Improving the Reliability of Adenosine Triphosphate (ATP) Testing in Surveillance of Food Premises: A Pilot Study.

Author:Whiteley, Greg S.


Each year in Australia, it is estimated that there are more than 4 million incidents of food poisoning due to poorly prepared or contaminated food (Food Safety Information Council, n.d.). There are complex and interlocutory standards including the Australian and New Zealand Food Standards Code 2016 and regional legislation (e.g., New South Wales Food Act 2003), which mandates compliance with the standards for hygiene and maintaining food safety.

Environmental health officers (EHOs) conduct routine site inspections of food preparation premises to ensure code compliance is maintained. Despite active surveillance across retail food preparation premises, the incidence of reported food poisoning events and industry compliance remains static (Food Authority New South Wales, 2017).

The current surveillance approach for hygiene establishes benchmarks on microbial limits of both specific and nonspecific microorganisms. While microbiological sampling is both specific and quantitative, it is also costly, requires rapid transport for laboratory analysis, and is subject to time limitations because culturing the results takes several days and further identification of the bacteria can take up to several weeks. Consequently, microbial sampling is actively discouraged for normal use by most EHOs, particularly in regional locations (Tebbutt, 2007). The use of microbiological sampling tends to be limited to statutory evidence collection or project work rather than routine surveillance of food premises.

Hygiene or cleanliness assessments therefore primarily must rely on qualitative information through the visual appearance of surfaces and implements used in food premises. The requirements for visual cleanliness are that "there is no accumulation of... food waste, dirt, grease, or other visible matter" (Australian and New Zealand Food Standards Code 2016, Food Safety Standard 3.2.2 and also section 19(1), (a) to (f)). The visual appearance measurements undertaken during a field assessment normally are applied through a standardized checklist intended to ensure that all possible items and matters are appropriately considered during each inspection. In some cases, a scoring system is also used with the checklist to compile a mini risk assessment (Food Authority New South Wales, 2018). The standardized food premises surveillance checklist can be completed either manually or via an electronic device such as a smartphone, tablet, or similar web-based tool.

There is a large evidence gap between visual inspection and microbiological sampling because normal human vision cannot determine the presence of microbial soils or food residues that are below the limit of detection by eyesight. EHOs need a reliable, quantitative, and real-time tool to assist in a more scientific basis of determining cleanliness and hygiene during inspections of food premises.

All living cells contain the molecule adenosine triphosphate (ATP), which cells use in the process of respiration (converting oxygen into an energy source). As a common molecule for all cells, including bacteria, food, and even human cells, ATP can be used as a surrogate for contamination of food surfaces, including the presence of bacterial cells (Griffith, Cooper, Gilmore, Davies, & Lewis, 2000).

Rapid ATP testing devices are used to detect cellular ATP through a swabbing process that then reacts luciferase with the ATP (liberated from the cells) and this reaction gives off light that is measured in the ATP testing device. The light given off is proportional to the reaction, thus quantitatively assessing the presence of ATP on a surface in just a few seconds after swabbing. The potential advantage for EHOs in using rapid ATP testing during surveillance of routine food premises is that the results are in real time, and there is no delay awaiting microbiological testing results.

Although ATP testing does not always correlate well with specifically proscribed microbial pathogens, in the context of normal surveillance of food premises, the broader result provides an indication of general surface uncleanliness. Uncleanliness can be a leading indicator for soils that can support pathogenic microbe survival on surfaces, and thus a better measure of uncleanliness could be an indication of noncompliance with the standardized codes.

The Issues for Field Use of ATP Testing by Environmental Health Officers

The use of rapid ATP testing has been suggested as an alternative, quantitative monitoring approach for food preparation surfaces (Griffith, Davidson, Peters, & Fielding, 1997). ATP testing has been shown to be superior to both visual inspection and microbiological sampling for general cleanliness and hygiene monitoring of a variety of surfaces in food preparation and in healthcare settings (Aycicek, Oguz, & Karci, 2006; Carrascosa et al., 2012; Griffith et al., 2000). ATP testing correlates well with 10-fold dilutions of microbial populations (Aiken, Wilson, & Pratten, 2011; Sciortino & Giles, 2013). ATP testing also has been used to assist with specific pathogen sampling as part of an integrated cleanliness monitoring method (Whiteley, Knight, et al., 2015).

There are quite a large number of studies where the usefulness of ATP testing has been demonstrated for on-site training due to the rapid feedback on surface cleanliness (Roady, 2015). ATP testing has even been used to assess menu cleanliness within the nonpreparation areas of food service establishments (Choi, Almanza, Nelson, Neal, & Sirsat, 2014). The field use of ATP testing by EHOs has been recommended, but problems with interpretation and reliability have thus far limited implementation by EHOs (Tebbutt, Bell, & Aislabie, 2007).

Rapid ATP testing devices, however, are subject to an array of confounders that diminish the reliability of ATP testing (Malik & Shama, 2012). The use of any testing approach for cleanliness monitoring in food preparation areas presents sampling issues with associated variance due to the subvisual and nonuniform distribution of soiling materials, including food residues and/or microbiological contaminants (Tebbutt, 2007). The variance of ATP testing includes disproportionate responses to "rich" food substances, which may also be randomly distributed on surfaces and implements (Bottari, Santarelli, & Neviani, 2015; Whitehead, Smith, & Verran, 2008).

It is quite easy to overstate the meaning of the results from ATP testing if only a single sample is taken from any one surface because there is a high level of underlying variance in the data. The results of sampling on this basis can be quite misleading and difficult to interpret (Shama & Malik...

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