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What should we expect from the use of disinfectants in hospitals?

Curtis G Gemmell
Professor of Bacterial Infection and Epidemiology
Division of Immunology, Infection & Inflammation
Medical School
University of Glasgow

Hospital-acquired infection (HAI) is at an all-time high in UK hospitals. That this is the reality is something we should be concerned about whether we are hospital clinicians, medical microbiologists, nursing staff, hospital administrators, patients or their relatives/friends who visit. Much has been said and written about the cleanliness or otherwise of our hospitals, and while it is generally accepted that our hospitals are not as clean as they might be, we should remember that the patients occupying beds and the bacterial causes of infection are different from 10 or 15 years ago. More and more patients are entering our healthcare system with increasingly complex underlying medical conditions, making them more and more susceptible to infection. In addition, many of the bacterial causes of HAI have developed resistance to antibiotics – methicillin-resistant staphylococci, glycopeptide-resistant enterococci or extended-spectrum beta-lactamase (ESBL) producing Gram-negative bacteria – rendering ineffective many of the first-line drugs used in treatment.

Risks for the emergence of multiply resistant bacteria include length of hospital stay, previous exposure to antibiotics, especially those with a broad spectrum of activity, and breakdown in infection control procedures. Such “superbugs” have become endemic in many of our hospitals, and the chances of their spread from patient to patient have increased the risk of acquisition of HAI on entering hospital. Infections due to MRSA are associated with an increase in morbidity/mortality despite adequate therapy.(1–3) We recognise also that increased use of antibiotics both in treatment and prevention of infection has contributed to their prevalence not only as infective agents among patients but also as transient components of the normal microflora of healthcare workers (HCWs) and the environment in which they work.

The high incidence of HAI (estimated at between 1 in 8 and 1 in 10 admissions in the UK) has resulted in a plethora of pronouncements from government and its agencies, new protocols and guidelines, and the development of sophisticated infection-control procedures. It is clear that such measures are not meeting with instant success, mainly due to the underlying high incidence of HAI, but also due to their complexity and noncompliance by HCWs.

Rather than trying to achieve unachievable targets, we should be trying to manage down HAI levels in high-risk areas of our hospitals as a priority before attempting to eliminate HAI throughout. In recent years we have seen the development and in-use testing of a variety of disinfection practices to control HAI outbreaks, ranging from alcohol-containing gels for hand cleansing, through medical devices incorporating antibacterial agents, to deep-cleaning and ozone or hydrogen peroxide fumigation of individual isolation rooms or whole ward areas.

Most infection control policies concentrate on minimising the risk of transmission of infection between patients by emphasising the important part that clean working practices amongst HCWs can play. A report by the British Medical Association published in February 2003 and updated in May 2007 emphasised that one component of the Standard Infection Control Procedures (SICPs) should be to “ensure that the care setting is adequately cleaned to prevent occurrence of cross infection”. There is good correlation between strongly controlled infection-control programmes, appropriate antibiotic consumption and reduction in incidence of antibiotic resistance and HAI, but compliance, especially in regard to handwashing/disinfection, is one area that readily breaks down under pressure of a high workload, sometimes reaching only 50–60%, and exacerbated by staff shortages.(4,5) Hitherto, not enough attention has been given to the cleanliness or otherwise of the hospital environment.(6) Superficially clean hospital wards are not necessarily microbiologically clean. Routine cleaning by domestic staff removes superficial grime but may or may not involve the use of disinfectants to kill invisible bacteria and viruses. Even if disinfectants are used they may not be used correctly (ie, ensuring that correct concentrations of freshly prepared solution are used or making allowance for the different surfaces being treated). Several studies have shown that three of the major causes of HAI (C difficile, MRSA and noroviruses) survive in the hospital environment.

A real step forward in our fight to control HAI would be to eliminate the environmental source of these microorganisms. We need to look more closely at the way in which we evaluate the efficacy of disinfectants and the ways in which bacteria develop resistance to them. Most disinfectants have been developed to kill bacteria, but not all kill viruses or bacterial spores. Their in-use efficacy can be compromised by the presence of other organic matter and may not work as effectively as laboratory tests suggest on dried deposits. Most of the standard tests for disinfectants are based on the use of suspensions of microorganisms. This is not the real situation in which the agents will be used. Continuous use of individual disinfectants may (as found with antibiotics) lead to the development of resistance through the emergence of insensitive target enzymes or to more complex efflux pumps. Also, little or nothing is known of the residual efficacy of a disinfectant – how long does it remain biologically active on treated inanimate surfaces? The real efficacy of a disinfectant may depend not only on its potency per se, the concentration at which it kills in vitro, but also on the length of time it may retain this potency in practice. Formulations of disinfectants that show residual activity for several hours or even days after application may offer significant advantages over those that do not. Such residual agents may, instead of being removed or inactivated during normal circumstances, build up following regular application.

