MERS joins the more-environmental-than-you-may-think club


I blogged about a review of the surprising ability of some respiratory viruses (especially SARS-CoV and Influenza virus) to survive on dry surfaces last year. In the review, I predicted that MERS-Cov would also share the same ability to survive on dry surfaces as SARS-CoV – so I was interested to see a recent article in CID demonstrating that MERS is indeed more environmental than you may think.

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Surface contamination and respiratory viruses with pandemic potential (SARS, MERS and influenza): an underestimated reservoir?

Droplet airborne direct and indirect contact figure_final

Most virologists would probably tell you that enveloped viruses are generally pretty fragile outside of their host and so wouldn’t survive for long on dry surfaces. They may well say “If you were talking about a non-enveloped virus (like norovirus) then, yes, it would probably survive on surfaces for quite a while. But enveloped viruses, no – you’d be lucky if it survived for more than a few hours.” But when I looked at the literature to investigate the potential for dry surface-mediated transmission of respiratory viruses with pandemic potential (SARS, MERS and influenza), the picture that emerged was quite different. These respiratory viruses can survive on dry surfaces for ages, and the contaminated environment may well be an underestimated reservoir for their transmission. This is summarised in a review published recently in the Journal of Hospital Infection.

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Biofilms make the hospital environment far from ‘inanimate’


Anybody doubting that biofilms really do exist on dry hospital surfaces needs to read this study: biofilms are there, they are complex, and they are common. A landmark study by the same Australian Vickery group published in 2012 first identified biofilms on a handful of dry hospital surfaces in an ICU. But this study is far more comprehensive and convincing.

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Fidaxomicin reduces C. difficile environmental contamination

It is well-established that fidaxomicin reduces the recurrence rate of C. difficile infection (CDI), but this study from my old research group at GSTT / KCL is the first to evaluate the impact of treatment with fidaxomicin on environmental contamination. The bottom line is that patients treated with fidaxomicin had less C. difficile contamination than patients treated with vancomycin / metronidazole.

In total, the rooms of 38 / 66 (57.6%) patients treated with metronidazole / vancomycin had one or more positive environmental cultures compared with 25 / 68 (36.8%) patients treated with fidaxomicin (P = 0.02). Similarly, when considering all of the sampled environmental sites (four per room), 68 / 264 (25.8%) were positive in patients treated with metronidazole / vancomycin compared with 47 / 272 (17.3%) in patients treated with fidaxomicin (P = 0.02) (see Figure below).

Fidax CDI

Figure: Environmental contamination with C. difficile in the rooms of patients treated with fidaxomicin vs. vancomycin / metronidazole.

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What’s lurking in the hospital environment? The importance of cleaning and disinfection in infection prevention and control


I was asked to speak to a group of link nurses at Southampton Hospital earlier in the week, and thought I’d share my slides, here.

I am passionate about the importance of surface contamination in transmission: I still think it’s really under-rated. I am pretty sure that most healthcare workers would have no idea that your chances of acquiring C. difficile infection (and others) is influenced by who used the room or bed space before you. And who would believe that VRE could survive on a dry surface for 4 years? Or that touching a surface is as important as touching the patient in terms of acquiring contamination on your hands?

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Are beards bug traps? Au contraire!

As the owner of a relatively new beard (see picture below), I was alarmed to hear that my beard is probably as contaminated with faeces as a toilet brush. Fortunately, a Journal of Hospital Infection study from 2014 turns this on its head, showing that those wearing beards are actually less likely to be colonised with staphylococci!

Me and my beard


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The inanimate environment doesn’t contribute to pathogen transmission in the operating room…OR does it?


Nosocomial or hospital-acquired infections are a worldwide problem affecting millions of patients yearly and increasing morbidity and mortality. The role of the hospital inanimate environment (environmental surfaces and surfaces of medical equipment) in the transmission of certain nosocomial pathogens such as C. difficile, norovirus, MRSA, VRE and Acinetobacter is now well established supported by various studies and publications. Most, if not all of these studies, investigated the transmission process in patient rooms or ICUs. Although the role of air in the transmission of pathogens has been extensively studies in the operating room (OR) setting, do contaminated surfaces play a role in pathogen transmission in the OR?

