The hospital environment in healthcare-associated infections – an interview with Stephanie Dancer

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What role might the healthcare environment play in infections? And how could this be mitigated? We speak to Stephanie Dancer, Consultant Microbiologist in NHS Lanarkshire and Professor of Microbiology at Edinburgh Napier University (both UK), about the healthcare environment and its role in healthcare-associated infections (HAI). In addition, she gives her thoughts on hospital cleaning and how we can measure cleanliness in order to prevent HAI.

Does the healthcare environment play a role in healthcare-associated infections (HAI)?

This image is a diagram showing the potential pathways of pathogen transmission

Pathways of pathogen transmission [6]

There is no doubt that the healthcare environment plays a major role in healthcare-associated infections (HAI) [1].  Pathogens responsible for HAI are characterized by their survival properties, which allow them to persist on surfaces for days if not weeks [2].  These surfaces provide a repository from which they may be transmitted to patients, directly or indirectly. Transmission pathways are facilitated by hands, air currents or surface contact, with increased risk of HAI following cleaning/decontamination deficits [3]. The best evidence that we have for the role of the healthcare environment may be surmised from the increased HAI risk faced by a patient admitted into a room previously occupied by a patient with the same HAI [4]. This risk remains despite so called terminal cleaning. It also challenges the priority afforded hand hygiene and indeed, any other infection prevention activities on the ward or unit in which the room is located.

Which sites pose the highest risk for HAI?

Healthcare-associated pathogens can be found on any surface in a hospital including hard and soft furnishings, beds, linen, bathroom items, equipment and even in the air. Sites that are frequently handled are more likely to host pathogens, as are those that escape regular cleaning attention [5]. Contaminated hand-touch sites facilitate transmission between the hands of staff, patients or visitors and other sites including environmental surfaces, equipment and patient sites [6]. The risk is enhanced when surfaces located beside the patient are contaminated or infrequently cleaned. Environmental sampling suggests that the bed frame, bedside table and locker; nurse call button, bed control and light switch are prime sites for pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococci (VRE) [7]. Locating an established healthcare pathogen on a hand-touch surface is associated with finding high levels of aerobic colony forming counts from the same surface [8].

How should we clean the healthcare environment?

This image shows someone Cleaning a door handle

Cleaning a door handle

Any clinical area accommodating patients should receive daily cleaning attention, with cleaners working to a specified protocol. Some areas, e.g. operating theatres, critical care, transplant and special care baby units, require higher cleaning frequencies. The protocol should prioritize hand-touch sites within the bed space and broadly follow the ‘one wipe; one site; one direction’ method [9]. The whole point of cleaning, as defined, rests on the removal of surface soil for safety, prevention, aesthetic and functional purposes [10]. Removing dirt is assumed to remove any pathogens that may be associated with surface soil. Clinical equipment deserves its own cleaning schedule and this should be performed before and after patient use [11]. Use of cleaning products is determined by individual hospitals or healthcare regions, with choices between detergents or disinfectant based products, both of which confer their own advantages and disadvantages [12]. While detergents are much less likely to affect the environmental microbiome compared with disinfectants, cleaning with either could disrupt surface biofilm to release long lost pathogens capable of causing HAI [13]. Complete obliteration of surface microbes with powerful disinfectants encourages proliferation of organisms able to tolerate the agents used [14]. These organisms may be pathogens and they are likely to be multiply resistant to antibiotics, especially if repeatedly exposed to disinfectants [15].

How do we measure surface cleanliness in a hospital?

Dipslides coated in elemental agar showing quantitative aerobic colony counts [16]

Given the importance of healthcare environments, there is a clear need to be able to measure surface level cleanliness in order to provide assurance for staff and patients that their hospitals are safe [16]. Measuring cleanliness will also help toward evaluating cleaning systems or products. Cleanliness can be measured by standardized microbiological sampling, using both qualitative and quantitative parameters. An alternative monitoring system uses ATP, measured by detected luminescence from organic soil constituents after sampling. Both of these methods allow collection of tangible values, which can be evaluated according to a range of available standards [17]. A sudden increase in values may provide an early warning of cleaning deficits or even herald an outbreak.

It is also possible to measure the cleaning process itself rather than surface bioburden after the cleaner has left. This can be done by prior marking of target sites using invisible fluorescent markers. [18] Supervisors can then check for removal of the marker with a UV light source and monitor the percentage of sites where the marker has been removed. The results can be fed back to the cleaning workforce and the process supported by an educational package for all staff.

