In hospitals across the nation, adenosine triphosphate (ATP) monitors are used to test surfaces for the presence of biological contamination. Armed with a swab and a hand-held device, anyone from an Infection Preventionist to an Environmental Services employee can easily sample a surface and quickly get feedback on the presence of organic matter. What many of these thousands of users may not realize, however, is that their ATP monitor works thanks to summer’s favorite insect, the firefly.
Most of us have childhood memories of summer evenings spent chasing the blinking lights of fireflies. In the soft twilight just after the sun sets, these flashes of light tell us that summer is here, but the glow tells fireflies that it is mating season. Using a combination of short and long glows, fireflies communicate information such as gender, species, and health to each other.
This “cold light,” which produces no UV or infrared frequencies, is created via a chemical reaction featuring the bioluminescence enzyme luciferase (named for a nicer side of Lucifer, the “lightbringer”). When this enzyme interacts with luciferin, an organic compound, and ATP, the result is a glow of bioluminescence. This reaction is visible in firefly larvae (glow worms), adult fireflies, as well as many other bioluminescent species.
So how did we get from glowing fireflies to detecting contamination? The link is ATP, or adenosine triphosphate.
ATP is often referred to as ”cellular currency.” It is present in the cells of every living thing on Earth, and serves as a coenzyme in metabolism. Essentially, ATP carries energy (fuel) to every part of the cell enabling every single chemical process that results in life. Wherever there are cells, there is ATP. And the opposite also applies: Where there is ATP, there are cells. If we could measure ATP, that would be a great indicator of organic contamination on surfaces surrounding patients. But how do we measure the presence of trace amounts of a microscopic substance?
This is where fireflies come in. Researchers developed a way to take advantage of the ability of luciferase to glow in the presence of ATP as a rapid way to detect the presence of organic matter. While accurate and reliable, swabbing and culturing a surface takes time. ATP monitoring may not be as accurate as swabbing and culturing, but it is a rapid indication of the presence of biological contamination, and a good place to start for those concerned with environmental cleanliness.
So how do they work? Regardless of brand or style, ATP monitors work by combining luciferase with a swabbed sample from the surface. The amount of light produced, measured by a luminometer inside the handheld device, indicates the amount of organic material present. It's that simple!
So thanks to our summer friend, the firefly, and the brilliance of Emmett W. Chappelle we have a quick and simple way to get feedback about the cleanliness of a surface.
Editor's Note: This post was originally published in June 2018 and has been updated for freshness, accuracy and comprehensiveness.