A recent review article published in the journal “Surgical Infection” questioned whether the OR inanimate environment contributed to the transmission of pathogens, hence possibly causing infections including surgical site infections (SSIs). Few studies have investigated surface contamination in the OR and even fewer have investigated possible pathogen transmission from the environment in this setting. While the inanimate environment in the OR has been considered a potential source for pathogens that may cause SSIs for more than 100 years, the role of this environment in the patient acquisition process within this setting is still debatable. Before revealing the conclusions of the review paper, I would like to look at both sides of the argument.


The patient population and length of stay

In a hospital, patients colonised or infected may spend days or even months in ward rooms or ICUs increasing the chance that these patients will contaminate their environment or acquire pathogens from that environment. The likelihood of environmental contamination or pathogen acquisition increases with the length of hospital stay as well as other factors such as gross contamination and soiling.

In the OR setting however most patients spend only few hours under full or partial anaesthesia. This makes it less likely that these patients will contaminate their environment or acquire pathogens from the environment (by self inoculation at least). In addition, although gross contamination via blood for example is common, other type of gross environmental contamination linked to transmission such as diarrhoea and vomiting are less likely to occur in an OR.

The OR environment (surfaces and air)

Unlike most patient rooms, OR air quality is well regulated to prevent contamination via the air. This not only reduces the risk of infection via airborne pathogens but also reduces the amount of pathogens settling on and contaminating environmental surfaces in ORs. In addition, the OR inanimate environment is routinely cleaned/disinfected. Most ORs are cleaned at the end of the working day and many surfaces and areas are cleaned before and between surgeries with strict policies on how to deal with gross contamination (e.g. blood and tissue).

Minimising infection risk

As most SSIs are thought to originate from patients’ or healthcare personnel’s own flora, many interventions are in place in ORs to minimise the risk of contamination and infection. These include policies for hand scrubbing and disinfection, gloving, masks, and the proper preparation of patients’ skin before incision. The instruments used in surgery are also routinely sterilised before surgery to minimise the risk of infection.

Organisms involved in SSIs

The hospital environment has been implicated in the transmission of a number of pathogens including norovirus, C. difficile, MRSA, VRE and Acinetobacter. These pathogens are able to contaminate the environment at a high load and survive for long period of time facilitating transmission and acquisition.  While infections with these organisms can be acquired in the OR, with the exception of Staphylococcus species, these pathogens are not the major causes of SSIs. The environmental resilience of other organisms involved in SSIs is not well characterised and it is unclear whether they can survive long enough in the environment to be transmitted.


The OR environment

ORs are busy, with many personnel involved during a surgical procedure, some of whom come and go in and out of the OR during the process. It is also an environment with multiple and frequent contact between personnel, patients and the environment including medical equipment. It is difficult if not impossible to observe the WHO’s 5 moments for hand hygiene in such an environment, or to clean and disinfect the environmental surfaces effectively during a surgical procedure. Organisms originating from the floor of the OR can also be disturbed by walking and are taken into the air which may increase the risk of infection.

The OR inanimate environment is contaminated

Many people in the general public think of ORs as ultra clean, even sterile, environments. For anyone working in ORs, it is clear that this view is far from the truth. Although modern ORs have strict measures to reduce contamination, the OR inanimate environment becomes contaminated with various organisms including those involved in SSIs. Studies have reported contamination of various OR areas such as anaesthesia equipment, beds, intravenous pumps and poles, computer keyboards, telephones and OR floors.  A variety of pathogens capable of causing infections have been identified including Gram-negative bacilli such as Acinetobacter and Pseudomonas species, Staphylococcus including (MRSA) and Enterococcus. These results may be in part due to the fact that suboptimal cleaning in ORs is a widespread issue in hospitals.

