). Chlorhexidine scrubbing was by far the most effective method: so it's caps off to chlorhexidine for needleless connector disinfection!

The laboratory study tested a range of bacteria and fungi (Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, and Candida albicans) in three of the most common needleless connectors with or without the presence of human serum. Connectors were inoculated with a clinically-relevant amount of micro-organism, which was allowed to dry. Then, connectors were disinfected using three different methods:
- Scrubbed with 70% isopropyl alcohol (IPA) swabs for 5, 15, or 30s;
- Scrubbed with 2% chlorhexidine gluconate + 70% isopropanol swabs for 5, 15, or 30s; or
- Covered with 70% isopropyl alcohol-impregnated caps for 5 minutes.

The results show clearly that chlorhexidine + 70% alcohol was superior to the other two methods, both with and without the presence of human serum (see chart below). A 5s scrub with chlorhexidine was superior to a 30s scrub with IPA or the caps. Although the effectiveness of all methods was reduced in the presence of human serum, chlorhexidine continued to outperform the other methods.


Chart: Proportion of organisms remaining following disinfection of the needleless connector.


IPA, 70% isopropyl alcohol with 5-, 15-, or 30-second decontamination; CHG, chlorhexidine gluconate in 70% isopropyl alcohol with 5-, 15-, or 30-second decontamination; IC, 70% isopropyl alcohol impregnated cap. * P=<0.05. (Click the image to enlarge)

The study also reports some data on the cost implications of these findings. The chlorhexidine swabs cost around 5p compared with 1p for the IPA swabs, and 15p for the antimicrobial-impregnated cap. Whilst volume would be high given how much needleless connection disinfection goes on in hospitals, the total cost of switching to chlorhexidine swabs from IPA swabs would be pennies compared with the cost of a single CLABSi, which can cost tens of thousands.

This important study establishes firmly that a 5s scrub with IPA is not the way to go for disinfecting needleless connectors, despite this being standard practice in some hospitals. It also shows that active scrubbing is better than passive disinfection: we need to "scrub the hub"! A 15 or 30s scrub with chlorhexidine was markedly more effective than 5s. Although chlorhexidine swabs are more expensive than IPA swabs, the switch will be cost effective even if a single CLABSI is prevented.

Although this is a laboratory study, and may not be representative of the contamination challenge faced in the real world, the authors did their best to make the study representative of the clinical setting; they did this by using a range of organisms at a clinically relevant inoculum, and testing with or without the presence of human serum (to simulate contamination of the needleless connector with blood products). Chlorhexidine disinfection of needleless connectors seems to be the way forward, and it's good to see the recommendation in the EPIC3 guidelines for at least 15s scrub with chlorhexidine plus alcohol for disinfecting needleless connectors!

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