Using ATP to monitor surface cleanliness

Ten to 15 years ago it was often stated that there was no direct evidence of a link between Healthcare Associated Infections (HAIs) and the contamination on environmental surfaces in the patient care environment. It was known that pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile are present on environmental surfaces and can survive, but it was not known how much of a threat they represented. In other words, the degree to which environmental contamination contributes to the spread of HAI was unknown as direct evidence was lacking. In the intervening years there have been numerous academic studies published to show the impact that environmental surfaces play in the spread of HAIs and the contribution that a properly functioning, efficacious cleaning regime can provide to overall management of HAIs and containment of localised outbreaks of disease.1-4 Consequently, the prevailing advice from many advisory bodies and health authorities today is that maintaining a clean patient care environment underpins a wider infection prevention programme and should be an integral part of HAI reduction activities.5 An example of this is the publication from the UK Department of Health (DH); Health and Social Care Act 2008: Code of Practice on the prevention and control of infections. This states that to minimise the risk of infection a hospital must designate leads for environmental cleaning and that all parts of the premises from which care is provided must be kept clean. Moreover, the UK DH publication in 2008, Clostridium difficile infection: How to deal with the problem, states that environmental cleaning of rooms or bed spaces of C. difficile patients should be carried out at least daily and that all clinical areas should be regularly assessed for cleanliness and results fed back to clinical and cleaning teams. If we now make the assumption that cleanliness of patient care areas is not only desirable but is an essential infection prevention requirement, how can the dayto- day standards of cleanliness achieved be monitored and improved? How can cleaning quality assurance be best implemented? The verification process for deciding whether a surface is sufficiently clean is currently overwhelmingly carried out by visual inspection – a person will look at a surface and decide whether it is acceptable or whether it should be recleaned. This method produces fast results and is of relatively low cost but is inherently insensitive, subjective and offers no real quantification.6 Visual inspection is often complemented by periodic microbiological sampling to understand the nature of microbial residues in patient care areas. However, in more recent years, other rapid method technology, such as ATP (adenosine triphosphate) bioluminescence, has been employed for cleaning verification. A recent study by Sherlock O et al carried out an evaluation of the efficacy of four methods for determining hospital cleanliness.6 These were visual inspection, two types of microbiological analysis (total aerobic colony count and MRSA) and ATP bioluminescence. The results showed that the ATP method recorded the least number of surfaces as being clean compared to the visual and microbiological assessment methods. The authors concluded that “visual methods to evaluate cleanliness are subjective and inadequate” and that “the use of rapid methods such as ATP bioluminescence monitoring in a hospital setting should be considered.”

Technology principles

Before we further explore the potential benefits of ATP bioluminescence, let us look at the principles and basic functionality of the technology. ATP is the basic energy molecule for all metabolising animal, vegetable, bacterial, yeast and mould cells. It is therefore a good marker to indicate whether something of biological origin is present on a surface or in a sample. If a surface has been cleaned to a good standard there should not be much ATP left behind after the process. If cleaning has been ineffective or a surface has been missed entirely then ATP will be left behind and can be detected and quantified rapidly by means of ATP bioluminescence. It will not distinguish between which source the ATP originates from (and in a hospital environment the majority of ATP present will probably emanate from a human source) but it does provide a quantitative result in less than one minute in Relative Light Units (RLU). This quantification will provide a definition of what “clean” is and can therefore allow thresholds to be set and minimum standards to be implemented. If results exceed the set thresholds then a corrective action of re-cleaning can implemented. This would be particularly important for high risk surfaces. Considering this technology will detect ATP from all sources, it is important to note that ATP bioluminescence results will not correlate with microbiology results in environmental samples. This is because microbiology is measuring only the microbial part of environmental contamination, while ATP is measuring the total load of biological contamination, both microbial and non-microbial.