Pathogen transmission occurs in ORs

A number of studies in ORs focusing on the role of anaesthesia equipment and providers in the contamination and transmission of pathogens in ORs have concluded that the hands of anaesthesia providers, patient IV tubing and the immediate patient environment were contaminated immediately before or during patient care with a wide range of bacterial pathogens leading to transmission. Transmission of pathogens from and to the hands of the anaesthesia providers involving the inanimate environment occurs frequently given the frequent contact with the environment in ORs.

Human behaviour in ORs contributes to environmental contamination and transmission

We are all familiar with the view that surgeons tend to be the worst healthcare workers as far as hand hygiene compliance is concerned. However, this is only the tip of the iceberg regarding lapses in infection prevention in ORs. For instance, anaesthesia provider’s behaviour and attitude including confusion on when and how often to perform hand hygiene during a procedure is a common cause of pathogen transmission. In one study, anaesthesia providers touched 1,132 objects during 8 hours of observations in OR, but only performed a total of 13 hand disinfections. No hand disinfections were witnessed at any time during 3 (43%) of the procedures observed. Furthermore, hand hygiene failed to precede or follow procedures, blood exposure or contact with the floor. Alarmingly, it has been reported that objects that fall onto the OR floors during surgery were frequently placed back either on to horizontal work surfaces or even on to the patients themselves during operations.


It is clear that the inanimate environment of the OR, including medical equipment, can become contaminated with pathogens that cause infections including SSIs. These pathogens can then be transmitted to the hands of healthcare workers and have the potential to cause infection. Further studies are necessary to quantify the role of contaminated surfaces in the transmission of pathogens and to inform the most effective environmental interventions in the ORs. Given the serious consequences of SSIs, special attention should be given to the proper cleaning and disinfection of the inanimate environment in ORs in addition to the other established measures to reduce the burden of SSIs. These include addressing the human behaviour that contributes to environmental contamination and transport of surface pathogens into the vulnerable sites of patients during surgery. Such measures include reducing human traffic in ORs, stricter adherence to the standard operating protocols during procedures, and compliance with proper hand hygiene and gloving. Specific hand hygiene guidelines tailored to OR personnel may be needed given the large number of hand contact events per hour in these settings.

Image: NIH Library.

Reflections from HIS 2014, Part II: Dealing with the contaminated environment


Welcome to Part II of my reflections from HIS. For the box-set, see the list at the beginning of Part I here.

Dr Karen Vickery – Multispecies biofilms on dry hospital surfaces – harbouring and protecting multiantibiotic resistant organisms

Probably the most important update from the entire conference was more data from the Vickery lab on biofilms on dry hospital surfaces. She excised 44 dry surface samples from the ICU, put them under the electron microscope and, lo and behold, 41 of them (93%) had fully-fledged (if somewhat unusual) EPS-producing biofilms on! The implications are huge: this could explain extended surface survival, poor success rate of surface sampling, and result in reduced biocide susceptibility up to the tune of 1000x (see my review just published in JHI with Karen as a co-author for more on biocides and biofilm susceptibility).

Dr Silvia Munoz-Price – Controlling multidrug resistant Gram-negative bacilli in your hospital: We can do it so can you!

Dr Munoz-Price described her hospital’s impressive reductions on carbapenem-resistant A. baumannii – from 12 new isolates per week to virtually none today. So what worked? It’s difficult to be sure since it was a bundled intervention. Dr Munoz-Price described the rationale behind some elements of the bundle: environmental surface and staff hand sampling to visualize the invisible, environmental cleaning and disinfection to deal with the ‘fecal [sic] patina’ [a stooly veneer emanating from the rectum] (see Dr Munoz-Price and Dr Rosa’s guest blog for more details), and chlorhexidine bathing. Perhaps the most interesting aspect was the various implementation challenges that were overcome. It was amazing how far removed practice ‘in the trenches’ was from the policy set by the epidemiologist’s office, exemplified by environmental staff buying their own UV lamps to for “spot cleaning” removal of fluorescent markers of cleaning thoroughness. Overcoming these challenges required more that the stick (citations for non-compliance, which failed); culture change takes understanding, time and a very large carrot (and some sticks too, sometimes).

