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Infection risks and the environment

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The healthcare environment continues to present a risk of infection transmission, so what can we do to protect patients in a post-pandemic era? The Central Sterilising Club’s 60th anniversary annual scientific meeting showcased the latest evidence for best practice, highlighting some of the potential threats that need to be addressed.

Environmental decontamination was high on the agenda at the Central Sterilising Club’s annual scientific meeting – the pandemic has intensified interest in technologies that tackle airborne pathogens, but the familiar foes of Methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile (C.difficile) and vancomycin-resistant enterococci (VRE) (to name just a few) still remain a challenge. While technologies such as hydrogen peroxide vapour (HPV) and ultraviolet (UV) have an important role in helping to prevent healthcare-associated infections, cleaning is still fundamental to ensure patient safety and to reduce the risk of environmental transmission. But do we give this the training or recognition it deserves?  

Dr. Mark Garvey, consultant clinical scientist in microbiology and deputy director of infection prevention and control at University Hospitals Birmingham NHS Foundation Trust (UHB), tackled this issue in a presentation on ‘Wiping out Infections’

“In healthcare, we are undertaking increasingly complicated work, especially at the University Hospitals Birmingham, one of the largest hospitals in the UK – with over 2,500 beds. We perform transplants every day and put lots of devices into patients, which can provide potential routes into patients for microorganisms,” he commented.  

Eliminating these microorganisms in the environment is key to patient safety. Garvey highlighted a Ted Talk by Jack Gilbert on “The microbiome revolution: why microbes control your life”1 which highlights just how many microorganisms we expel into the environment at any one time. Gilbert points out that around 100 trillion cells in your body are bacterial and only 10 trillion are human – which means you are “outnumbered 10:1 by microbial cells”.

Presenting some worrying examples of infection risks in healthcare settings, Garvey commented that it is easy to see how the environment can play an important role in the transmission of microorganisms. Some of the photos presented during his talk showed evidence of visible faecal matter in healthcare settings, underscoring the importance of environmental cleaning

He explained that pathogens can survive for long periods in the environment – for example, S. aureus (including MRSA) can last from 7 days to >12 months; Enterococcus spp. (including VRE) for 5 days to >48 months; C.difficile (spore form) for >5 months; and Acinetobacter spp. for 3 days to 11 months (Dancer et al, 2014).2 Garvey added that some microorganisms can also survive in ‘protective’ biofilms in the environment making them even more challenging. 

Various studies have looked at organism transfer in clinical environments. One study, by Oelberg et al (2000),3 involved the inoculation of non-infectious cauliflower mosaic virus DNA into a phone in a neonatal unit ICU cubical. The virus spread to 58% of ward sampling sites within seven days of inoculation – spreading to all five other cubicles, contaminating the doorhandles first. 

A paper by Otter et al (2013)4 highlighted an increased risk of acquiring  an infection from the prior room occupant (as high as 71%, if the prior patient had A. baumannii). In addition, a prospective cohort study in an ICU, by Nseir et al (2011),5 also found that successive occupiers of a room are at risk from organisms from previous occupants. Quality audits showed that 56% of rooms were not cleaned correctly – failures were highest for door handles (45%), monitor screens (27%) and bedside tables (16%). 

Cleaning is vital and yet it is either carried out by low paid staff of low status who have been trained, or well-paid staff of higher status, who have not been trained. 

Garvey pointed out that a longer clean is not necessarily a more effective clean, while systems to monitor cleaning are often ineffective or absent.

“When healthcare practitioners undertake their degrees, how much training do they have around cleaning and its importance – particularly around the science and the reasons why we do what we do?” he commented. “Cleaning is a science and we’re trying to get people’s attention. But how much do we teach people on the fundamentals?”

When there are outbreaks, there is a tendency to shift the responsibility onto facilities and, in general, there is confusion over the division of labour. 

To tackle this confusion, a schematic of the categories of cleaning has been developed at University Hospitals Birmingham – from green, amber and red cleans, through to platinum and violet cleans – depending on the infectious status and pathogens involved.

