Why is ATP Testing Important?

By Cole Barnett, (ASU Bio-Engineering Student & AZ-BIO Fall 2020 Intern)

While the majority of Joe’s Az-Bio customers can visually see the good job, we do cleaning and sanitizing, others have requested to see quantitative numerical test results as proof of disinfection. This is especially relevant during the COVID era of cleaning. The test that we use most often is the ATP test.

The acronym ATP stands for Adenosine Triphosphate, which is arguably one of the most important molecules for all living things from bacteria to humans.

ATP is like the currency for energy for cells; it is what living things use to “spend” energy. It is a relatively unstable molecule that is created by the breakdown of food in animal cells and by the absorption of sunlight in plant cells.

This is an important fact because it means that it can only ever be found in or around cells, and this makes ATP a good measurement of biological activity and growth.

This is why ATP testing is used to measure general cleanliness; it detects the presence of any live bio-contamination, whether that be bacteria, fungi, or mold. Interestingly, it cannot actually directly measure the presence of viruses because viruses do not produce ATP.

Viruses are not cells; they are just floating pieces of DNA ready to hijack cells they come into contact with. Although ATP testing cannot detect viruses themselves, a low ATP test shows that the surface has been thoroughly cleaned.

This means that the likeliness of a virus still being alive on the surface is extremely unlikely.

The ATP test itself works in a clever way.

The particles or fluids on the surface being tested are combined with a naturally occurring chemical found in fireflies (luciferase). If ATP is present, it will energize the luciferase, and the reaction will emit a measurable amount of light.

A lot of ATP means a lot of light, a little bit of ATP means a little bit of light, and no ATP means no light.

This is measured inside the meter and converted to a number which we can read and interpret.

So, why are we reading some ATP values that aren’t zero even when we have cleaned with professional-grade disinfectant cleaners?

One answer could be that dead cells release their ATP, so even though the cells are dead and inactive, their ATP could still be being measured.

Another answer could be explained by biofilms.

Bacteria are impressive organisms and even though they are individual organisms, they can actually communicate with each other and act as a group to be stronger together instead of acting as a bunch of weaker individuals (here’s a video on Quorum sensing: Bacteria talks)

Biofilms are another example of this.

The individual cells stick to each other and to the surface they are on, and then they secrete a slimy material over and around them which glues them in and protects them.

This makes them significantly harder to remove and presents a dangerous source of contamination.

An example of biofilms is plaque on teeth which can turn into tartar if not brushed away quickly.

Tartar can only be removed by a professional dental cleaning because stubborn biofilms cannot be treated by chemicals alone, but rather they need to be physically broken into and removed before any cleaning agents would be at all effective (Stewart, par. 6 &12).

So how do we get lower ATP numbers?

Unfortunately, the answer may be more elbow grease. Using the right tools for the job could also be very helpful as a tougher brush may clean surfaces and get into biofilms better than a paper towel in appropriate situations.

Another useful suggestion may be to wipe or scrub surfaces down first and then spray so that the disinfecting drops can go directly onto the surfaces and not get blocked by dirt, oil, or intact biofilms.