Jim Gauthier – faeces management

A number of key pathogens are associated with faecal colonization and shedding: C. difficile, VRE, ESBL and CRE. Jim didn’t mention MRSA, but this can also cause gastrointestinal colonization and, more controversially, infection. Enterobacteriaceae can survive on dry surfaces for longer than you’d expect, too. We traditionally worry about surface contamination of high-touch sites in inpatient settings. Floor contamination isn’t important (unless you happen to be a wheel chair user, a toddler, or drop your pen). Contamination in outpatient settings isn’t a problem either (unless you happen to have a fairly short consultation for a patient with VRE). So, what to do? Jim introduced the idea of a ‘hierarchy of control’; put another way, prevention is better than cure, so do we have the right systems in place to manage faeces which is teeming with hospital pathogens? For example, should we be enforcing mandatory contact precautions for all contact with faeces (standard precautions – which aren’t very standard anyway – are probably not adequate)? Finally, Jim mentioned the growing importance of faecal microbiota transplantation (and hearing a Canadian speak about this reminded me of a hilarious spoof video).

No-touch automated room decontamination (NTD)

medical equipment in a hospital roomFigure: Hospital bed rails are frequently contaminated, and often not easy to clean and disinfect using conventional methods. 

Paul Dickens – establishing Ebola surge isolation capacity in the UK

Paul Dickens gave a whistle-stop overview of the detailed plans for Ebola surge capacity in the UK (perish the thought). He began by describing the replacement of formaldehyde with hydrogen peroxide vapour for the decontamination of the patient isolators at the Royal Free High Level Isolation Unit (HLIU). They now have a tried and tested process and protocols in place to get the HLIU back online within days using hydrogen peroxide vapour decontamination, where the previous protocol using formaldehyde put it out of action for 6 weeks! (I was involved in writing the protocols for this tricky decontamination assignment, which were reported on a poster published at HIS.) Other challenges in establishing surge capacity include staff expertise, and PPE recommendations, supply & training. Surge capacity is now established. Let’s just hope we won’t need it!

Dr Frédéric Barbut – How to eradicate Clostridium difficile spores from the environment

There’s now plenty of evidence that contaminated surfaces contribute to the transmission of C. difficile. These environmental intervention studies show a 50-80% reduction in the rate of CDI; does this mean that 50-80% of CDI acquisition is environmentally-associated? This seems too high, but it’s difficult to think of another explanation. Furthermore, there is emerging but compelling evidence of a proportional relationship between the degree of C. difficile surface contamination and transmission risk? I really don’t think that the public have yet ‘got’ that the previous occupant can influence acquisition risk. And when they do, I think there will be increasing demand for properly decontamination rooms. So, is it time to turn to NTD systems? Sometimes, yes. And do you go for hydrogen peroxide or UV? Well, that depends on what you’re trying to achieve! If you’re trying to eliminate pathogens, which sometimes you will be, then hydrogen peroxide vapour is the best choice. But if you’re trying to reduce contamination levels without necessarily eliminating all pathogens, then UV is the best choice due to its speed and ease of use.

The debate: “Hospitals that do not use high-tech decontamination of the environment are doing their patients a disservice.”

This debate pitted Profs Hilary Humphreys and Phil Carling (pro) against Peter Hoffman and Martin Kiernan (con). It was lively, entertaining and engaging…

Prof Humphreys argued that it is not acceptable to admit patients to rooms with inherent additional risk for transmission. We can address this by ‘walking like the Egyptians’ and copperising our surfaces, for which there is now some data with a clinical outcome. Another approach is NTD systems, for which data (including some clinical outcomes) are emerging. Prof Carling’s presentation was somewhat unusual, with his arguments seemingly an appeal to common sense rather than drawn from the published literature.

Martin Kiernan began by acknowledging the role of the environment, but that hand contamination is almost always the final vector (and there’s some evidence for this). The cornerstone of Martin’s argument was that whether NTD systems work is the wrong question. We should be focusing our time, money and attention on improving conventional methods which have been shown to reduce transmission. Peter Hoffman complemented Martin’s pragmatic viewpoint with thorough, thoughtful critiques of the studies on HPV decontamination with a clinical outcome. The 2008 Boyce study has more holes than the 2013 Passaretti study, which itself is far from watertight!