Disinfectant study
One study carried out in Glasgow Royal Infirmary, UK, in 2005/06 illustrates the importance of such residual activity of a disinfectant in the control of MRSA infection through control of environmental levels of MRSA.(2)

Two ward areas within the Vascular Surgery Unit, which had a historically high incidence of MRSA infection (4–6 cases per month), were chosen for this study. One area of the ward comprising a six-bed open unit and two single rooms (test disinfectant area: TDA) was compared with a similar area of the same ward comprising one six-bed open unit and one single room (control area: CA). The six-month study period included a total of 234 occupied beds in each of the 15 bed spaces. A bed-occupancy rate of >85% pertained throughout the study period. On admission to the ward, patients were screened for carriage of MRSA and any possible infection was followed up. Patient occupancy of the individual bed spaces and movement within and out of the ward was logged daily and recorded in relation to MRSA status.

Both areas were cleaned according to normal hospital cleaning procedures. In addition, all high-contact areas – television control handsets, patient call systems, bedrails, door handles, lockers, table tops and water taps – in the TDA were cleaned with wipes containing the Byotrol product A1616 once daily. The disinfectant contained two quaternary ammonium compounds and a biguanide in alcohol and attached to a polymeric backbone structure.

Environmental swabs were taken from all the high-contact areas once each week and cultured on a new chromogenic agar, which directly allowed the identification of likely colonies of MRSA. Each week 74 sites were sampled. Blood pressure cuffs used generally in the ward were also swabbed each week, as they were thought to be a potential cause of cross-infection. During the 10th week, each of the six-bed rooms, control and test, tested positive for MRSA: in the test six-bed room, four sites with MRSA E15 and two with gentamycin-resistant strains; in the control six-bed room, eight sites with E15 MRSA and seven sites with gentamycin-resistant strains (Figure 1).


After four months (about 17 weeks) a switchover took place in which the test disinfectant was applied in the CA and normal cleaning procedures resumed in the hitherto TDA. In stage one, a total of 48 sites (7.0%) in the TDA and 69 sites (12.3%) in the CA disclosed the presence of MRSA. This represents a 50% reduction in number of sites contaminated with MRSA following additional disinfection treatment of one-fifth of surfaces in the relevant ward area (Figure 2). Tests in the 26th week showed the new CA to have seven sites with gentamicin-resistant strains, including three in the control single room, and in the new test rooms three gentamicin-resistant strains were detected, with two in the test single room.


In stage two, roughly equal numbers of positive isolations of MRSA occurred in each area. This converted into an incidence of 6.8% in the former TDA and 9.0% in the former CA. Environmental MRSA monitoring of individual bed spaces led to the detection of four new carriers of MRSA. Ten cases of nosocomial MRSA infection occurred in the first four-month period of this study, of which six were in the CA; this did not reach significance, but might have if the switchover had been delayed for perhaps another two months.

This study in two similar areas of a single ward did show that it was possible to reduce MRSA infection rates by the addition of a single intervention (regular disinfection of high-contact sites) to the ongoing infection control practices of the hospital. Extension of the study for a longer period of time and to the other high-risk areas of the hospital is likely to be rewarding.

A single intervention may not be enough to solve the problem of HAI, but its addition to the “bundle” of infection control procedures might make clean hospitals really clean! The Byotrol technology allows the simultaneous application of more than one disinfectant (in this case, two quaternary ammonium compounds and a biguanide) and subsequent residual activity via a carrier together with the possibility of “mixing and matching” biocides to suit the nature of the indigenous hospital pathogen and its resistance profile to antibiotics and biocides. The cost-effectiveness of any component of an infection control programme can really only be accurately measured by a significant reduction in incidence of HAI. Unfortunately the Glasgow Royal Infirmary study just failed to reach a significant difference between the treatment and control areas in this respect, although there was a significant difference in incidence of environmental contamination with MRSA (12.3% in control area, as compared with 7% in treated area).

Whilst there are national standards for hospital ward cleaning, along with recommended frequencies of cleaning procedures, these rely on visual inspection to judge the effectiveness of the cleaning regimen. This study has shown that an additional cleansing step can influence the incidence of environmental MRSA in a ward. Only one other study that has evaluated microbiologically the efficacy of hospital cleaning methods concluded that traditional mopping and vacuuming was not sufficient to reduce environmental bacterial loads.(7)


  1. Cosgrove SE, et al. Comparison of mortality associated with methicillin-resistant and methicillin-susceptible Staphylococcus aureus bacteremia: a meta-analysis. Clin Infect Dis 2003;36:5-9.
  2. Gemmell CG, Ferguson M, Mead A, Hamilton CM, Dandalides P. High contact sites in wards as sources of MRSA contamination. Poster presented at International Hospital Infection Control Meeting, Amsterdam, 2006.
  3. Health Protection Scotland. Report on methicillin resistant Staphylococcus aureus bacteraemias in Scotland January 2003–September 2006.p. 1-18.
  4. Pittet D, et al. Effectiveness of a hospital-wide programme to improve compliance with hand hygiene. Lancet 2000;356: 307-12.
  5. Pittet D, et al. Cost implications of successful hand hygiene promotion. Infect Control Hosp Epidemiol 2004;25:264-6.
  6. Boyce JM, Potter-Bynoe G, Chenevert C, King T. Environmental contamination due to methicillin resistant Staphylococcus aureus. Possible infection control implications. Infect Control Hosp Epidemiol 1997;18:622-7.
  7. White LF, Dancer SJ, Robertson C. A microbiological evaluation of hospital cleaning methods. Int J Environ Health Res 2007;17:285-95.