Green cleans, for example, are performed by clinical/ward staff using Clinell wipes, following the discharge of patients (with no known infection and no diarrhoea); platinum cleans are carried out by facilities, following the discharge of patients with Carbapenemase Producing Enterobacteriaceae (CPE) or multi-drug resistant Acinetobacter, and involve a steam clean, Chlor-cleaning, HPV misting and curtain change. Violet cleans are also  performed by facilities and involve Chlorcleaning and curtain changes but use a UV-machine in areas where HPV cannot be used. Pre-cleaning, prior to amber, red, platimum and violet cleans, is performed by the clinical/ward staff.

Garvey commented that, over recent years, wipes have become firmly established in clinical areas in the UK and other countries. They are used on patients, equipment (from nasendoscopes to commodes), and the environment for cleaning and/or disinfection. The advantages are they are convenient and can be placed at the point of care and they are pre-mixed and pre-measured. 

Birmingham previously used a two-stage wipe and instructed nursing staff to use the detergent clean, followed by the disinfection clean.

“When we actually went on to the wards and looked at this, most people would just use the disinfection wipe as the alcohol smelt more potent. However, this fixes things to the surface,” Garvey explained. “Often, staff were not using the detergent wipe. So, we moved to the single-stage Clinell wipes, which contain a surfactant that is good for cleaning. They also contain a disinfectant. When we moved to the one-wipe system, we saw a significant reduction in MRSA acquisition.” (Garvey et al, 2018)6 This was due to the fact that the system made cleaning much easier for staff.

Garvey explained that funding was obtained to take samples to identify microorganisms with the Medical Assessment Unit (MAU) and to examine the cleaning protocols. Environmental samples were taken by swabbing seven high-touch sites, such as the bed rail, patient armchair, patient chair seat, patient table (overside and underside), patient locker and nurse call button. The study looked at the total viable counts before and after cleans. The key take-home message was that the actual physical (green) clean, using Clinell wipes, achieved a significant log reduction in microorganisms in the environment, when performed properly. However, green cleans were often missed.

“The first clean is vitally important. HPV and UV won’t work unless you do a good physical clean in the first instance,” he commented. He explained that the study initially found C.difficile in the MAU environment; after the green clean, it could no longer be found. Garvey suggested that this was due to the physical removal of the spores. However, an important aspect was also the education provided – when education stopped, C.difficile increased; when it was re-started, it went back down.

Garvey went on to highlight an analysis of a randomised controlled trial (RCT) by Anderson et al (2017)7 which assessed four different strategies for terminal room disinfection. The study found that enhanced terminal room cleaning with UV in high-risk rooms led to a decrease in hospital-wide incidence of C.difficile and VRE.

“UV is very effective and is very quick as well,” Garvey commented, adding that it won’t be effective if the room is cluttered with lots of equipment, however, as this will create shadows

University Hospitals Birmingham sought to tackle VRE on its ITU and liver wards, following some outbreaks, which prompted the purchase of a UV machine. Since the introduction, levels have plummeted. 

He went on to highlight a paper, which looked at Pseudomonas aeruginosa infection in augmented care areas, in four large UK hospitals (Halstead et al, 2021).8

Over a 16-week period, all water outlets in augmented care units of four hospitals were sampled for Pseudomonas aeruginosa (P. aeruginosa) and clinical isolates were collected. The outlet and clinical isolates underwent whole-genome sequencing (WGS)

Outlets were positive in each hospital and there were 51 persistently positive outlets in total. WGS identified likely transmission from outlets to patients in three hospitals for P. aeruginosa positive patients. Approximately 5% of patients in the study ‘definitely’ acquired their P. aeruginosa from their water outlets in the intensive care unit. Extensive evidence of transmission was found from the outlet to the patients particularly in the newest hospital, which had the highest rate of positive outlets.

The overall findings suggest that water outlets are the most likely source of P. aeruginosa nosocomial infections in some settings, and that widespread introduction of control measures would have a substantial impact on infections. 

Garvey showed a photo of a sink with paper towels on the floor, surrounding the area, to demonstrate just how far water is dispersed in the room, as well as an image of a water droplet on impact – highlighting the potential spread and trajectory of waterborne pathogens in aerosols. 

Garvey went on to explain how can we tackle the risk of Pseudomonas aeruginosa, from an engineering perspective, highlighting a paper co-authored with Christina Bradley, among others, which looked at possible interventions on a critical care unit. 