The key argument for turning to NTD systems is that admission to a room previously occupied by a patient with an MDRO increases the risk of acquisition due to residual contamination, and NTD decontamination mitigates this increased risk. So, my own conclusion is that hospitals that do not use high-tech decontamination of the environment are indeed doing their patients a disservice. Sometimes!

Look out for the third and final installment of my reflections from HIS 2014 at some point tomorrow!

Image: Medical equipment in a hospital room.

HIS Poster Round: Dealing with contaminated hands, surfaces, water and medical devices

poster round

I was delighted to be asked to lead a poster round at the Healthcare Infection Society (HIS) conference. I was a bit disappointed to see that the poster sessions are tacked on to the end of the day (when everybody’s had enough and really just wants to retreat to their hotel room for an hour before the evening’s activities). My view is that posters are the lifeblood of conferences (and I am not alone in this view); they should have much more prominence, with a “ringfenced” session integrated into the main program.

Anyway, whinge over, I thought I’d share which posters I chose, why I chose them, and what I want to know about them.

You can access the abstracts here.


#3200 Longhurst et al. Hand drying methods in NHS England Trusts, September 2013.

I chose this poster because it’s becoming increasingly clear that the choice of hand drying method can influence the degree of bacterial contamination. Also, whilst I accept the economic and environmental benefits of jet and warm air dryers, they always seem to leave my hands a bit damp. (Perhaps I just have sweaty palms.) Anyway, this is what I want to know about this poster:

  • Why did you feel the need to ‘enforce’ a response by using the Freedom of Information act?
  • Why do you think jet / warm air dryers were rare in clinical areas?
  • Do you think that jet and to a lesser extent warm air dryers result in dangerous dispersal of microbes?

#3349 Tang et al. A 3 year hand hygiene program to increase compliance rate for heatlhcare providers in the A&E Department of Tuen Mun Hospital in Hong Kong.

There’s not a lot of data on hand hygiene compliance in A&E. A 2005 study examined compliance with hand-washing in the TV show ER, reporting a hand hygiene compliance rate of 0.2%. Yep, that’s ZERO POINT TWO PERCENT! Although reality is marginally better (according to this review), there’s work to be done, so I chose this poster mainly because of the impressive impact in improving hand hygiene compliance. My questions are:

  • Which of the barriers to hand hygiene that you mention do you think is most important?
  • Who was on your task-force to decide what to do?
  • How many people completed the questionnaires?
  • How many observations were done in each time period?
  • How do you measure that the awareness of hand hygiene increased?

#3174 Khanafer et al. Hospital management of Clostridium difficile infection: a literature synthesis

This is a novel review of the literature: using the ORION checklist to capture variables that help us to determine what works to control CDI from outbreak reports and intervention studies. Here’s what I want to know:

  • Can we really derive anything useful about which intervention works when you have more than one variable, even if studies are reported in a structured way? (High school science is pretty clear: change one variable at a time!)
  • How can these % reductions be so high when (apparently) only 30% of CDI is hospital-acquired (according to some people’s interpretation of the Oxford WGS difficile study)?
  • Which is the single most important intervention to prevent CDI transmission?


#3285 Cunningham et al. VRE Outbreak Control – the Need for Speed (Use of Molecular Technology)

Two of my favourite subjects: VRE and rapid diagnostics! Here are my questions:

  • Why bother trying to control VRE? Some pretty persuasive voices are arging that it’s not worth it!
  • Are you sure that rapid diagnostics made the difference? You also introduced enhanced cleaning / disinfection, extra screening, pre-emptive isolation, and extra staff and equipment.
  • How do you explain the four clusters?
  • Did you culture in parallel? If so, what was the sensitivity and specifity of the PCR test?

