The objective of this study by van Arkel, et al. (2021) was to determine the correlation between adenosine triphosphate (ATP) measurements and microbial contamination using a standardized method. Secondarily, analyzing reproducibility of ATP measurements and aerobic colony counts (ACC’s) on the same surface.

ATP measurements and ACCs were conducted on 10 pre-defined fomites in a hospital and nursing home setting. Per fomite two ATP measurements and two agar plate measurements were conducted, each measurement was conducted on a 25 cm2 surface. Both measurements were compared and analyzed for correlation.

In total, 200 paired measurements were conducted, 200 ATP measurements and 200 ACCs. The mean of all ATP measurements tested on the same surface was calculated, as was for all 200 ACCs. There was a strong correlation between the mean of two ATP measurements on two different sites on the same fomite (R = 0.800, p < 0.001) as well as between two ACC measurements on the same fomite (R = 0.667, p < 0.001). A much weaker correlation was found between RLU values and ACC’s (R = 0.244, p < 0.001).

The authors conclude, "Reproducibility of ATP measurements and ACCs on the same fomite was good. However, the correlation between RLU values and ACCs on hospital surfaces was much lower. This may be explained by the wide variety of biological material that is measured with ATP, of which the bacterial load is only one of many components. ATP measurement can be used to give a quantifiable outcome for the rating of cleanliness in health care facilities, however the results cannot be translated into the level of microbial contamination."

Reference: van Arkel A, Willemsen I, et al. The correlation between ATP measurement and microbial contamination of inanimate surfaces. Antimicrobial Resistance & Infection Control. Vol. 10, article number 116. 2021.