Is there a relationship between surface bioburden and HAI risk in the healthcare environment?

Relationship between quantity of microbial soil around an ITU bed and rate of acquired staphylococcal infections on 10 sampling days [20]

Since it is widely accepted that contaminated surfaces constitute an infection risk in the healthcare environment, it follows that higher surface bioburden might increase the HAI risk [19]. Quantitative microbiological sampling of hand-touch sites can be compared against HAI rates in order to examine a possible relationship [3]. While these types of studies have not yet been extensively performed, there have been attempts at modelling bioburden against HAI rates including those of specific pathogens [20]. Current evidence suggests that there is indeed a relationship between near-patient microbial soil and HAI risk. Conversely, eliminating surface bioburden through cleaning initiatives or coating sites with antimicrobial paint or heavy metals may also decrease HAI rates [3].

  1. Dancer SJ. The role of environmental cleaning in the control of hospital-acquired infection. Infect. 73, 378–85 (2009).
  2. Kramer A, Schwebke I, Kampf G. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect. Dis. 6, 130 (2006).
  3. Dancer SJ. Controlling hospital-acquired infection: focus on the role of the environment and new technologies for decontamination. Microbiol. Rev. 27(4), 665–90 (2014).
  4. Mitchell BG, Dancer SJ, Anderson M, Dehn E. Risk of organism acquisition from prior room occupants: a systematic review and meta-analysis. Hosp. Infect. 91(3), 211–7 (2015).
  5. Smith SJ, Young V, Robertson C, Dancer SJ. Where do hands go? An audit of sequential hand-touch events on a hospital ward. Hosp. Infect. 80, 206–11 (2012).
  6. Dancer SJ, Adams CE, Smith J, Pichon B, Kearns A, Morrison D. Tracking Staphylococcus aureus in the intensive care unit using whole-genome sequencing. Hosp. Infect. 103, 13–20 (2019).
  7. Dancer SJ. Importance of the environment in MRSA acquisition: the case for hospital cleaning. Lancet Infect. Dis. 8, 101–13 (2008).
  8. Dancer SJ, White L, Robertson C. Monitoring environmental cleanliness on two surgical wards. J. Environ. Health Research. 18, 357–64 (2008).
  9. Sattar SA, Maillard J-Y. The crucial role of wiping in decontamination of high-touch environmental surfaces: review of current status and directions for the future. J. Infect. Control. 41, S97–104 (2013).
  10. Dancer SJ. Mopping up hospital infection. Hosp. Infect. 43, 85–100 (1999).
  11. Anderson RE, Young V, Stewart M, Robertson C, Dancer SJ. Cleanliness audit of clinical surfaces and equipment: who cleans what? Hosp. Infect. 78(3), 178–81 (2011).
  12. Dancer SJ. Do’s and don’ts for hospital cleaning. Opin. Infect. Dis. 29(4), 415–23 (2016).
  13. Bogusz A, Stewart M, Hunter J, Yip B, Reid D, Robertson C, et al. How quickly do hospital surfaces become contaminated after detergent cleaning? Healthcare Infect. 18, 3–9 (2009).
  14. Sattar S. Promises and pitfalls of recent advances in chemical means of preventing the spread of nosocomial infections by environmental surfaces. J. Infect. Control. 38, S34–40 (2010).
  15. Kampf G. Challenging biocide tolerance with antiseptic stewardship Hosp. Infect. 100, e37–39 (2018).
  16. Dancer SJ. How do we assess hospital cleaning? A proposal for microbiological standards for surface hygiene in hospitals. Hosp. Infect. 56(1), 10–5 (2004).
  17. Mulvey D, Redding P, Robertson C, Woodall C, Kingsmore P, Bedwell D, Dancer SJ. Finding a benchmark for monitoring hospital cleanliness. Hosp. Infect. 77(1), 25–30 (2011).
  18. Carling, PC, Briggs, JL, Perkins, J, Highlander, D. Improved cleaning of patient rooms using a new targeting method. Infect. Dis. 42, 385–8 (2006).
  19. White LF, Dancer SJ, Robertson C, McDonald J. Are hygiene standards useful in assessing infection risk? J. Infect. Control. 36(5), 381–4 (2008).
  20. Smith J, Adams CE, King MF, Noakes CJ, Robertson C, Dancer SJ. Is there an association between airborne and surface microbes in the critical care environment? Hosp. Infect. 100(3), e123–e129 (2018).

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