#3312 Whiteley et al. The problem of rapid ATP systems may be scaling using Relative Light Units (RLU)

This poster wins the prize for the most detailed poster in conference history; I think they’ve squeezed enough words in for a full length article. But the findings are important. All ATP bioluminescence systems are not equal: a way to standardize RELATIVE light unit (RLU) output would be extremely useful.

  • What is ‘coeffecient of variance (CoV)’, and what does it mean?
  • Does lower CoV = a better ATP bioluminescence system?
  • Clearly, hand held luminometers will not match HPLC in terms of accuracy, but what should our ‘CoV’ tolerance be?
  • Do you have a way to distinguish variaibilty of sampling (i.e. pickup of ATP on the swab) from variability in ATP detection by the device?
  • Would ATP correlate better with microbial concentration if device variability were removed (e.g. through HPLC analysis)?

#3393 Maynard et al. The use of Pseudalert® for the routine analysis of water samples by engineers

I like technology and I like innovation, so this is right up my steet. Here’s my questions:

  • How does the limit of detection for Pseudalert (1 cfu / 100 mL) compare with conventional culture, in theory?
  • How much training is required to use it?
  • Why 100 mL for Pseudalert, and 500 mL for culture?
  • Is culture the gold standard method? If so, the specificity of Pseudalert in Hospital 1 is terrible!


#3197 Farrugia et al. Reducing methicillin resistant Staphylococcus aureus (MRSA) bacteraemia in haemodialysis patients within a high incidence setting

I chose this poster purely for the dramatic reduction in MRSA bacteraemia in a specialist setting. I would like to know:

  • Is the high initial rate explained by haemodyalisis cathethers being left in for too long?
  • ‘Prevalence of CA-MRSA 8.8%’? What does this mean? 8.8% of healthy individuals carrying CA-MRSA, or 8.8% of hospital MRSA is community-associated clones?
  • Lots of interventions – do you have a feel for which was most important?

#3277 Stenger et al. A hydrogel interpenetrating polymer network in vascular catheters loaded with thioridazine and dicloxacillin facilitates slow surface release and inhibits staphylococcal biofilm formation in vitro and in vivo

I am interested in approaches that replace the traditional use of antibiotics with biocides (which have a much lower risk of promoting bacterial resistance). Whilst this catheter was dosed with an antibiotic, I think the technology could theoretically be dosed with any biocide. Also, I’m fascinated by the application of an anti-psychotic drug in infection control:

  • Please explain the principle of ‘interpenetrating polymer network’ (IPN).
  • Could this same technology be used to dose the catheters with any drug or biocide?
  • Can you modify the rate of release?
  • Who on earth decided to see whether an anti-psychotic drug (thioridazine) has antibacterial properties?

If anybody has any answers to my questions, please fire away!

Image: Andrea Wiggins.

Are contaminated hands more important than contaminated surfaces?

Cast your minds back to the 2010 HIS conference in Liverpool and Drs Stephanie Dancer and Stephan Harbarth debating the relative importance of contaminated hands vs. surfaces in the transmission of MDROs. I don’t remember the details of the debate, but I do remember the surprising lack of evidence on both sides. Back then, we had no real way to quantify the contribution of the environment to the transmission of MDROs, or to measure the relative importance of contaminated hands vs surfaces. The evidence has evolved to the extent that a group of US researchers have published a paper modeling the relative contribution of contaminated hands vs surfaces to the transmission of MDROs. I like the paper very much, and the authors should be congratulated for breaking new ground in understanding transmission routes of MDROs.

The model simulates patient-to-patient transmission in a 20-bed ICU. The values of the parameters that were used to build the model were sensible on the whole, although baseline hand hygiene compliance was set at 57-85% (depending on staff type and whether at room entry or exit), which seems rather generous when baseline environmental cleaning compliance was set at 40%. Also, the increased risk from the prior room occupant for MRSA and VRE was set at 1.4 (odds ratio) for both, whereas it probably should be higher for VRE (at least >2) based on a number of studies.