Water sampling undertaken on the ICU indicated 30% of the outlets were positive for P. aeruginosa at any one time. Molecular typing of patient and water isolates via Pulsed Field Gel Electrophoresis suggested there was a 30% transmission rate of P. aeruginosa from the water to patients on the ICU.

From February 2014, QEHB implemented engineering interventions, consisting of new tap outlets and PALL point-of-use filters; as well as holistic measures, from February 2016, including a revised tap cleaning method and appropriate disposal of patient wastewater. Breakpoint models indicated the engineering and holistic interventions resulted in a significant (p<0.001) 50% reduction in the number of P. aeruginosa clinical patient isolates over a year.9 Garvey pointed out that appropriate management of water, including both holistic and engineering interventions, is needed to stop transmission of P. aeruginosa from water to patients. The disposal of patient wastewater, cleaning of tap outlets, and cleaning of medical equipment all need to be considered, along with engineering solutions.

“We had three patients who had central line infections involving P. aeruginosa. When we looked at this, they all had the same type. The tap in the IV prep room did not have a Pall filter and the infusion therapy procedure trays were being washed in the water… This shows the importance of teaching staff about cleaning,” Garvey explained.10

Garvey further highlighted new guidelines on automated room decontamination published by a Healthcare Infection Society Working Party.11 The document states that “good practice” includes:

  • Manual cleaning should be completed to the same high standard regardless of the subsequent use of automated cleaning devices.
  • On first use of a fumigant or ultraviolet light in a specific room design, efficacy of sealing should be monitored to ensure safety.
  •  Prioritise different cleaning systems to the type of infection of the most recent room occupant by use of a red/ amber/green rating based on local nosocomial infection rates.
  •  Remove foam materials from the room if fumigant is used unless sealed under an impervious cover.
  • Before purchasing or renting a system, run a mock decontamination cycle in a hospital room to determine turn-around times.
  • After purchasing an ultraviolet-light decontamination system, consider the impact on surface finishes such as whitened polyvinyl chloride (PVC) before purchasing other equipment, and ask the equipment supplier to confirm compatibility.
  • Monitor levels of fumigant or ultraviolet light at regular intervals during the contract to ensure efficacy.
  • When adopting a new automated system or disinfecting a new room design, conduct microbiological culture tests (if permitted in the hospital) or take in-use environmental swab tests before and after disinfection to confirm efficacy. 

Ultimately, he argued that cleaning is a science, and it is time to recognise it as such. We need to change the language – instead of saying “has that been cleaned?”, we should say “is that room/piece of equipment safe?” Garvey stated that nursing staff need to be educated in the importance of cleaning, while solutions need to be simple – such as changing over to more practical wipes. New technologies, such as UV, can help, as the latter is quick and can help hospital flow, but we also need to consider human factors. 

“You need to ask yourself, would you have your mum or loved one go into that room? This is how I broach my outbreak meetings,” he concluded.

At the end of his presentation, Garvey announced that a new PhD has been launched in Christina Bradley’s memory, sponsored by Gamma. Tina was a committee member of the CSC in various positions culminating in being Chair between 2014-17 and was awarded Honorary Life Membership for her significant contributions to the organisation. Her work was well known to the healthcare community, and she provided an enormous contribution to improving overall standards in all areas of decontamination practice. 

Dr. Mark Garvey

Mark Garvey is a consultant clinical scientist in microbiology and the deputy director of infection prevention and control for the Infection Prevention and Control Service at University Hospitals Birmingham NHS Foundation Trust. Mark is also the director of the Hospital Infection Research Laboratory that investigates hospital infection and provides practical. Mark’s interests include water microbiology focusing on Pseudomonas aeruginosa and Mycobacterium chimaera.


