The Science and Technology of ATP

ATP is the primary energy transfer molecule present in all living biological cells on Earth. ATP cannot be produced or maintained by anything but a living organism, and as such, its measurement is a direct indication of biological activity. For hygiene testing the total ATP content of the sample is determined.


The purpose of ATP testing is to achieve and defensibly document effective cleaning by following the principle that if biomass is not present on critical surfaces after cleanup there is not enough medium for microbiological proliferation. Simply stated: no biological contamination, no microbial growth.


The main advantage of ATP as a biological indicator is the speed of the analysis. Unlike quantitative microbiological monitoring that requires at least several hours, quantitative biological monitoring takes only minutes from collecting the samples to obtaining the results. Results are given in real time.


Here is how it works: ATP is rapidly detected by light emission through the combined use of luciferase and a luminometer. An ATP free swab is moistened with an ATP free buffer, water or extractant. The use of the extractant helps releasing ATP from the surface being sampled. Using a portable luminometer, testing the swab is usually done immediately. There are some systems where the swabs are stable for a number of hours; thereby allowing the user to complete the analysis at a workstation or other location.


Note:   Although studies show there is often a correlation between ATP measurements and presence of live bacteria, ATP testing is not a substitute for plate counts and pathogen testing in healthcare environments, even though the temptation is there to use it as such in this age of expediency.


Interpretation of Results

There is a grave misunderstanding in our industry that the ATP monitoring system is a “bug test” when it really is a “dirt test.” I would be remiss if I did not advise you about some of the nuances of data interpretation. The test readout is in relative light units (RLUs), which mean the systems measure luminescent units, not cells. Remember, the luminometer detects bioluminescence from ATP, a cell constituent.

Forensic sanitarian Robert W. Powitz, Ph.D., MPH, RS, CFSP, is principal consultant and technical director of Old Saybrook, CT-based R.W. Powitz & Associates, a professional corporation of forensic sanitarians who specialize in environmental and public health litigation support services to law firms, insurance companies, governmental agencies and industry.


For more than 12 years, he was the Director of Environmental Health and Safety for Wayne State University in Detroit, MI, where he continues to hold the academic rank of adjunct professor in the College of Engineering. He also served as Director of Biological Safety and Environment for the U.S. Department of Agriculture at the Plum Island Animal Disease Center at Greenport, NY.


Among his honors, Powitz was the recipient of the NSF/NEHA Walter F. Snyder Award for achievement in attaining environmental quality, and the AAS Davis Calvin Wagner Award for excellence as a sanitarian and advancing public health practice. He is the first to hold the title of Diplomate Laureate in the American Academy of Sanitarians, and also is a Diplomate in the American Academy of Certified Consultants and Experts and with the American Board of Forensic Engineering and Technology.


Dr. Powitz welcomes reader questions and queries for discussion in upcoming articles, and feedback or suggestions for topics you'd like to see covered can be sent to him directly at [email protected] or through his website at