100 simulations were run for each pathogen, evaluating the impact of step-wise changes in hand hygiene or terminal cleaning compliance. The key finding is that improvements in hand hygiene compliance are more or less twice as effective in preventing the transmission of MDR A. baumannii, MRSA or VRE, i.e. a 20% improvement in terminal cleaning is required to ‘match’ a 10% improvement in hand hygiene compliance. Also, the relationship between improved terminal cleaning and transmission is more or less linear, whereas the relationship with hand hygiene shows relatively more impact from lower levels of hand hygiene compliance (see Figure, below). Thus, the line for improving hand hygiene or terminal cleaning would intercept and indeed cross over at around 40 or 50% improvement. The implication here is that hand hygiene is more important at low levels of compliance, whereas terminal cleaning is more important at high levels of compliance (although don’t forget the difference in the baseline compliance ‘setpoint’.

hand v env Figure. The impact of percentage improvement in hand hygiene or terminal cleaning on the transmission of MDROs. Dotted line represents my not-very-scientific extrapolation from eyeballing the data.

The study raises some important issues for discussion:

  • It had not struck me before that the level of compliance with hand hygiene and environmental cleaning are nearly identical, on average, with only around 40% of hand hygiene opportunities met and 40% of environmental surfaces cleaned if human beings are left to their own devices. Both of these figures can be improved considerably with concerted effort, but the sustainability of these improvements without continued effort is rather disappointing.
  • The models address MRSA, VRE and MDR A. baumannii transmission. It’s a little strange that C. difficile was not included, since most consider this to be the ‘most environmental’ hospital pathogen.
  • The study only modeled the impact of terminal cleaning, whereas daily cleaning seems likely to also be an important factor (which is acknowledged as a limitation in the discussion). This seems especially important in light of data that touching a contaminated surface carries approximately the same risk of hand contamination as touching an infected or colonized patient.
  • I am not certain that this assumption makes logical sense: ‘thoroughness of cleaning of 40% implies that, given a single cleaning opportunity, there is a 40% probability that the room will be cleaned sufficiently well to remove all additional risk for the next admitted patient’. This would be true if cleaning was performed to perfection 4 times out of 10, whereas it is actually performed with 40% efficacy 10 times out of ten! To this end, it would be interesting to insert the various automated room disinfection systems into the model to evaluate and compare their impact. Indeed, hydrogen peroxide vapour has been shown to mitigate and perhaps even reverse the increased risk from the prior room occupant (for VRE at least).
  • In the introduction, the authors comment that ‘A randomized trial comparing improvements in hand hygiene and environmental cleaning would be unethical and infeasible.’ I see what they’re saying here, in that it would be unethical by modern standards to investigate the impact of no hand hygiene or no environmental cleaning (although this has been done for hand hygiene), but it would be useful, feasible and ethical to perform a cluster RCT of improving hand hygiene and environmental cleaning. It would look something like the classic Hayden et al VRE study, but with an RCT design.
  • How useful is mathematical modeling in informing decisions about infection prevention and control practices? This is not the first mathematical model to consider the role of the environment. For example, researchers have used models to evaluate the relative importance of various transmission routes including fomites for influenza. But a model is only as good as the accuracy of its parameters.
  • Does this study help us to decide whether to invest in increasing hand hygiene or terminal cleaning? To an extent yes. If you have awful compliance with both hand hygiene and terminal cleaning at your facility, this study suggests that improving hand hygiene compliance will yield more improvement than improving terminal cleaning (for A. baumannii, MRSA and VRE at least). However, if you have high levels of compliance with hand hygiene and terminal cleaning, then improving terminal cleaning will yield more.

In general, this study adds more evidence to the status quo that hand hygiene is the single most effective intervention in preventing the transmission of HCAI. However, in a sense, the hands of healthcare workers can be seen as high mobile surfaces that are often contaminated with MDROs and rarely disinfected when they should be!

Article citation: Barnes SL, Morgan DJ, Harris AD, Carling PC, Thom KA. Preventing the transmission of multidrug-resistant organisms: modeling the relative importance of hand hygiene and environmental cleaning interventions. Infect Control Hosp Epidemiol 2014; 35: 1156-1162.