1. Gilbert, J, The microbiome revolution: why microbes control your life, Ted Talks, Accessed at: https://
2. ancer SJ. Controlling hospital-acquired infection: focus on the role of the environment and new technologies for decontamination. Clin Microbiol Rev. 2014 Oct;27(4):665-90. doi: 10.1128/ CMR.00020-14. PMID: 25278571; PMCID: PMC4187643.
3. Oelberg DG, Joyner SE, Jiang X, Laborde D, Islam MP, Pickering LK. Detection of pathogen transmission in neonatal nurseries using DNA markers as surrogate indicators. Pediatrics. 2000 Feb;105(2):311-5. doi: 10.1542/peds.105.2.311. PMID: 10654947.
4. Otter JA, Yezli S, Salkeld JA, French GL. Evidence that contaminated surfaces contribute to the transmission of hospital pathogens and an overview of strategies to address contaminated surfaces in hospital settings. Am J Infect Control. 2013 May;41(5 Suppl):S6-11. doi: 10.1016/j. ajic.2012.12.004. PMID: 23622751.
5. Nseir S, Blazejewski C, Lubret R, Wallet F, Courcol R, Durocher A. Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the intensive care unit. Clin Microbiol Infect. 2011 Aug;17(8):1201-8. doi: 10.1111/j.1469- 0691.2010.03420.x. Epub 2010 Dec 13. PMID: 21054665.
6. Garvey MI, Wilkinson MAC, Bradley CW, Holden KL, Holden E. Wiping out MRSA: effect of introducing a universal disinfection wipe in a large UK teaching hospital. Antimicrob Resist Infect Control. 2018 Dec 19;7:155. doi: 10.1186/s13756-018-0445-7. PMID: 30574298; PMCID: PMC6299988.
7. Anderson DJ, Chen LF, Weber DJ, Moehring RW, Lewis SS, Triplett PF, Blocker M, Becherer P, Schwab JC, Knelson LP, Lokhnygina Y, Rutala WA, Kanamori H, Gergen MF, Sexton DJ; CDC Prevention Epicenters Program. Enhanced terminal room disinfection and acquisition and infection caused by multidrug-resistant organisms and Clostridium difficile (the Benefits of Enhanced Terminal Room Disinfection study): a cluster-randomised, multicentre, crossover study. Lancet. 2017 Feb 25;389(10071):805-814. doi: 10.1016/S0140- 6736(16)31588-4. Epub 2017 Jan 17. PMID: 28104287; PMCID: PMC5935446.
8. Halstead FD, Quick J, Niebel M, Garvey M, Cumley N, Smith R, Neal T, Roberts P, Hardy K, Shabir S, Walker JT, Hawkey P, Loman NJ. Pseudomonas aeruginosa infection in augmented care: the molecular ecology and transmission dynamics in four large UK hospitals. J Hosp Infect. 2021 May;111:162-168. doi: 10.1016/j. jhin.2021.01.020. Epub 2021 Feb 1. PMID: 33539934.
9. Garvey MI, Bradley CW, Wilkinson MAC, Bradley C, Holden E. Engineering waterborne Pseudomonas aeruginosa out of a critical care unit. Int J Hyg Environ Health. 2017 Aug;220(6):1014-1019. doi: 10.1016/j.ijheh.2017.05.011. Epub 2017 May 31. PMID: 28592358.
10. Garvey MI, Bradley CW, Holden E. Waterborne Pseudomonas aeruginosa transmission in a hematology unit? Am J Infect Control. 2018 Apr;46(4):383-386. doi: 10.1016/j. ajic.2017.10.013. Epub 2017 Nov 28. PMID: 29195780.
11. Beswick AJ, Fry C, Bradley CR, Pottage T, Sharpe S, Haill CF, Mugglestone MA, Bak A, Marsden GL, Bennett A, Garvey M, Wilson APR. Automated room decontamination: report of a Healthcare Infection Society Working Party. J Hosp Infect. 2022 Jan 24:S0195-6701(22)00011-1. doi: 10.1016/j. jhin.2022.01.006. Epub ahead of print. PMID: 35085677.

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Upcoming Events

Central Sterilising Club Annual Scientific Meeting

Crowne Plaza, Newcastle Upon Tyne
3rd - 4th April 2023


Hilton Birmingham Metropole
18th April 2023

Infection Prevention and Control 2023

National Conference Centre, Birmingham
25th - 26th April 2023

Access the latest issue of Clinical Services Journal on your mobile device together with an archive of back issues.

Download the FREE Clinical Services Journal app from your device's App store

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